CHEM 241 Final Exam
Why do large solutes move slower in capillary electrophoresis?
More friction
Why is a photomultiplier tube so sensitive?
More than 10^6 electrons are collected for each electron striking the first surface
What is pulse width like in the acute phase?
Much greater than normal
Why are CF patients at chronic risk of infection?
Mucus leads to chronic infection because bacteria can form biofilms inside of the mucus
What is MAHMA?
NO donor
How does nitric oxide compare to the antibiotic tobramycin?
NO is 100x more effective under anaerobic conditions
How does nitric oxide work as an antibacterial?
NO reacts on the outside with another mole of NO and O2 to form dinitrogen trioxide which can cause problems to the proteins in the bacterial membrane NO can diffuse across the membrane to form superoxide to form peroxinitrite which causes: lipid peroxidation, tyrosine nitrate, oxidative DNA cleavage
If a molecule does not absorb light, can we get fluorescence?
No
What is white noise?
Noise with no frequency dependance
What is reverse phase chromatography?
Nonpolar stationary phase with a less non polar mobile phase
In gas chromatography, what type of column is used?
OTC or packed columns
What are gratings?
Optical elements with closely spaced lines
When are optical fibers helpful to use?
Optical fibers can bring an optical signal from inside a chemical reactor out to a spectrophotometer for monitoring. This can be especially helpful it we are dealing with dangerous things
What is stimulated emission?
Organized photon emission in a lase. The emitted photon1 has a certain wavelength and energy and the photon1 strikes an atom with an electron in the same excited state and stimulates emission so photon2 is emitted with the same frequency and direction of photon1 because of constructive interference. This starts an avalanche of photons as it travels through the laser
What is the light leaving the sample?
P
If there are light absorbing molecules in a given sample, what will be the values of P and P0?
P will be smaller than P0
Absorbance is independent of what that intensity is dependent on?
P0
What is the light entering the sample?
P0
How is a blank measured in a single beam spectrophotometer?
P0 is not measured directly, but it is measured as the irradiance of light passing through a blank cuvet containing pure solvent and then the blank cuvet is removed and replaced with one containing the sample and the irradiance of light hitting the detector after it passes through the sample is P. The blank cuvet compensates for reflection, scattering, and absorption by the cuvet and the solvent
I is dependent of what and what can we do with this?
P0; therefore, increasing the power of the light entering the sample does give more fluorescense of phosphorescense
What is irradiance/power?
P; energy of a beam that reaches a given area per second
What type of column is used in HPLC?
Packed column
Why do OTC result in shorter analysis times?
Particles in a packed column resist flow, so the linear velocity is slower in packed columns
What is diabetes?
Patients are deficient in insulin production and patients cannot regulate blood glucose and are hyper and hypoglycemic all fo the time and this leads to a lot of problems
How was the issue with the glucose sensors not giving any response fixed?
Peel off the outer layer of the sensor, grind it up really small and embed particles that store and release NO in the outer membrane of the sensor. This makes it so that the entire sensor will no longer be modified by the nonporous coating and glucose could leech in
What types of solvents are used in reverse phase chromatography?
Polar; methanol, acetonitrile and water
How does a grating monochrometer work?
Polychromatic radiation from the entrance slit is collimated (made into a beam of parallel rays) by a concave mirror. The rays fall on a reflection grating, whereupon different wavelengths are diffracted at different angles. Then, the light falls on a second concave mirror, which focuses each wavelength at a different point on the focal plane. The orientation of the reflection grating directs 1 narrow band of wavelengths out of the exit slit
For a reverse phase HPLC separation with a mobile phase pH 3, which compound would elute first and why? Propanoic acid (CH3CH2COOH, pKa 4.87) or propylamine (CH3CH2CH2NH2, pKa 10.57)
Propylamine because under its pKa it will be protonated and will be charged and charged species will not interact well with the non polar stationary phase
What happened when we modified the R-group chain length on the chemically modified pacemaker electrode?
Pulse width went way up in the acute phase and stayed relatively high in the chronic phase
What was the new class of electrically conductive sensors for pacemakers?
R-groups with defects, Au, Pt-Ir
What is internal conversion
Radiationless transition between states with the same spin quantum number (S1 to S0). It transfers energy to neighboring molecules through collisions
What is the order of the electromagnetic spectrum from least to most energetic?
Radio, microwave, infrared, visible, UV, x-rays, gamma rays, cosmic rays
What is Raman spectroscopy like?
Raman is related to vibrational spectroscopy like IR
What is a linear range of a GC detector?
Range of concentrations where the peak areas are directly proportional to the concentration of the analyte in the sample.
What is the most common elution method in HPLC?
Reverse phase chromatography
Electronic levels are labeled as what?
S0, S1, S2
What is the lowest energy singlet state?
S1
How does a flame atomize?
Sample is drawn into the nebulizer by air. Nebulizer creates an aerosol from the liquid sample. Droplets entering the flame evaporate, the remaining solid vaporizes and decomposes into atoms
Why is scar tissue formation around pacemakers a bad thing?
Scar tissue is not excitable, and it decreases electrical stimulation efficiency, so we need a longer pulse width
What are ideal detectors to use in HPLC?
Sensitive to low concentrations of many analytes, linear response, insensitive to temperature and solvent changes
What are advantages to ICPMS?
Sensitive, selective, few chemical or spectral interference
What is capillary zone electrophoresis?
Separation is based on differences in electrophoretic mobility.
What is silanol?
SiOH
What is the quality of a signal referred to as?
Signal to Noise Ratio (S/N)
What is the equation for signal and what are the variables?
Signal=KP+K' Signal: output electrical response in amps or volts K: propprtionality factor that determines sensitivity P: photon flux (lioght power K': dark current
What is p-type silicon?
Silicon that has been doped with chemicals that makes it have less electrons than Si. It is + hole rich and positive
What is n-type silicon?
Silicon that has been doped with chemicals that makes it have more electrons than Si. It is electron rich and negative
Rate of migration in capillary electrophoresis depends on what?
Size of solute and the charge of solute
How to decrease Eddy diffusion when using a packed GC column?
Small, uniform particle size, but this will require higher pressure because the smaller the article size, the less space in between particles, so the greater pressure is needed to force the mobile phase through the column
What type of molecules will move faster in capillary electrophoresis?
Smaller molecules and those that have a greater charge
What is the stationary phase in GC?
Solid particles or non-violating liquid
What is isocratic elution?
Solvent or solvents stay constant throughout the entire hPLC
What causes tailing?
Some solute is retained more strongly on the stationary phase
What type of solvents must be used with HPLC?
Special HPLC grade solvents
What is a wall coated open tubular column?
Stationary liquid phase 0.1 to 5 um thick on the wall of the column
What does Human Chorionic Gonadotropin do?
Stimulation of Corpus Luteal Progesterone Production
What is apparent mobility?
Sum of electrophoretic mobility plus electroosmotic mobility of the ion
What is the lowest energy triplet state?
T1
How does the energy of T1 compare to the energy of S1?
T1 is lower in energy than S1
What is transmittance?
T; the fraction of the original light that passes through the sample
What is resolution?
The ability to separate 2 closely spaced peaks.
Absorbance is the sum of what?
The absorbance at any wavelength of a solution containing any number of species is the sum of absorbances of all species in the solution
What happens if in capillary electrophoresis, the silica is capped with an amino group with a pH of 10?
The amino group will be protonated at a pH 7.4 and it will attract negatively charged groups. This will completely reverse the direction of electroosmosis and the movement will be towards the anode
What is the benefit to using microporous silica as the stationary phase support in HPLC?
The benefit to making it microporous instead of just using solid silica is it significantly increases surface area. With pores running through the silica, you end up with 99% of surface area inside the pores. More surface area=more stationary phase=better separation
In SEC, if we have a Kav greater than 1, what does this mean?
The biomolecule is interacting with something else other than going into the pores...it might be absorption.
What is electroosmosis?
The bulk flow of fluid in a capillary caused by migration o the dominant ion in the diffuse part of the double layer toward the anode or cathode
What do catheter O2 sensors look like as control or when they are doped with MAHMA/N2O2?
The control is covered with RBCs, platelets, and clots, and the MAHMA is not as much
What happens if the egg is not fertilized?
The corpus luteum and uterine lining atrophy and menstruation
In capillary electrophoresis if the silica is capped with an amino group with a pH of 10, where should the detector be?
The detector needs to be near the anode because this is the direction things are flowing now
What dictates the wavelength of the emitted photon?
The energy transition from the electron in the excited energy level to the ground energy level
What is an eluent?
The fluid that is entering the column
The amount of light absorbed by a given substance is dependent on what?
The frequency of the light (λ)
What causes electroosmotic flow in capillary electrophoresis?
The fused silica capillary has exposed Si-OH groups that are deprotonated at a pH of 2. The buffer is PBS which has positively charged sodium ions and they build up on the negatively charged wall. These move becasue there is an electric field from the anode to the cathode and this causes the entire mobile phase to move.
Why is it important that detectors are insensitive to temperature changes in HPLC?
The heat and AC can turn on and off
What does it mean to provide coherent light?
The light is really focused because of spatially and temporally constant inferference...all waves oscillate in phase with one another; so it can travel long distances
What is blackbody radiation?
The light that is emitted when an object is heated and emits radiation and glows
What is the smallest plate height we can get for a given particle?
The lowest your plate height can get is about 2x the stationary phase particle diameter
What type of nitric oxide donor gave a lower bactericidal dose? Why?
The macromolecule! The macromolcular scaffold attaches to the bacteria, so the NO delivery was more localized. This is because most bacteria are negatively charged and the macromolecule at pH 7.4 is positively charged because of amines, so electrostatics bring them together
What is dispersion?
The measure of the ability to separate wavelengths through the difference in the rerflecting angles
Why is high pressure needed in HPLC?
The particles are very fine
How does gradient elution alter partition coefficient?
The partition coefficient for all solutes changes based on the solute and stationary phase interacting
In partition chromatography, what determines how much time the solute will spend in each phase?
The polarity it is most like
What is the size of pores in microporous silica?
The pores must be large enough for solvent and solute to fit into them. 6-12 nm pores are typically required.
What is elution?
The process of passing liquid or gas through a chromatography column
What is relative retention/separation factor?
The ratio of adjusted retention times
What is emission of light?
The release of energy
What is the behavior of oxygen sensing for the MAHMA/N2O2 after time?
The response times are good, NO does not affect oxygen reading until about 15 hours when NO is gone
What is Kovat's Retention Index and why is it useful in GC?
The retention index of a certain chemical compound is its retention time normalized to the retention times of adjacently eluting n-alkanes. While retention times vary with the individual chromatographic system, the derived retention indices are quite independent of these parameters and allow comparing values measured by different analytical laboratories under varying conditions
What is Vr for SEC?
The retention volume
What is annoying about using a single beam spectrophotometer?
The sample and the reference must be placed alternately in the beam bcause we need to make a blank in order to get the correct absorbance values and if we are making measurements at multiple wavelengths, the blank must be placed between each sample
How is an emission spectra measured?
The sample is irradiated at one wavelength and emission is observed over a range of wavelengths. The emission monochrometer is positioned 90˚ to the incident light to minimize the intensity of the scattered light reaching the detector. We scan through the emitted radiation and the emission spectrum shows intensity vs. emission wavelength
What is extraction?
The separation of solute from 1 phase to another using two immiscible liquids (usually aqueous/organic solvent combos)
Why is it advantageous to use smaller particles?
The smaller the particles, the more particles that can fit and the more particles that are packed within the column, the better we can get separation because there are more attractions at the stationary phase. Decreasing particle size increases the number of theoretical plates, increasing resolution. It increases number of plates because it decreases Eddy diffusion and makes less time for equilibration so it decreases the C term. It also allows the optimum flow rate to be faster because the C term is smaller and we can use detectors with a lower detection limit because the analyte is not diluted
If it is advantageous to resolution to use small particles, why do we not make our particles infinitely small?
The smaller we make particles, the less likely we are to make them uniform, which will cause Eddy diffusion if they are not uniform. The smaller the particles, the greater the pressure needs to be to get a decent flow rate. We can also only make them so small
What are the problems with porous silica beads?
The solute can go straight through and be on the stationary phase for a long time and cause band broadening.
What are the requirements of a UV-Vis spectrometer?
The solute must exhibit absorption in the UV-Vis range and there must be no absorption by solvent
How does a phototube detector work?
The surface of the cathode is photosensitive, and it will emit electrons when it is struck by light. The anode will collect the electrons and when the electrodes go from the cathdoe to the anode, this generates a current and we measure this current
What is temperature programming?
The temperature is raised during the separation to decrease the retention times of later eluting components. If the temperature is low, the less volatile compounds may not elute.
What is Vm in SEC?
The total volume of the column, which includes solvent inside and outside of the gel particles
How does a tungsten lamp work?
The tungsten filament approaches 3000K
How does the hollow cathode lamp work?
There is a bias between the anode and cathode that generates excited state metal atoms. The detector at the right of the flame measures the amount of light that passes through the flame. The atom absorb part of the light from the source and the remainder of the light reaches the detector
How can optical fibers carry light by total internal reflectance?
There is a high-refractive index transparent core enclosed in a a lower-refractive index transparent cladding. Due to Snell's Law sinθr=(n1/n2)sinθi and if n1/n2 > 1 there is a range of angles in which all light is reflected at the walls of the core and a negligible amount enters the cladding and almost all rays entering one end of the fiber within a certain range will energy from the other end of the fiber with little loss
Why do greater charged molecules move faster in capillary electrophoresis?
There is an increased force
In looking at tissue inflammation analysis, compare NO-releasing glucose biosensors to controls.
There is less collagen density and less inflammatory cell density in the NO-releasing sensors
Why is capillary electrophoresis so fast?
There is no A or C term, only the B term to determine plate height, and the B term is reduced by a faster velocity
What are the interactions in affinity chromatography?
They are a combination of hydrophobic, electrostatic, and hydrogen bonding
What are conductometric detectors?
They are an electrochemical detector that measures the conductivity of the solvent
What are potentiometric detectors?
They are electrochemical detectors that monitor changes in the electrochemical potential
What happens to conventional intra-arterial sensors that measure blood-gas/electrolytes? Why?
They are initially accurate, but then they deviate from the true readings becase the body responds to artificial surface by platelet adhesion and this forms a clot on the sensor. Thus, you are no longer measuring O2 in the blood, we are measuring O2 of the clot. In addition, the body is vasoconstricting hopefully to clear the clot and every time it constricts we are not measuring O2 in the blood, we are measuring it in the constructed artery
How to absorption and emission spectra compare?
They are mirror images of each other, but the emission spectra comes at a higher wavelength
What are dynodes?
They are surfaces that produce many electrons in a photomultiplier tube
What are amperometric detectors?
They are the most common type of electrochemical detector. They apply a known potential and monitor the oxidation and reduction of a redox active species
What are the issues with refractive index detectors?
They are useless in gradient elution because changing the mobile phase will also change the refractive index and you will not be able to tell which change is from the change in solvent or change in the solute, you need a reference cell because it is temperature sensitive, the detection limit is 1000x less than UV-Vis
In normal phase HPLC, what is the behavior of non polar molecules?
They fly off of the column because they have nothing to interact with. There is no separation
In reverse phase HPLC, what is the behavior of polar molecules?
They fly off of the column because they have nothing to interact with. There is no separation
What are special about labels used to make fluorescense or phosphorescense measurements?
They have high molar absorptivity value and lots of double bonds and pi electrons
What are the challenges associated with developing implantable electrochemical sensors?
They need to be miniature in size, compensate for temperature variation, fast response time, and biocompatible, meaning the body will not have a foreign body respons
What is the purpose of the mirrors in a laser?
They reflect the avalanche of photons back and forth across lasing medium, which continues to stimulate emission of photons. The 2nd mirror lets some light out
What do filters do?
They remove certain wavelengths of radiation and only let the first order of light through
Gratings and prisms do what?
They separate out the full spectrum of light
Downsides of thick films of stationary phase in GC
Thick films of stationary phase can shield analytes from the silica surface and reduce tailing, but they can increase bleed (decomposition and evaporation) of the stationary phase at high temperatures
What is affinity chromatography used for?
To isolate a single compound from a complex biological mixture via specific binding of that compound to the stationary phase
To reduce the tendency of stationary phase to bleed at high temperatures, what is done?
To reduce the tendency of stationary phase to bleed at high temperatures, it is usually bonded to the silica surface and cross linked to itself
What is chromotography used for?
To separate compounds of a mixture, to identify components of a mixture, and for preparative purposes...to purify a large quantity of a component of a mixture
What causes scattering?
Too high of concentration of the solute
What causes overloading?
Too much solute (too high of a concentration) overloads the column. As solute builds up, it gets more soluble in the stationary phase and the stationary phase ends up looking like solute. This means that once the stationary phase starts to look like solutes, other solutes that come by later will not have the same partition coefficient and K goes way down...when solute starts to interact with solute there really is no stationary phase so it just all comes off which is why the peak drops so rapidly
T/F: An advantage of a double beam instrument over a single beam instrument for collecting absorbance spectra is the speed in which you can collect a spectrum
True
T/F: Decreasing the slit width on a monochrometer improves the ability to resolve closely spaced spectral peaks
True
T/F: Johnson noise is both random in direction and independent on frequency
True
True/False. Fluorescence lifetimes are shorter than phosphorescence lifetimes because the electronic transition for fluorescence is a singlet to singlet transition whereas phosphorescence requires a triplet to singlet transition
True
True/False. The resolution of a grating is proportional to the number of grooves it has
True
What type of light does a deuterium arc lamp give off?
UV
Fused silica cuvets can be used for what wavelength range?
UV and visible
What type of frequencies are used in atomic absorption?
UV or visible
What region of the light spectrum can cause fluorescence or phosphorescense?
UV vis region
What type of detectors do we use in capillary electrophoresis?
UV-Vis, fluorescence, mass spectrometry, electrochemical
Why is it not a good idea to use spectroscopy at high temperatures?
Undesired reactions may happen and this will cause more impurities
Thermal conductivity detectors are useful for what type of columns?
Useful for packed columns, but less sensitive than other detectors for OTC
How does HPLC work?
Uses high pressure to force solvent through closed columns containing fine particles that give high resolution separation
What is gradient elution?
Using 2 different solvents and increasing the amount of solvent B added to solvent A during the separation to create a continuous gradient
Absorption spectroscopy allows us to do what?
Using light and chemical measurements in order to qualify, detect, characterize different molecules
What do spectrophotometric methods do?
Using light and chemical measurements in order to qualify, detect, characterize different molecules
How do we relate frequency and wavelength?
Using the speed of light
In the electrophoretic mobility equation, what is E?
V/m
Rotational levels exist between what?
Vibrational levels
What is the fist process that occurs after absorption?
Vibrational relaxation to the lowest vibrational level
Electronic excitations require what type of light?
Visible light or ultraviolet
How does a refractive index detector work?
Visible light passes through the cell and is directed at a photodiode array. When a solute with a different refractive index than the solvent enters the cell, the beam is deflected and different pixels of the array are irradiated
What happens in gas chromatography?
Volatile analytes are vaporized and transported through the column by a carrier gas
If the solute is larger than the pores in SEC, what is Kav?
Vr=V0 and so Kav=0
If the solute is small and penetrates all of the pores in SEC, what is Kav?
Vr=Vm and Kav=1
What is the most common type of open tubular column in GC?
Wall coated
How was baby gender determined in ancient Egypt?
Water bags of wheat and barley. Grain type indicated gender
How was pregnancy determined in ancient Egypt?
Water bags of wheat and barley. if they germinated it meant pregnancy
Why does cooling a detector create less Johnson/Gaussian noise?
We can cool down our detector to create less noise. This is because when it is cold, the free charge cannot move as much
Why can't we use a very high voltage in capillary electrophoresis?
We can increase the velocity by increasing the voltage, but we can only go so high because: 1. Due to resistance, increasing the voltage generates heat which increases longitudinal diffusion, might denature proteins or alter chemical reactions
Why is it easier to do kinetics experiments with double-beam scanning spectrophotometers?
We can monitor absorbance as a function of time and if it takes you a long time to keep blanking, you will mess up the chemistry where the reactions are going on and you want to capture that. In addition, source intensity and detector response will slowly drift
Why can't we use OTC in HPLC?
We cannot use open tubular columns in LC because diffusion is 10^4 times slower in liquids than in gases. We use packed columns so the solute does not have to travel very far to encounter the stationary phase, which reduces C term!
Why is it easier to scan multiple wavelengths in double-beam scanning spectrophotometers?
We do not have to remove the samples to blank at each wavelength. Not only does it take time to re-measure blanks, but every time we move the cuvette it goes some error. Also, the more time it takes the more the temperature could change and the amount of light being put out also changes
Why is fiber optics useful in spectroscopy?
We do not want to be near the sample when we are measuring it because it might be dangerous
How do we determine V0 for SEC?
We need a really large protein that will not go through the pores
Why don't all molecules fluoresce or phosphoresce?
We need certain functional groups like pi electrons and electrons in nonbonding orbitals
With adsorption chromatography, if we want our analyte to come off of the stationary phase what do we do?
We use a stronger solvent to outcompete the analyte
How do we quantify Vm for SEC?
We use something really small that goes through like a radioactive ion or since it is the total volume of the column we can find the volume of the cylinder by πr^2L
Why do we use absorbance instead of transmittance?
We want a linear response so we can mathematically analyze it • log(1/T) • -log(T) • Then we can plot absorbance v. concentration and be linear
If we are using gradient elution in normal phase HPLC, how would we alter the solvent over time?
We would make it more polar as the experiment went on
What is laser pumping?
When electrons relax down to the ground energy level and emit a photon, energy is transferred from external source to tasing medium produce excited state atoms which give off light
When light is absorbed by a molecule, what happens to the beam?
When light is absorbed by a molecule, power of the beam decreases and we can quantify that . Energy per second per unit area of the beam decreases
Constructive interference occurs when?
When the difference in the path length is equal to the wavelength of light
What is constructive interference?
Where two waves arrive in step reinforcing one another (increasing the amplitude)
What is destructive interference?
Where two waves arrive out of step cancelling one another out
What is the difference in absorption atomic and absorption molecular spectroscopy?
Width of absorption bands...they are much narrower in atomic spectroscopy and there is little overlap between lines from different elements in the same sample. Instruments can measure up to 70 elements simultaneously
What are X-rays?
X-rays are high energy photons generated when high energy electrons are accelerated into an anode of certain material
Why is a CCD detector helpful in low light experiments?
You can add up the charge from the wells
Why does phosphorescence take longer than fluorescence?
You have to flip the spin of the electron going from T1 to S0
Why is fingerpicking not a great method for glucose monitoring in diabetics?
You will lose sensation in fingertips, bloody, insufficient sampling frequencies and you don't capture the hypo or hyperglycemic
Species A and Y do not absorb light. To facilitate their quantification, they are mixed with reagent C to form A-C and Y-C complexes that do absorb light. The molar absorptivity data for A-C and Y-C complexes at the respective absorption peaks are as follows: εA-C at 510: 42400 and at 656: 1,240 εY-C at 510: 2520 and at 656 23,500 A 5.00 mL water sample from a swimming pool was collected, mixed with 2.00 mL of reagent C, and diluted to a total volume of 20.0 mL with water. A 4.00 mL aliquot of this solution was then transferred into a cuvet (pathlength=1.00 cm), inserted into a spectrophotometer, and the absorbance measured at two wavelengths. At 510 nm, the absorbance of this solution was 0.667. At 656 nm, the absorbance of this solution was 0.447. Calculate the concentrations of A and Y in the pool water.
[A]=5.84 x 10^-5 M [Y]=7.61 x 10^-5 M
10 mL of pond water next to a paint company (metals probably in this pond water..cobalt and nickel) collected, mixed with 2 mL of a chemical to get them to absorb light and diluted to Vt=50.0 mL with H2O. A 4 mL aliquot transferred to a cuvet (b=1 cm) and measured in spectrophotometer at 510 nm (0.467). And 656 nm (0.347). Calculate the concentration of cobalt and nickel in solution. • ε co: 36,400 at 510 nm and 1240 at 656 nm • ε Ni: 5520 at 510 nm and 17500 at 656 nm
[Ni]: 9.56 x 10^-5 M [Co]: 4.96 x 10^-5 M
The molar absorptivities of compounds X and Y were measured with pure samples of each: At λ 272, εx=16400 and εy=3870 λ 327, εx=3990 and εy=6420 A mixture of X and Y in a 1 cm cell had an absorbance of 0.957 at 272 nm and 0.559 at 327 nm. Find the concentrations of X and Y in the mixture. Find the concentration of X if the absorbances are 0.700 at 272 nm and 0.500 at 327 nm.
[X]= 4.43 x 10^-5 M [Y]=5.95 x 10^-5 M [X]=2.63x10^-5
What is the refractive index?
a measure of how much rays of light are bent by a medium
What is UV-Vis absorption?
a molecule goes from ground state (S0) to excited state (S1)
In reverse phase chromatography, what type of solvent has a higher eluent strength?
a non polar solvent
With regards to energy, it is easier to think of light as what?
a particle
Each line on a grating acts was what?
a separate source of radiation
A 3.96 x 10-4 M solution of compound A exhibited an absorbance of 0.624 at 238 nm in a 1.000 cm cuvet. A blank solution containing only solvent had an absorbance of 0.029 at the same wavelength. a. Find the molar absorptivity of compound A. b. The absorbance of an unknown solution of compound A in the same solvent and cuvet was 0.375 at 238 nm. Find the concentration of A in the unknown. c. A concentrated solution of compound A in the same solvent was diluted from an initial volume of 2.00 mL to a final volume of 25.00 mL with water, and then measured to have an absorbance of 0.733. What is the concentration of A in the concentrated solution?
a. 1.5 x 10^3 M-1 cm-1 b. 2.3 x 10^-4 M c. 5.9 x 10^-3 M
Why is it important to measure absorbance at the maximum wavelength for a substance?
a. The sensitivity of the analysis is the greatest and so we will get the maximum response for the given concentration of analyte b. The curve is relatively flat at the maximum, so there is little variation in absrbance if the monochrometer drifts a little or if the width of the transmitted band changes slightly
In order for a molecule to fluoresce, what must it be able to do?
absorb light!
What is Beer's Law?
absorbance is proportional to concentration
What is the Beer-Lambert Law?
absorbance is proportional to path length or concentration
How do we decrease chemical interference?
add releasing agents (EDTA, 8-hydroxyquinoline), higher flame temperatures,
What is the adjusted retention time?
additional time required to travel the length of the column beyond that required by solvent (tm). The solvent is unretained and travels through the column the fastest
An excitation spectrum looks a lot like what type of spectrum?
adsorption
When is ionization interference a problem?
alkali metals at low temperatures and other elements at higher temperature
Why is it nice to have optical fibers carry light by total internal reflectance?
almost all rays entering one end of the fiber within a certain range will energy from the other end of the fiber with little loss
What are the most common type of electrochemical detectors?
amperometric
What type of detector is used in the NO-releasing GOx-based biosensor?
amperometric
What is the Doppler effect?
an atom moving toward the radiation source experiences more oscillations of the EM wave in a given time period than one moving away from the source. Atom moving towards the source absorbs lower frequency light than one moving away
What happens in an electronic transition?
an electron from one molecular orbital moves to another molecular orbital with an increase or decrease in energy of the molecule
What is atomic absorption often used for?
analysis of metals
What is gas-solid adsorption chromatography?
analyte is adsorbed onto the solid particles of the stationary phase
What is interference?
any effect that changes the signal while the analyze concentration remains unchanged
What is 1 plate height equivalent to?
approximately the length of the column required for 1 equilibration of solute between mobile and stationary phases
What type of solvent is better for an extraction with charged species?
aqueous
What are applications of XRF?
art and archeology
When does shot noise dominate?
at small currents/small #s of photons
In what type of atomic spectroscopy is a hollow cathode lamp used?
atomic absorption
How does a photodiode detector work?
b. Rows of p-type silicon on a substrate of n-type silicon create a series of pn junction diodes c. A voltage is applied to each diode and electrons and holes are drawn away from the junction d. In the depletion region in each junction there are few electrons and few holes e. The junction acts as a capacitor, with charge stored on either side of the depleted region. f. When radiation strikes the semiconductor, free electrons and holes are created and migrate to regions of opposite charge, partially discharging the capacitor g. The more radiation that strikes each diode, the less charge remains at the end of the measurement h. The state of each capacitor is determined at the end of each cycle by measuring the current needed to recharge the capacitor
How are stationary phases chosen?
based on like dissolves like
How does resolution relate to groove spacing?
better resolution with smaller groove spacing
For molecular exclusion chromatography, what is the K value for intermediate sized molecules?
between 0 and 1
What do we do with X rays?
blow things up
What do we do with cosmic rays?
blow things up
What do we do with gamma rays?
blow things up
Capillary electrophoresis is typically carried out in what?
buffer soaked paper or gel
Conductometric detectors measure what type of property?
bulk
In gas chromatography, how is the analyze transported through the column?
by a gaseous mobile phase (carrier gas)
A PMT can be used for which of the following: a) Recording an entire spectrum at once b) Measuring a molecule's vibrational mode c) Measuring a few photons of light d) All of the above e) None of the above
c) Measuring a few photons of light
Fluorescence lifetimes are shorter than phosphorescence life times because: a) S1 to S0 are greater in energy than T1 to S0 b) S0 to T1 transitions are spin forbidden c) T1 to S0 spin transitions require change in spin quantum number d) The T1 state is really stable compared to S1
c) T1 to S0 spin transitions require change in spin quantum number
What are the types of capillary electrophoresis?
capillary zone electrophoresis and micellar electrokinetic capillary electrophoresis and capillary electrochromatography and capillary gel electrophoresis
What is the order of elution in capillary zone electrophoresis?
cations, neutral, anions
What is chemical interference?
caused by any component of the sample that decreases the extent of atomization of an analyte
In affinity chromatography, how do we get the solute to come off of the column?
change pH, add surfactant, change the ionic strength of the solution
Electrophoretic mobility is proportional to what?
charge
What does CCD stand for?
charge coupled device
How do you deal with overlap between lines of different elements in a samoke>
choose another wavelength for analysis or use a high resolution spectrometer because they eliminate interference from other elements by resolving closely spaced lines
What leads to premature death in CF patients?
chronic infection and respiratory failure
What is a wavenumber?
cm^-1
What is pressure broadening?
collisions between atoms. Collisions shorten the lifetime of the excited state
What is the most simple filter?
colored glass
Absorbance is directly proportional to what?
concentration
What is detection limit?
concentration of analyte that gives 3:1 signal to noise ratio
What is molar absorptivity?
constant for a compound at a given frequency (v) or wavelength (λ)
What is electrophoretic mobility?
constant of proportionality between the speed of the ion and electric field strength
What type of interference do we have with normal light waves?
constructive and destructive interference. The light waves are diverged and dispersed
X-rays eject what?
core electrons
What is the current idea of how to deal with NO precursor leeching?
covalently attach the NO donor to the polymer backbone
In a photodiode array detector, radiation intensity is proportional to what?
current
What is a hertz?
cycles/second (complete oscillations a wave makes in 1 second
The sensitivity of a photomultiplier tube is limited by what?
dark current
Why do we need a response factor?
detectors typically have different responses to different components
How does dispersion relate to groove spacing?
dispersion increases with decreasing groove spacing
What type of spectrophotometer is a beam chopper used in?
double-beam scanning
How does a deuterium arc lamp work?
electric discharge caused D2 to emit UV radiation
What drives separation in capillary electrophoresis?
electric field
More analytical methods are based on what than anything else?
electrochemistry
What is absorption?
electromagnetic (light) energy is transferred to atoms, ions, or molecules in the sample. The transition can be a change in electronic levels, vibrations, rotations, translation, etc. Due to the light, the molecule goes from ground state to an excited state
What types of analytes can the ECD be used for?
electron capturing solutes
Vibrational levels exist between what?
electronic levels
What is the Franck Condon Principle?
electronic transitions are so fast relative to nuclear motion that each atoms has nearly the same postion and momentum before and after a transition
In capillary electrochromatography, what is the mobile phase driven by?
electroosmosis
How do we shield to minimize noise?
eliminate environmental noise by blocking all external electrical fields
What do high resolution spectrometers do?
eliminate interference from other elements by resolving closely spaced lines
What is luminescence?
emission of light from an excited state of a molecule
What is phosphorescence?
emission of radiation (photon) from T1 to S0 (between states with different spin)
What is X-ray fluorescence?
emission of x-rays following the absorption of x rays by a material
LASER controls how species do what?
emit photons
Heated objects glow and do what?
emit radiation
What are the components of a grating monochrometer?
entrance and exit slits, mirrors, and a grating
What gives rise to separation in chromatography?
equilibrium of the solutes between the 2 phases
Fluorescence is going from what state to what state?
excited state to ground state
Phosphorescence is going from what state to what state?
excited state to ground state
If increasing the number of grooves in a grating increases resoltuion, why don't we use the greatest number of grooves possible?
expensive
What is noise?
extraneous electron signal
T/F: Alcohol affect pregnancy tests
false
T/F: Basal levels of hCG can trigger false positives
false
T/F: Birth control pills affect pregnancy tests
false
T/F: Drugs affect pregnancy tests
false
T/F: Longer reading times enhance pregnancy test sensitivity
false
T/F: Smoking will affect pregnancy tests
false
T/F: stress affect pregnancy tests
false
A tungsten arc lamp is a source used to collect spectra in the UV region, true or false?
false (visible and near IR)
Polyethylene cuvets can be used for what wavelength range?
far IR
T/F: Blood pregnancy tests are more sensitive
fasle
How is the problem of porous silica beads fixed?
faux porous shell around a solid bead...you still end up with a relatively large surface area, but the analytes cannot go all of the way in.
What is a solid stationary phase in GC?
fine solid particles packed into stainless steel tubing; carbon (carbon black), SiO2 (silica gel), Al2O3 (alumina) and the analyte adsorbs directly on solid particles
What is an aerosol?
fine suspension of liquid or solid particles in a gas
What is the existing technology for glucose monitoring in diabetics?
fingerpricking
In atomic absorption, what replaces the cuvet of conventional spectroscopy?
flame
Does a flame or furnace require more sample?
flame, it is less sensitive
How is atomization achieved in atomic spectroscopy?
flames, furnaces, or plasma
Is fluorescence or phosphorescence faster>
fluorescence
What are examples of luminescence?
fluorescence and phosphorescense
What type of atomic spectroscopy is more sensitive?
fluorescent
We refer to microwaves by what?
frequency
We refer to radio waves by what?
frequency
Electrophoretic mobility is inversely proportional to what>
friction
How is the concentration determined in atomic absorption?
from calibration curves or an internal standard and it is proportional to absorption
Whaat type of atomizer is more sensitive and why?
furnaces because in flames the analyte spends less than 1 second in the optical path, so 1-2 mL are needed whereas in furnaces the analyte spends several seconds so only 1 ul is needed
In an open tubular column, what are the walls made from?
fused silica
What type of cuvets are used for UV spectroscopy?
fused silica
What type of cuvets are used for visible spectroscopy?
fused silica or glass
In partition chromatography, what is the mobile phase?
gas
What are the 2 types of gas chromatography?
gas-liquid partition chromatography and gas-solid adsorption chromatography
What is the mobile phase in gas chromatography?
gaseous (He, N2 or H2)...as long as the mobile phase is inert and will not react with the solute the choice is not criticle
What does LH stimulate the corpus luteum to do?
generate progesterone
What are the sources of IR light?
globar, NiChrome, Nernst glower
What is a furnace made of?
graphite
In a grating monochrometer, what disperses the light?
grating
Greater dispersion results in whaat?
greater angle separating 2 closely spaced wavelengths
Higher k' means what?
greater solute retention
Absorption is going from what state to what state?
ground state to excited state
How do the sources of infrared light work?
heater elements through which a current is passed
What does HETP stand for?
height equivalent to a theoretical plate
In HPLC, what is the mobile phase driven by?
high pressure
As a graduate student, I used an Argon ion laser that put out 514 nm green light. Is this light a higher or lower energy than a Ti-Sapphire laser operating at 720 nm?
higher
Compared to absorption wavelength, what is emission wavelength like?
higher
Pros of an OTC?
higher resolution, shorter analysis times, greater sensitivity compared to packed columns
What is polarized light?
highly directional light that propagates along a single axis. Light propagates along the x acid, the electric field oscillates in the xy plane and the magnetic field oscillators in the xz plane
What do we use for the light source for absorption atomic spectroscopy?
hollow cathode lamp
What is the setup to measure atomic absorption?
hollow cathode lamp --> flame/furnace --> monochrometer --> detector Sample is injected into a nebulizer just below the flame/furnace
In the 1920s, how was pregnancy determined?
hormone testing in lab
What is an optical window in a furnace?
how light enters
Circle which of the following correctly depicts the proper order of energies from low to high for the following electromagnetic radiation: i. Microwave, Vis, X-ray, UV ii. Radio, Microwave, Vis, UV iii. IR, Microwave, UV. Vis iv. Microwave, IR, UV, Vis v. None of the above.
ii. Radio, Microwave, Vis, UV
What happens if the egg is fertilized?
implantation of fertilized egg and trophoblast cells secrete Human Chorionic Gonadotropin (hCG) to continue stimulation of Corpus Luteal Progesterone Production
In unpolarized light, how do electric fields travel?
in all directions
In unpolarized light, how do magnetic fields travel?
in all directions
In unpolarized light, how does light propagate?
in all directions
What is charring?
in furnaces, it destroys organic matter and creates smoke that would interfere with the determination of concentration
In polarized light, the magnetic field oscillates how?
in the xz plane
What is the general elution problem?
inability of a single isothermal separation to provide adequate separation within a reasonable run time for samples containing compounds of widely different boiling points
How can we decrease longitudinal diffusion of our solute?
increase velocity
In continuous glucose monitors, why is increasing the lifetime better?
increased compliance
If all of the light is absorbed, what is absorbance?
infinite
What type of light does NiChrome wire give off?
infrared
What type of light does a Globar give off?
infrared
What type of light does a Nernst glower give off?
infrared
In microporous silica, where is the majority of the surface area?
inside the pores
What does temporal coherence allow for?
it allows for a very narrow spectrum to emit pulses of light
What does spatial coherence allow for?
it allows for tight focusing of lasers light, and it keeps beams collimated (parallel) over long distances
Why can't we amplify a signal to get rid of noise?
it also amplifies the noise
What happens when we shine light on a grating?
it causes different wavelengths to diffract at different angles
What happens to the refractive index of the mobile phase as a solute passes through it?
it changes the entire refractive index of the solvent
What does a nebulizer do?
it creates a an aerosol (fine suspension of liquid or solid particles in a gas) from aa liquid sample
How does the level of hCG change during pregnancy?
it doubles every 2-3 days until 8 weeks
How does noise increase with number of experiments?
it increases by n^1/2
How does pulse width change with time after pacemaker implant? Why?
it increases hugely because scar tissue forms due to the foreign body response and scar tissue is not excitable, and it decreases electrical stimulation efficiency, so we need a longer pulse width
When a molecule or atom absorbs light, what happens to it?
it increases in energy. And when you absorb energy, it can cause the ground state molecule to be excited
How does signal increase with the number of experiments?
it increases linearly
In a grating monochrometer, what does a smaller slit do?
it increases resolution, but it decreases the amount of light reaching the detector
Why is increasing the surface area of the stationary phase a good thing?
it increases the amount of solute that can be loaded without overloading the column and the more surface area the better the separation
Why is gold good to coat pacepakers with?
it is anti-inflammatory
When light is absorbed by a sample, what happens to the irradiance of a beam?
it is decreased
Can gradient elution be used with liquid-liquid chromatography?
it is difficult
What causes shot noise?
it is due to the quantized nature of carriers and photons
How does a Globar light source work?
it is heated by an electric current
What is important about the cuvets used in spectrophotometry?
it is important that they do not absorb any light
How does Johnson/Gaussian noise change with frequency?
it is independent of frequency
How does shot noise change with frequency?
it is not frequency dependent
Downside of a phototube detector?
it is not the most sensitive
What is IR absorption not used for and why?
it is not used to quantify because it is not sensitive enough and there are too many peaks.
In emission atomic spectroscopy, how do we determine the concentration of element in the sample?
it is proportional to the emission intensity
What is the direction of Johnson/Gaussian noise?
it is random in direction, both positive and negative
What is spiking?
it is used to identify a peak; it compares a certain peak's retention time with that of an authentic sample of the suspected compound. The authentic compound is added to the unknown. If the authentic compound and the unknown are the same, the relative area of one peak will increase
What is lock-in amplification?
it is used to minimize noise and we produce an analytical signal in phase with the detector away from the noise
Why is baseline drift a bad thing?
it makes quantification and determination of resolution very difficult
What does a large partition coefficient mean in an extraction?
it means that less solute remains in phase 1
For a molecule to be analyzed by spectrophotometry, what must be true?
it must absorb light and its absorbance must be distinguishable from any absorbance due to other substances in the sample
In polarized light, how does light travel?
it propagates along a single axis, the x-axis
The first mirror of a laser does what?
it reflects all photons
What does mirror 2 do in a laser?
it reflects most photons
What is drying?
it removes water from the sample
What is the downside of a furnace?
it requires more operators skill
What does it mean if a detector is sensitive?
it responds to a low amount of solute
What is a grating monochrometer?
it uses diffraction to bend light and separate it out by wavelength
How does a prism work to select wavelengths?
it uses refraction to ben light and separate it out by wavelength. Refractive index varies with wavelength causing different colored light to refract differently and leave the prism at different angles.
With the Pt(Ir)/Au-C12SH modified pacemaker electrode, what was the pulse width like?
it was very good and there was no huge rise in the acute phase and the chronic phase is pretty close to the initial implant state
The fluorescence emission spectrum of a molecule occurs at higher wavelengths than the molecule's absorbance spectrum because: i. Beer-Lambert law ii. Franck-Condon principle iii. Jablonski effect iv. Vibrational relaxation
iv. Vibrational relaxation
What do we use for the light source in fluorescence atomic spectroscopy?
laser
What does laser stand for?
light amplification by stimulated emission of radiation
What is transmission?
light enters the cuvette and then comes back out
In ion-exchange chromatography, what is the mobile phase?
liquid
What type of samples can a flame atomize?
liquid
What are the types of chromatography in HPLC?
liquid-liquid partition and liquid-solid adsorption
Molecules emit radiation at a _____________ wavelength than what they absorb
longer
In continuous glucose monitors, longer NO release leads to what?
longer accurate lifetime
What is the B term in the Van Deemter equation?
longitudinal diffusion
What is the only source of peak broadening in capillary electrophoresis?
longitudinal diffusion
Below the optimal linear velocity, what is the greatest thing that affects plate height?
longitudinal diffusion broadening
What is a solute property detector?
look at a specific property of an analyte
What types of wavelengths do flames give off?
lots of different ones
Compared to the absorption energy, what is the emission energy?
lower
what is m/z?
mass to charge ratio in ICPMS
Above the optimal linear velocity, what is the greatest thing that affects plate height?
mass transfer
What is the C term in the Van Deemter equation?
mass transfer
Raman spectroscopy was used to do what?
measure the structure of the interface
Minimum energy light needed to cause rotational excitations?
microwave
What is electrophoresis?
migration of ions under the influence of electric field
Microwaves can cause molecules to do what?
molecular rotations
What does molecular size exclusion separate based on?
molecular size
Infrared light can cause molecules to do what?
molecular vibrations
What are the disadvantages of lasers?
monochromatic, expensive, high maintenance
What type of wavelengths do lasers provide?
monochromatic; 1 wavelength
Filters must be used in conjunction with what?
monochrometer
In a photomultiplier tube, each time an electron hits a dynode what happens?
more electrons are formed
In a photomultiplier tube, the voltage on subsequent dynodes is
more positive
How long does phosphorescence take?
more than 10^-6 seconds
What type of wavelengths do normal light waves provide?
multiple
Why is the speed of light less in air?
n (refractive index) is greater than 1 and therefore light bends a bit in air (c/n)
What type of emission lines does aa hollow cathode lamp provide?
narrow...monochromatic
Whaat type of ions move towards the anode?
negative
What is the charge of a cathode?
negative
Are all light sources blackbody radiators?
no
Can gradient elution be used with size exclusion chromatography?
no
Do molecules have the same spectra as atoms?
no
What type of lamp is needed in emission atomic spectroscopy?
no lamp
What is an open tubular column?
no packed stationary phase
Is the electron capture detector destructive or non destructive?
non
In normal phase HPLC, which molecules come off of the column first?
non polar and then less polar
In reverse phase HPLC, what types of molecules are separated?
non polar molecules are separated from other non polar
What is a liquid stationary phase in GC?
non-volatile liquid coated on inside of column or on fine solid support
Is the thermal conductivity detector destructive or not?
not
How sensitive is the thermal conductivity detector?
not very
Radio waves can cause molecules to do what?
nuclear spin
Most common gas chromatography column:
open tubular
What are the 2 types of columns that can be used in chromatography?
open tubular or packed
What type of solvent is better for an extraction with neutral species?
organic
What is a flame ionization detector (FID)?
organic solutes are burned in H2 and hot air producing CH radicals and eventually CHO+. CHO+ ions are collected by a cathode and produces a current as the response. Ion production is proportional to the number of susceptible carbon atoms entering the flame
What types of analytes can flame ionization detectors be used for?
organics (reduced carbons only)
What is dark current?
output of detector in the absence of light. Background signal
What are the limitations of using silica as a stationary phase support?
pH > 8-9 silica starts dissolving and pH < 2 starts hydrolyzing (bonded stationary phase lost)
What is the pH of a 1.05 x 10^-8 M solution of NaOH
pH=7.02
In HPLC, what type of column is used?
packed
In adsorption chromatography, what type of column is used?
packed
What does collimated mean?
parallel and non-diverging
Which type of chromatography is most like extraction?
partition
What is a light wave?
perpendicular oscillating electric and magnetic field
What is the energy like between fluorescence and phosphorescence?
phosphorescence energy is less
What are the wavelength differences between fluorescence and phosphorescence?
phosphorescence wavelength is larger because it is less energy
A grating polychrometer is used only in what type of detector?
photodiode array
What does PMT stand for?
photomultiplier tube
What is the most common source of atoms in atomic emission spectroscopy?
plasma
What type of solvent is acetonitrile?
polar
What type of solvent is methanol?
polar
In normal phase HPLC, what type of molecules are separated?
polar molecules are separated from other polar molecules
In normal phase chromatography, what type of solvent has a higher eluent strength?
polar solvent
In reverse phase HPLC, what molecules come off of the column first?
polar, then less non polar
What is capillary gel electrophoresis?
polymer network (gel) that entangles larger molecules to a greater extent
What is absolutely necessary for lasing?
population inversion
What is the charge of an anode?
positive
What type of ions move towards the cathode?
positive
What are HPLC grade solvents?
pre-filtered w/ 0.2 micron filter, extends pump life, reduces column plugging because column plugging can be caused by any particulate in the solvent because the pores in the column are very small, degassed prior to use
What is the most basic wavelength selector?
prism
What is intersystem crossing?
radiationless transition between states with different spin quantum numbers (S1 to T1)
What is the direction of shot noise?
random in direction; positive or negative
What is dynamic range?
range over which detector responds in any manner to changes in analyte concentration
What is a He-Ne laser a common source of?
red light
What is the surface of a grating like?
reflective!
How can interference be corrected?
remove the source or by preparing standards that exhibit the same interference
How can we get different wavelengths of light to pass through the exit slit of a grating monochrometer?
rotate the grating
What is a fluorescence detector?
sensitive to naturally fluorescent analyses or to fluorescent derivatives
What is inductively coupled plasma mass spectrometry used for?
separates components based on their mass to charge ratio
What is affinity chromatography?
separation based on antibody-antigen or enzyme-substrate interactions.
What is size-exclusion/gel permeation chromatography?
separation based on molecular size
What is adsorption chromatography?
separation based on solute adsorption on surface of stationary phase. Stationary phase has discrete binding places. The analyte can chemically interact with the stationary phase and stick to it and the solvent is competing with analyte for the binding spots on the stationary phase
What is partition chromatography?
separation based on solute dissolving into stationary liquid. The stationary liquid is bound to the silica stationary phase support. Instead of binding to the stationary phase, the solute equilibrates between the mobile and liquid stationary phases and based on the polarity of the phases, the solute will spend more time in 1 phase compared to another
What is micellar electrokinetic capillary electrophoresis?
separation of neutral molecules via partitioning, and so the longer the molecule spends inside of the micelle, the longer its migration time. There is a psuedo stationary phaase so C is not 0
How many detectors do each LC have?
several
What is the residence time in a furnace?
several seconds
How was pregnancy determined in medieval times?
sight and smell
The capillaries used in conventional capillary electrophoresis are made of glass and their inner surface bears an immobile negative charge. To what is this charge due and what is its consequence in CE experiments?
silanol (SiOH) and electroosmosis
What are Is-based photodiode arrays?
silicon doped with chemicals that have either more or less electrons than Silicon
What is capillary electrochromatography?
similar to HPLC except mobile phase driven by electroosmosis (not high pressure)
What are the 2 different electronic states that can arise from an electronic n --> π transition?
singlet state or triplet state
If a compound doesn't absorb much light, what is the value of molar absorptivity going to be like?
small
In capillary gel electrophoresis, which molecules travel the fastest?
smaller
The greater the resolution,
smaller difference between two wavelengths that can be distinguished from each other
Why are columns coiled in the oven?
so a greater length can fit because greater length means greater resolution
Why do we need the defects between the R groups on the pacemaker surface?
so electrons can go in and out and we can maintain electrical conductivity
Whaat type of sample can a furnace atomize?
solid or liquid
What is porous layer open tubular column?
solid stationary particles on the inside wall of a column
Amperometric detectors measure what type of property?
solute
Potentiometric detectors measure what type of property?
solute
UV-Vis spectroscopy detectors measure what type of property?
solute properties
Electrophoresis is what type of property?
solute property
Relate the magnitude of spacings between vibrational levels to those between rotational levels?
spacings between rotational levels are smaller than vibrational levels
What is the plural of spectrum?
spectra
What are the types of interference?
spectral, chemical, ionization, isobaric
What does environmental/line noise look like on a spectrum?
spikes over the spectrum at 60 Hz and multiples thereof
What happens to MAHMA in water
stable except with water Water protonates the nitrogen and liberates the NO
In GC, what happens as the column ages?
stationary phase can be lost, surface silanol groups are exposed and tailing can increase
What is the stationary phase in molecular size exclusion?
stationary phase is a cross linked polymer or cross linked gel of controlled pore size
What is gas-liquid partition chromatography?
stationary phase is a non volatile liquid bonded to the inside of the column or to a solid support
What does progesterone do?
stimulates enrichment of uterine lining
Ideal characteristics of a solid support for a liquid stationary phase in GC?
strong, porous, high surface area and inert (non-adsorptive)
What are 2 mechanisms that broaden line width?
the Doppler effect and pressure broadening
Fluorescence intensity measures what?
the absolute number of photons
What determines how truly monochromatic a laser is?
the bandwidth of the laser, therefore we still use a monochrometer
What is diffraction?
the bending of light rays by a grating
What is refraction?
the bending of light rays by a prism or lens
Why do double-beam scanning spectrophotometers reduce source and detector drift?
the blank and sample are compared so frequently
What is a signal?
the chemically relevant electron signal
What is wavelength?
the crest to crest distance between waves
What is unpolarized light?
the electric and magnetic field components go in all directions
What is fluorescence?
the emission of radiation (photon) from excited state to ground state with the same spin
What is 1/f noise caused by?
the flickering or drifting of light source by the slow changes in instrument component with temperature and/or age or the variation in the power line voltage to an instrument
What is an eluate?
the fluid emerging from the bottom of the column
How does nitric oxide affect CF sputum?
the greater the dose, the less viscous the mucus is
What does a large relative retention mean?
the greater the separation between 2 solutes (k2/k1)
How does 1/f noise change with frequency?
the higher the frequency, the lower the noise
What are the first molecules to elute in molecular exclusion chromotography?
the larger molecules that cannot fit into pores
The higher the diffraction order, what happens?
the less intense the light
The higher the wavelength, what does this mean about energy?
the lower the energy
What state do most molecules want to be in?
the lowest energy state
What level is the level from which light emission happens?
the lowest vibrational level
What does a negative electrophoretic mobility mean?
the molecule is migrating in the opposite direction from the electroosmotic flow
In reverse phase HPLC, which molecules come off of the column last?
the most nonpolar
What is spectral interference?
the overlap of analyte signal with signals due to other elements or molecules in the sample or due to the flame or furnace
Why does HPLC give good resolution?
the particles are very fine
The current in a phototube detector is proportional to what?
the radiation intensity
Hollow cathode lamps contain a vapor of what?
the same element that is being analyzed
What is a singlet state?
the spins of the electrons are opposed
What is a triplet state?
the spins of the electrons are parallel
What removes the friction between the solvent and the walls of the capillary in capillary electrophoresis?
the surface charges
What is retention time?
the time that elapses between injection and arrival of that component to the detector?
In GC, what is the principle determinant of retention?
the volatility of the solutes
What is retention volume?
the volume of mobile phase required to elute a particular solute
What is Vm-Vo in SEC?
the volume of solvent inside of the gel
What do slits do in grating monochrometers?
they allow only the wavelength of light through that we want to use in the experiment
When light is reflected, what is the angle of incidence and what is the angle of reflection?
they are equal
What happens when adjacent light rays are out of phase?
they cancel each other out
Overall, what do detectors do?
they convert the light that has been transmitted through the sample into an electrical signal
What are molecular orbitals?
they describe the distribution of electrons in a molecule
As the thickness of the stationary phase goes up, what happens to retention times?
they increase
What type of lines do lasers provide?
they provide isolated lines of a single wavelength (monochromatic)
What happens when adjacent rays are in phase?
they reinforce each other
Why is a large surface area in chromatography a good thing?
this means more stationary phase which means better separation
Where is the sample injected in furnace?
through a hole at the center
What is the retention factor/capacity factor?
time solute spends in stationary phase/time solute spends in mobile phase
Why do molecules vibrate?
to give off energy
What does biocompatible mean?
to make surer the body doesn't have a foreign body response
How is light carried through optical fibers?
total internal reflectance
Absorption results from what?
transition to a higher energy state
What produces Human Chorionic Gonadotropin?
trophoblast cells in placenta during pregnancy
IR spectroscopy can be used to distinguish the functional group of a molecule, true of false?
true
A normal light bulb is similar to what kind of lamp?
tungsten lamp
What type of liquids are used in solvent extractions?
two immiscible liquids (usually aqueous/organic solvent combos)
Gamma rays can cause molecules to do what?
undergo nuclear transitions
What are the units of molar absorptivity?
units of L mol-1 cm-1
What types of analytes can a thermal conductivity detector be used for?
universal; responds to all analytes
If we are interested in a molecule that doesn't fluoresce or phosphoresce, what can we do?
use a label!
What are packed GC columns used for?
used for preparative separations or to separate gases that are poorly retained
How can 1/f noise be detected?
using standards to measure and then correcting the instrument
UV rays can cause molecules to do what?
valence electrons to move
Visible light can cause molecules to do what?
valence electrons to move
What are important factors to consider before temperature programming?
variations in solubility, changes in volatility, solute stability problems, flow rate changes, stationary phase stability
What type of stationary phase is silica?
very polar
When aa molecule absorbs enough light to undergo an electronic transition, what else happens?
vibrational and rotational transition
What is non radiative transition?
vibrational energy is usually transferred to other molecules through collisions, not by photon emission. The net effect is converting part of the energy of the absorbed photon into heat spread throughout the entire medium
Glass cuvets can be used for what wavelength range?
visible
What type of light does a tungsten lamp give off?
visible and near-IR
What type of light is typically used in spectrophotometry and why?
visible because most compounds absorb UV radiation, so it cannot be used to tell one from another
Glass cuvets can be used for what?
visible wavelength ranges
What is pulse width?
voltage pulse time period necessary to cause heart beat
What is stray light?
wavelengths outside of the bandwidth expected from the monochrometer
We refer to infrared light in terms of what?
wavenumbers
We can describe light in terms of whaat?
waves and particles
How do we filter to minimize noise?
we block out all electrical responses in other frequency ranges
When doing an extraction, the solute is most soluble in whaat type of solvent?
whatever solvent has a polarity similar to the solute's
In HPLC, what is elution?
when solvent displaces solute from the stationary phase
What is isobaric interference?
when the interfering ion has the same mass to charge ratio as the analyte ion
Which of the following types of noise is independent on frequency: drift, white, pink, environmental?
white
Ideal characteristics of liquid stationary phase in GC?
wide liquid range (min/max temp limits), stable, low volatility, low viscosity (↑D and ↓RMT)
What is the difference between emission atomic and emission molecular spectroscopy?
width of emission bands
In an OTC, where does solute interact?
with the walls of the column
Are flame ionization detectors destructive or not?
yes
Can gradient elution be used with adsorption chromatography?
yes
Can gradient elution be used with bonded phase chromatography?
yes
Can gradient elution be used with ion-exchange chromatography?
yes
How can you change the wavelength of light that passes through a prism slit?
you can change the position of the prism
Which subunit of hCG maintains some activity alone?
β
What is the incident angle?
θ; always positive
Convert 105 MHz to wavelength.
λ=2.86 m
What is the reflection angle?
φ
How does the electron capture detector work (ECD)?
• Gas entering the detector is ionized by high energy electrons (beta particles) emitted from a foil containing radioactive nickel. • Electrons in the plasma formed are attracted to an anode, producing a small current that is maintained at a constant level by variable frequency pulses applied between the cathode and anode • When analytes with a high electron affinity enter the detector, they capture some of the electrons and decrease the conductivity of the plasma and the detector responds by vaarying the frequency of voltage pulses to maintain a constant current • The frequency of pulses is the detector signal
How does a thermal conductivity detector work?
• The carrier gas must have a different thermal conductivity than the analytes. He is often used because it has a really high thermal conductivity. When the analyte emerges, the conductivity of the gas stream decreases, the filament gets hotter, the electrical resistance increases and the voltage across the filament changes. The detector measures this change in voltage. • The thermal conductivity of the elute is measured relative to that of the pure carrier gas
How does a He-Ne laser work?
• We use electricity to excite helium • Helium in the excited state transfers its energy to neon • Neon in E2 and gives off red light
How much is a pregnancy test?
$12
If a given sample absorbs no light, what is absorbance?
0
If all of the light is absorbed, what is % transmittance?
0
In molecular size exclusion, what is the partition coefficient if the polymer is too large?
0
What is the average of Johnson noise?
0
What is the percent transmittance of the first mirror of a laser?
0 %T
Theoretically, what are the range of Kav values in SEC?
0 to 1
Transmittance ranges from what to what?
0 to 1
If we are making absorption measurements, how many wavelength selectors do we have?
1
What is residence time in a flame?
1 second
What is the percent transmittance of the 2nd mirror in a laser?
1%
In analyzing a spectrophotometric mixture, there are 2 different situations to be considered in how to go about the analysis. What are they?
1) The individual spectra overlap 2) The individual spectra are well resolved
The partition coefficient of a weak acid HA (Ka=1.44 x 10^-5) between toluene and water is 650. 1. Calculate the formal concentration of HA in the aqueous phase after extracting 75 mL aqueous solution of 0.05 M HA with 25 mL of toluene at pH 2.8 2. Is the extraction of the acid into toluene more or less efficient at pH of 7? Why?
1. 2. Less! q=0.401, more left in water
1. If the signal from a photomultiplier tube during a fluorescence experiment is 4.00 microamps and the noise of this tube is 1.20 microamps, what would the signal-to-noise ratio be if 10 measurements were averaged. 2. Calculate the minimum number of spectra that must be averaged to obtain a S/N ratio of 15?
1. 10.5 2. 21
If we need to resolve lines that are 0.05 nm apart at a wavelength of 500 nm: 1. What is the required resolution? 2. If we want a first order resolution, how many grooves do we need? 3. If the grating has a ruled length of 10 cm, how many grooves/cm?
1. 10^4 2. 10^4 3. 10^3
1. Pure hexane has negligible UV absorbance above a wavelength of 200 nm. A solution prepared by disoslving 25.8 mg of benzene (C6H6, FM 78.11) in hexane and diluting to 250 mL had an absorption peak at 256 nm with an absorbance of 0.266 in a 1-cm cell. Find molar absorptivity of benzene at this wavelength 2. A saample of hexane contaminated with benzene had an absorbance of 0.070 at 256 nm in a cuvet with 5 cm pathlength. Find the concentration of benzene
1. 201 M-1 cm-1 2. 5.4 mg/L
A molecule with MW=100,000 elutes from a molecular exclusion column in a volume of 28.2 mL. The column has a diameter of 1 cm and a length of 100 cm. It is packed with a gel that has a fractionation range from MW 3,000 to 30,000. 1. At what retention volume would a compound with MW 750 elute? 2. At what retention volume would a compound with MW 45,000 elute? 3. At what retention volume would a compound with Kav=0.6 elute? 4. What is Kav for a molecule with MW of 500? 5. What is Kav for a molecule with MW of 60,000?
1. 78.54 mL 2. 28.2 mL 3. 58.40 mL 4. 1 5. 0
What is the advantage of photodiode arrays?
1. Different wavelengths reach different parts of the detector array, and all wavelengths are recorded simultaneously 2. Each diode receives a different wavelength 3. no need to select a single wavelength for analysis
Why is nitric oxide useful as an antimicrobial agent?
1. Endogenously produced 2. short half life 3. rapid diffusion (it can get through biofilms) 4. uncharged, so can get through biofilms 5. broad spectrum 6. bactericidal, not just inhibiting growth 7. Has multiple killing mechanisms
How to minimize noise?
1. Filter 2. Shield 3. Lock-in amplification 4. Signal averaging
What were the problems of coating sensors with NO?
1. How do we store and release it in a chemical form since it is a gas? 2. We want water to be taken up by the polymer and protonate the nitrogen and kick off the NO and the NO can diffuse out. It is zwitterrrionic, and therefore does NOT want to be in the organic polymer! It wants to be in solution, so we have leaking of the molecule and it is potentially toxic
What are the advantages of optical fibers?
1. Immune to electrical noise 2. Transmit data at a higher rate 3. little loss in light 4. handle more signal
What is the problem with commercially available pacemakers?
1. Inflammation 2. Scar tissue formation
An S1 molecule can do 3 different things. What are they?
1. Internal conversion: enter a highly excited vibrational level of S0 having the same energy as S1, and from here it can relax back down to the ground vibrational state and transfer its energy to neighboring molecules through collision 2. Intersystem crossing: cross from S1 to an excited vibrational level of T1 3. Fluorescence: relax from S1 to S0 by emitting a photon
What are the advantages of double-beam scanning spectrophotometers?
1. It is easy to scan multiple wavelengths 2. We can do kinetics experiments 3. Reduced source and detector drift
Why is Vancomycin not ideal?
1. It is hard to make 2. Not broad spectrum 3. Inhibits growth, does not kill 4. 1 killing mechanism
What are the 4 main sources of noise?
1. Johnson/Gaussian Noise 2. Shot Noise 3. 1/f or drift or pink noise 4. Environmental noise/line noise
How do we analyze a mixture when the individual spectra are well resolved?
1. Measure the absorbance at λmax for X and for Y 2.Solve: A'=ε'xb[X]+ ε'yb[Y] and A''=ε''xb[X]+ ε''yb[Y]
How do we analyze a mixture when the individual spectra overlap?
1. Measure the absorbance of each standard with known concentration at many wavelengths 2. Then, plot Am/Axs =[Y]/[Y]s *(AYs/AXs )+[X]/[X]s 3. We can find [Y] from the slope and [X] from the y-intercept
Why are OTC pregnancy tests important?
1. Over 6 million annual conceptions 2. privacy 3. early detection
How does a charge-coupled device (CCD) work?
1. P-doped Si on an n-doped substrate that is capped with an insulating layer of SiO2, on top of which is a pattern of conducting Si electrodes 2. When light is absorbed onto the p-doped region, an electron is introduced into the conduction band and a hole is left in the valence band 3. Electron is attracted to the region beneath the positive electrode where it is stored. 4. The hole migrates to the n-doped substrate where it combines with an electron 5. Electrons stored in each pixel of top row are moved into the serial register at the top and then moved 1 pixel at a time to the top where the charge is read out and this is repeated until the entire array has been read out to the amplifier
What were the problems with embedding NO-releasing particles in the outer membrane of the sensor?
1. Particles not homogeneous 2. Because we could only embed a few particles (upper limit), we reduced the amount of NO
In assessing the performance of glucose monitoring sensors, what are the parameters that are looked at?
1. Performance: operational durability, sensitivity, accuracy 2. Biocompatability: inflammatory cell recruitment and collagen capsule density
Why was a diabetic porcine model needed to test glucose monitoring?
1. Pigs have human-like skin 2. They needed a diabetic pig becasue there is less NO production in tissue with diabetes than tissue without diabetes
What is the problem with the current glucose monitoring devices?
1. Poor accuracy: not reflective of blood glucose because of the foreign body response (protein adsorption, macrophages and neutrophils infiltrate and try to digest the foreign body and when they cannot they fuse together and form giant cells and these cells suck away oxygen and glucose, so you cannot measure blood glucose values 2. They do not work for long because of foreign body response 3. Infection 4. Can be dislodged if you are active
What can cause false pregnancy negatives?
1. Procedures improperly followed (Improper urine collection or improper delay prior to reading results) 2. Premature Testing too soon for sufficient accumulation of hCG
What is the goal of Dr. Schoenfisch's work for CF patients?
1. Reduce # of pills patients take 2. Develop drugs that are both antibacterial and mucolytic 3. Provide alternate to existing antibiotic therapy that resistance is emerging for
What are the advantages of using gradient elution?
1. Reduced analysis time 2. overall resolution of the mixture improved 3. better peak shape because we don't have a lot of tailing or broadened peaks from being in the column for so long 4. improved sensitivity
What 2 things can happen when light encounters another medium:
1. Reflection off the surface 2. Refraction through the medium with a bending of the path
What are the ideal characteristics of detectors?
1. Response to wavelengthss over a broad range 2. Sensitivity for small amounts of lights 3. Low background signal (dark current) 4. Rapid response (how rapid depends on what you study) 5. Output proportional photon flux
Why doesn't nitric oxide affect mammalian cells?
1. They are bigger 2. Have a way keeping superoxide levels low (enzymes), therefore oxidative stress is highly unlikely to happen in mammalian cells 3. They are around NO
What are the disadvantages of double-beam scanning spectrophotometers?
1. They are expensive 2. More moving parts so they might break easier
Why do we separate compounds?
1. To isolate or concentrate components from a mixture 2. To separate component(s) from other species that would interfere in analysis
How do OTC pregnancy tests work?
1. Urine is applied to the nitrocellulose wick 2. Liquid flows from left to right 3. Liquid encounters the detection reagent on the conjugate pad which contains an hCG antibody + red colored gold nanoparticles and hCG is bound. 4. Continues to flow and the hCG and Ab1 are trapped by Ab2 which binds to hCG at the test line 5. Gold nanoparticles make a red line at the test line 6. Liquid continues right until it meets the control line that has antibodies that bind to Ab1. 7. Positive: 2 red lines, negative: 1 red line, fail: no lines which means an invalid test
What are the 3 characteristics of capillary electrophoresis?
1. Very fast 2. High efficiency 3. especially useful for biopolymers like proteins
What are the 3 steps of atomization in a furnace?
1. drying 2. charring 3. atomization
What can give false pregnancy test positives?
1. hCG also produced by trophoblast cells in some diseases 2. Biochemical pregnancy...egg implantation begins but fails 3. Hormonal hCG supplementation
Why is capillary electrophoresis so efficient?
1. no particles so no multiple paths (A = 0) 2. no stationary phase so no RMT (C = 0)
1. What is the pH of 0.02 M H2CO3 (Ka1=4.46 x 10^-7, Ka2=4.69x10^-11) 2. What is the equilibrium concentration of HCO3- 3. What is the fraction of the species in the fully deprotonated form?
1. pH=4.02 2. 9.45 x 10^-5 M 3. 2.33 x 10^-9
A triprotic acid H3PO4 has Ka1 = 7.11 x 10^-3, Ka2=6.34x10^-8, Ka3=4.22x10^-13. You are asked to titrate 50 mL of 0.1 M H3PO4 with a 1 M solution of NaOH. What is the pH for the following amounts of titrants added: 1. 9.00 mL 2. 10 mL 3. 18 mL
1. pH=7.8 2. 9.74 3. 12.64
What does nitric oxide do?
1. prevent platelet adhesion and clotting. 2. Antimicrobial 3. vasodilator 4. angiogenesis 5. tumoricidal 6. neurotransmission 7. inflammatory rersponse
What is the wavelength, wavenumber, and name of radiation with an energy of 100 kJ/mol?
1.20 um, 8.36x10^3 cm-1, infrared
Copper I (Cu+) reacts with neucuproine to form the colored complex (neocuproine)2Cu+ that absorbs light (λmax of 454 nm.) A 5.0 mL aliquot of a 25.0 mL unknown solution presumed to contain copper is mixed with 1.0 mL of reagents, diluted to 50.0 mL with buffer, and mixed thoroughly. A 4.0 mL portion of this solution is transferred to a cuvet and placed into a spectrophotometer. The absorbance is measured to be 0.421 at 454 nm. The absorbance of a blank solution (4.0 mL aliquot of a solution containing the same reagents except Cu+ is also measured (Ablank = 0.101). A 10.0 μl aliquot of 1.0 x 10-3 M Cu+ is then mixed into the cuvet containing the unknown and an absorbance jumps to 0.868 at 454 nm. What is the concentration of Cu+ in the unknown sample?
1.8 x 10^-5 M
What type of noise can be theoretically eliminated?
1/f noise
What is pink noise?
1/f noise or drift noise
What is frequency?
1/t; the number of complete oscillations that waves make per second
What is the path length of the flame in absorption atomic spectroscopy?
10 cm
What is the IR region?
10-12,500 cm-1
How many different pregnancy tests are there now?
100
What is the wavelength range of lasers?
100 to 10,000 nm (UV, Vis, IR)
If a given sample absorbs no light, what is % transmittance?
100%
What is the Kovat's index for a linear alkane?
100x the number of carbon atoms
In a He-Ne laser, what is the ratio of helium to neon?
10:1
How long does vibrational relaxation take?
10^-12 seconds
How long does UV-Vis absorption take?
10^-15 seconds
Due to the Doppler effect and pressure broadening, what are line widths in atomic spectroscopy like?
10^-3 to 10^-2 nm
How fast is fluorescence?
10^-6 to 10^-10 seconds
In a PMT, how many electrons are finally collected at the anode for each photon striking the cathode?
10^6
If the S/N ratio of an emission spectrum is 0.9, how many spectra must be averaged to get a S/N ratio of at least 3?
12
What heat is used for drying in a furnace? For how long?
125C for 20 seconds
What is the range of a NiChrome wire?
1300 to 500 cm^-1
What heart is used for charring in a furnace and for how long?
1400 C for 60s
What is the threshold hCG for a pregnancy test positive?
15mlU
A 4.37 mg sample of protein is digested to form NH3 to back calculate how much nitrogen is in the protein. Path length is 1 cm. We take 10 mL of sample with 10 mL of phenol and 2 mL NaOCl. Then it is diluted to 50 mL. We take 1 mL and put it into the cuvette to measure absorbance, which is 0.592! Prepare a blank and the absorbance is 0.140. For a reference, we take 0.0100g of NH4Cl (MW: 53.49) dissolved in 1 L of water, then we take 10 mL and dilute it to 50 mL. The absorbance of reference is 0.308. • What is the weight percent of nitrogen in the protein sample?
16.1 %
When did OTC pregnancy tests become available?
1975
If a grating has 1x10^3 grooves/cm, what is the groove spacing?
1x10^-3 cm
How many subunits is hCG?
2
What is the pKa of silanol?
2
Convert a wavelength of 4000nm into wavenumber.
2,500 cm-1
If both analyte X and standard S have concentrations of 10 mM and the area under the peak is 2.3x greater for the analyte. What is the response factor?
2.3
Determine the Fe3+ concentration in ground water. Fe3+(colorless) + SCN-1(colorless) --> FeSCN2+ (absorbs at 580 nm) A 15 mL aliquot of well water was treated with an excess of SCN1- and diluted to 100 mL and an absorption measurement was made (1 mL into cuvet...1 cm) and an absorbance was measured 0.394 For reference, a 50 mL standard solution of the complex FeSCN2+ at 1.54 x 10^-5 M was made. Exactly 1 mL of this solution was transferred to a cuvet and Abs=0.850. Without FeSCN2+ the absorbance of the solution was 0.260. Determine the concentration of Fe2+ in well water.
2.3 x 10^-5 M
w1/2 is equal to what?
2.35σ; width at half peak
A solution in a capillary electrophoresis experiment has an electroosmotic mobility of 4.7 x 10-8 m2/Vs) at pH 4.0. How long will it take a neutral solute to travel 52 cm from the injector to the detector if 27 kV is applied across the 62-cm-long capillary tube at pH 4.0?
2.5 x 102 sec
What is the wavelength range of a deuterium arc lamp?
200-400 nm
How many pregnancy tests are purchased every year?
20M
What heat is used in atomization in a furnace and for how long?
2100C for 10 seconds
What is the range for a Nernst glower?
25000 to 500 cm^-1
Blue Dextran 2000 (molecular mass of 2.00 x106) was eluted during gel filtration in a volume of 26.40 mL from a 2.00 x 34.97 cm (diameter x length) column of Sephadex G-50. The fractionation range of G-50 is from 1,500 to 30,000 molecular weight. Radioactive NaCl is eluted at a volume of 109.8 mL. 1. At what retention volume would hemoglobin (molecular mass 64000) be expected? 2. What would the retention volume of a protein be if Kav for the protein is 0? 3. What would the retention volume of a protein be if Kav for the protein is 0.65? 4. What is Kav for a protein with a MW of 1200? 5. If Kav for a protein was 1.3, what could you conclude about this solute?
26.4 mL, 26.4 mL, 80.6 mL, 1, adsorption was happening
0.1 mM KMnO4 has an absorbance maximum of 0.26 at 525 nm in a 1 cm cell. Find the molar absorptivity and the concentration of a solution whose absorbance is 0.52 at 525 nm in the same cell.
2600 M-1 cm-1, 0.2 mM
Visible light strikes the surface of benzene at a 45˚ angle. At what angle does the light ray pass through benzene? Air n: 1.00029 Benzene n: 1.5
28˚
If we are making emission measurements, how many wavelength selectors do we have?
2; one before and after the sample. One is held constant
If we are making absorption and fluorescence measurements, how many detectors do we have?
2; one is in the line of the light source and the fluorescence is 90˚ to the light source
CCDs store photo-generated charge where?
2D pixel array
What is the basal level of hCG?
2mlU
What is a good S/N?
3
By 2050, diabetes is predicted to approach what percentage of adults?
30%
What is the wavelength range for a tungsten lamp?
320-2500 nm
Visible light travels from air into water at a 45˚ angle. At what angle does the light ray pass through the water? Water n: 1.33 Air n: 1.00029
32˚
What are the number of vibrational states for a linear molecule?
3n-5
What are the number of vibrational state for a nonlinear molecule?
3n-6
How many pregnancy tests were available in 1975?
4
When 2 mg/mL pyrene and 2.5 mg/mL perylene were separated by HPLC, relative peaks areas of 590 and 640 cm2 were obtained. A fresh solution was then made by mixing the 5 mg perylene with 1 mL of unknown solution containing pyrene but no perylene. The mixture was diluted to a final volume of 5 mL. HPLC resulted in observed peak areas of 402 and 421 cm2 for pyrene and perylene. Determine [pyrene] in the unknown solution.
4.14 mg/mL
How many mL of 0.2 M HNO3 should be added to 215 mL of 0.008 M ethylamine (CH3CH2NH2) to a solution of pH=10.52 in a final volume of 500 mL? The pKa is 10.636.
4.87 mL
How many pills does the average CF patient take/day?
40
What is the range of a Globar source?
4000-200cm^-1
What is the average life of a CF patient?
41
w is equal to what?
4σ; width at baseline between 2 tangents drawn to the steepest parts of the peak
If our particles are 3 microns in diameter, what is the lowest our plate height can be?
6 microns
A solute with a partition coefficient of 3.00 is extracted from 100.0 mL of phase 1 into phase 2. What volume of phase 2 is needed to extract 95% of the solute in one extraction? What is the total volume of phase 2 needed to remove 95% of the solute in five equal extractions instead?
633 mL 137 mL
A fiber optic has a core with n= 1.25 and cladding with n= 1.13. Calculate the minimum angle for total internal reflection to occur in this system.
64.7˚
How many conceptions are there annually?
6M+
By how many kilojoules per mole is the energy of O2 increased when it absorbs UV radiation with a wavelength of 147 nm? How much is the energy of CO2 increased when it absorbs IR with a wavenumber of 2300 cm-1?
814 kJ/mol 28 kJ/mol
Copper I (Cu+, colorless) reacts with a reagent to form a colored complex that absorbs light (λmax of 454 nm.) A 2.00 mL aliquot of a 100.0 mL unknown solution presumed to contain copper is mixed with 1.00 mL of reagents, diluted to 10.0 mL with buffer, and mixed thoroughly. A 4.00 mL portion of this solution is transferred to a cuvet and placed into a spectrophotometer. The absorbance measured at 454 nm is 0.421. The absorbance of a blank solution (4.0 mL) containing the same reagents but no Cu+ is 0.101. Lastly, the absorbance of a 4.00 mL aliquot of a 1.25 x 10^-6 M Cu+ solution measured at 454 nm is 0.305. Based on this information, what is the concentration of Cu+ in the unknown sample?
9.81 x 10^-6 M
Some biomolecules require pores of what size in microporous silica?
> 30 nm
What is a good resolution?
>1
In packed columns, what Van Deemter terms contribute to band broadening?
A B C
Decreasing particle size affects which terms in the Van Deemter equation?
A and C since solute can equilibrate between phases more rapidly becasue the distance that it has to diffuse is smaller
How is molecular mass determined in SEC?
A calibration curve is made of logMW vs. elution volume. To figure out the molecular weight of unknowns we can compare the elution volume to that of the standards
What happens in vibrational relaxation?
A cascade down excited vibrational levels. No electronic levels
What is a faux porous bead?
A faux porous shell around a solid bead core.
What is chromatography?
A method to separate components in a mixtures based on different distribution coefficients between the 2 phases based on the interaction between the solute and the stationary phaase
Why do the absorption and emission transitions not overlap? Why is the emission spectrum at a lower energy than the absorption spectrum?
A molecule absorbing radiation is initially in its ground state, S0 and it possesses a certain geometry and solvation. The electronic transition to excited state S1 is faster than the vibrational or translational motion of atoms or solvent molecules. When radiation is 1st absorbed, the excited S1 still has S0 geometry and solvation. After excitation, the geometry and solvation change to their most favorable values for the S1 state and this lowers the energy of the excited molecules. Also, when the S1 molecule fluoresces and returns to the S0 state, it still has S1 geometry and solvation, which has a higher energy than S0. Therefore, emission energy is less than excitation energy
How is an atomic emission experiment carried out?
A nebulized sample is pulled into plasma gas, then measured by a monochrometer or polychrometer and then detected
What is normal phase chromatography?
A polar stationary phase and a less polar or non-polar mobile phase
What type of property is electroosmosis?
A solvent property. Before we even put the solute in there is electroosmosis going on
The transmittance of a 0.010 M solution of a compound in a 0.1 cm-pathlength cell is T=8.23%. Find A and the molar absorptivity
A=1.02 ε=1.08x10^3 M-1 cm-1
Find the absorbance and transmittance fo a 0.00240 M solutiomn of a substance with molar absorptivity of 313 M-1 cm-1 in a cell with a 2cm pathlength?
A=1.5 T=0.0316
Indicate the type of chromatography, GC, LC, AC, or CE: Antibody-antigen interactions
AC
Which is the best chromatographic technique for the following analysis: GC, HPLC, AC, CE, GPC Determining the presence of an illegal steroid in blood for which you have a monoclonal antibody
AC
In a pregnancy test, what has the enzyme label?
Ab1*
What is the test line?
Ab2 binds all hCG (in hCG-Ab1* complex)
What is the control line?
Ab3 binds all of the unbound Ab1
In a furnace, absorbance reaches its maximum when?
Absorbance reaches a maximum during atomization then decreases as the sample evaporates from the oven
What is the most common flame composition for atomic spectroscopy?
Acetylene/air
How does X-ray fluorescence work?
An incoming X ray knocks an electron from the first two shells of an atom and then higher energy electrons fall into the vacancy and emit an xray called Ka or Kb, and the vacancy left in the other shells is filled by even higher energy electrons accompanied by more x rays
What are examples of lasing media?
Ar gas, Kr gas, ruby crystal, Nd:YAG
What type of gas is used in a plasma flame?
Argon
Stray light arises from what?
Arises from diffraction into unwanted orders and angles and unintended scatter from the optical components and the walls or from outside of the instrument
When does Beer's Law not hold?
At high concentrations, when A > 1
In capillary electrophoresis, what might happen to anions at low pH?
At low pH when electroosmosis is weak, the anion may never reach the detector
In OTC, what Van Deemter terms contribute to band broadening?
B C
What are the disadvantages of gradient elution?
Baseline drift, limits the detectors that we can use because some detectors are sensitive to changes in solvent
In a glucose biosensor, how do we measure the concentration of glucose?
Because glucose is not redox active and we are using an amperometric detector, we use glucose oxidase to produce H2O2, which is what we are measuring
Why is early detection of pregnancy important?
Because it requires changes in lifestyle: hobbies, alcohol, smoking, drugs
How does a UV Vis spectrometer detector work?
Because many solutes absorb UV light, they can create a spectra from an eluting solvent and the spectra can be matched to a library of spectra to identify the compound
Why is the UV-Vis spectroscopy detector zig-zagging?
Because of Beer's Law, A=εbC where b is the path length. If we increase the path length, this can allow the detector to respond to tiny concentrations
What needs to be considered when using an OTC?
Because solute interacts with the walls of the column and in order to give sufficient separation, you need these columns to be longer because the surface area is much less than in a packed column
Why are the absorption and emission spectra mirror images of each other?
Because the spacings between vibrational levels are roughly equal and if the transition probabilities are similar
In capillary electrophoresis, why is the detector placed as close to the anode as possible?
Because we want time for the separation to happen
Why do we need NO release mechanisms, why can't we just use gaseous NO?
Body is run by NO and we do not want it to be released everywhere because that would interrupt a lot of things, we just want it to be released at the sensor surface
What type of stationary phase is used in partition chromatography?
Bonded liquid to the stationary phase. There are no binding sites.
Refractive index detectors measure what type of property?
Bulk
How can interference from a flame be subtracted?
By using D2 or Zeeman background correction
Indicate the type of chromatography, GC, LC, AC, or CE: No A or C terms in van Deemter equation
CE
Which is the best chromatographic technique for the following analysis: GC, HPLC, AC, CE, GPC Separating 2 proteins of similar molecular weight and geometry but different overall charge
CE
What is the reaction for a flame ionization detector?
CH + O --> CHO+ + e-
What are the polar stationary phases that are used for HPLC?
CH2)3N2: can be protonated and depronated at different pHs (CH2)3CN: very polar (CH2)2OCH2CH(OH)CH2OH
What are the non polar stationary phases that are used for HPLC?
CH2)7CH3, (CH2)18CH3, (CH2)3Ph
What is a spectrophotometric titration?
Changes monitored in absorbance during a titration to tell when the equivalence point has been reached
Why does changing wavelength alter molar absorptivity?
Changing wavelength also changes molar absorptivity because all molecules do not absorb all wavelengths of light
X-ray fluorescence energies are independent of what? Why?
Chemical form because the electrons are deep inside of the atom
What is the solution to conventional intra-arterial sensors?
Coating them with nitric oxide
How does atomic emission spectroscopy work?
Collisions in flame or plasma promote some atoms to excited electronic states from which they can emit photons to return to lower energy states. Emission intensity is proportional to the concentration of element in the sample
What causes the red at the test line and control linein a pregnancy test?
Color change results from Ab1* proximity to substrate in support (Ab1* has the enzyme label)
How do we determine the molecular weight in molecular exclusion chromatography?
Compare the Vr of the unknown to that of standards with known molecular weights and a similar strucutre
What is electroosmotic mobility?
Constant of proportionality between electroosmotic velocity and applied field
X-rays can cause molecules to do what?
Core electrons to move
How was the problem of the NO-embedded glucose sensor fixed?
Created nanoparticles
What types of cuvets are used for infrared spectroscopy?
Cuvets with NaCl, polyethylene or KBr
What is the equation for a deuterium arc lamp?
D2 + electrical energy --> D2* --> D2 + hυ
How can we avoid having resistance to mass transfer cause band broadening?
Decrease velocity, decrease the thickness of the stationary phase, increase temperature, decrease column radius
When glucose sensors were coated with NO, what were the advantages?
Decreased scaar rtissue capsule thickness, increased angiogenesis, and lower inflammatory response
How does decreasing particle size affect resolution?
Decreasing particle size increases the number of theoretical plates, increasing resolution. A: the smaller the particles are, the more likely you will have uniform paths. C: if you have smaller particles they will be more packed together and the distance that an analyte has to travel to get to the stationary phase is much smaller
How do we store and release NO in a chemical form since it is a gas?
Diazonium dilolate/MAHMA! It is a chemical NO donors that are stable except with water, and water protonates the nitrogen and liberates the NO
What are 2 factors that affect how well 2 components are separated?
Difference in retention time and peak widths
Separation in capillary electrophoresis is based on what?
Differences in migration of charged ions in an electric field in solution
What is environmental/line noise caused by?
Discrete interferences at discrerte frequencies and constant vibrations
When is a distribution coefficient used?
Distribution coefficient is used in place of the partition coefficient when the species can exist in more than 1 chemical form
What is the A term in the Van Deemter equation?
Eddy Diffusion/multiple paths
Why is plate height decreased when using an open tubular column?
Eddy diffusion cannot occur
What are the causes of band broadening?
Eddy diffusion, longitudinal diffusion, resistance to mass transfer
In the intensity equation, K depends on what?
Efficiency of fluorescence and the light collection efficiency
How does a photomultiplier tube detector work?
Electrons emitted from a photosensitive surface strike a second surface (dynode) that is positive. Electrons are accelerated and strike the dynode with more than their kinetic energy. Each energetic electron knocks more than 1 electron from the dynode. The new electrons are accelerated to a 2nd dynode that is even more positive than the first. Upon striking the 2nd dynode, even more electrons are knocked off and accelerated to a 3rd dynode. Process is repeated and more than 10^6 electrons are collected for each electron striking the first surface
How does a thermocouple detector work?
Electrons have lower energy in 1 conductor than in the other so they flow from one to the other until the resulting voltage difference prevents further flow. Junction potential is temperature dependent because electrons flow back to the high energy conductor at higher temperature.
What is photon emission?
Electrons in an excited energy level relax to the ground energy level, emitting a photon of a given wavelength
The migration speed of substituted benzoic acids results from the combined effects of electroosmotic flow and electrophoretic mobility. The voltage applied to a 0.5 m long capillary is 2.5x104 V. The neutral marker carried by electroosmotic flow requires 188s to travel .4 m from the inlet to the detector. Migration times of benzoate and 2-methylbenzoate are 340 s and 371s respectively. What is the electroosmotic velocity and electroosmotic mobility. What are the apparent and electrophoretic mobilities of benzoate and 2-methylbenzoate? If electroosmotic mobility were 3x10-8 m2/Vs, what would be the migration times of the neutral marker and benzoate?
Electroosmotic velocity: ueo=0.00213m/s electroosmotic mobility: 4.26x10-8 m2/vs Apparent mobility of benzoate: 2.35 x 108 m2/vs electrophoretic mobility of benzoate: -1.91x10-8 m2/vs Apparent mobility of 2-methylbenzoate: 2.16x10-89 electrophoretic mobility of 2-methylbenzoate: -2.1x10-8 m2/vs 267s 734s
what is the dominant form of atomic spectroscopy?
Emission from atoms in plasma is the dominant for of atomic spectroscopy
Why is it important that hCG maintains progesterone levels by placental corpus luteal cells?
Enriches uterine lining with essential vasculature for gestation
What is the sample wick?
Excess Ab1* binds all hCG in sample
Why does an excitation spectrum look like an adsorption spectrum?
Excitation looks like an absorption spectrum because the greater the absorbance at the excitation wavelength, the more molecules are promoted to the excited state and the more emission will be observed
What is vibrational relaxation?
Excited molecule bumps into some solvent and drains some energy. This is a radiationless transition
Why does the FDA only approve glucose monitoring sensors for 5-7 days?
FDA only approves for 5-7 days because there is so much of a foreign body response that they stop working
T/F: Darker lines on subsequent tests indicate hCG doubling
False
T/F: For gradient elution in normal phase chromatography, it is better to move from a more polar to less polar mobile phase solvent
False
T/F: One method for reducing Johnson noise is by using a beam chopper
False
T/F: Prescription medications affect pregnancy tests
False
T/F: The detector for a fluorescence instrument is 90˚ with respect to the source to account for drift
False
T/F: UTIs affect pregnancy tests
False
The resolution of a grating is proportional to the number of grooves and inversely proportional to the diffraction order, true or false?
False
The use of an operational amplifier is one useful method for minimizing noise, true or false?
False because it just gives better signal to noise
What are the 2 most sensitive detectors?
First PMT, then CCD
Compare flame and furnace on: Speed Complexity Sample volume LOD Type of samples
Flame is faster flame is more simple flame has large sample volumes, furnace has small Furnaces have better limits of detection Flames only have liquid, where furnaces take liquid or solid
What stimulates an egg to ovulate?
Follicle stimulating hormone (FSH)
How are the results in capillary electrophoresis quantified and why?
For quantative analysis, normalized peak areas are required, so peak area divided by migration time. This is because in chromatography each analyte passes through the detector at the same rate, the peak area is proportional to the quantity of the analyte, but in electrophoresis, analytes with different apparent mobilities will pass through the detector at different rates, and the higher the mobility, the less time it will spend in the detector. To correct for time spent in the detector, we must divide by migration time
Why does an OTC create a greater resolution?
For the same length and applied pressure, the linear velocity in an OTC column is much higher, so an OTC can be made 100x longer than a packed column and still have the same linear velocity and pressure drop. If plate height is the same, the longer column provides 100x more theoretical plates, leading to 10x the resolution and band spreading by Eddy diffusion cannot occur
What explains why the absorption and emission peaks do not overlap?
Franck Condon Principle
What are ideal absorption values?
From 0 to 0.5
Electron capture detectors are used for what type of chromatography?
GC
Flame ionization detectors are used for what type of chromatography?
GC
Indicate the type of chromatography, GC, LC, AC, or CE: Kovat's Retention index
GC
Indicate the type of chromatography, GC, LC, AC, or CE: Temperature programming
GC
Indicate the type of chromatography, GC, LC, AC, or CE: Thermal conductivity detector
GC
Thermal conductivity detector is used for what type of chromatography?
GC
Which is the best chromatographic technique for the following analysis: GC, HPLC, AC, CE, GPC Separating compounds in automobile exhaust
GC
Which is the best chromatographic technique for the following analysis: GC, HPLC, AC, CE, GPC Determining the molecular weight of a polymer you synthesized
GPC
What are the 2 ways that nitric oxide can be delivered?
Gas or in a NO donor
What does GPC stand for?
Gel permeation chromatography
Nitric oxide works against what type of microbes?
Gram+, Gram- and fungi
What are the 2 relevant parameters for a grating?
Groove spacing (d) and groove angles
Write the van Deemter equation for open tubular gas chromatography, including all necessary terms.
H = B/v + Cv H=plate height B=longitudinal diffusion C=mass transfer rate v=linear velocity
What is the most polar mobile phase that can be used in LC?
H2O
What is the Van Deemter equation?
H=A+B/V+Cv
Refractive index detectors are used for what type of chromatography?
HPLC
Size exclusion chromatography is what type of chromotohraphy?
HPLC
Which is the best chromatographic technique for the following analysis: GC, HPLC, AC, CE, GPC Identifying a non volatile pollutant in drinking water
HPLC
Amperometric detectors are used for what type of chromatography?
HPLC and CE
Conductometric detectors are used for what type of chromatography?
HPLC and CE
Potentiometric detectors are used for what type of chromatography?
HPLC and CE
UV-Vis Spectroscopy detectors are used for what type of chromatography?
HPLC and CE
What are the carrier gases used in gas chromatography?
He, H2, N2
What is the unit of frequency?
Hertz
What does HPLC stand for?
High performance liquid chromatography
How did Hippocrates determine pregnancy?
Honey and water given before bed and if the woman was pregnant they had pain and cramps
What is intensity?
I; power per unit solid angle
KBr cuvets can be used for what wavelength range?
IR
NaCl cuvets can be used for what wavelength range?
IR
Thermocouple detectors detect what range of wavelengths?
IR
Vibrational excitations can be caused by what minimum type of light?
IR
What does scattering do to the data collected?
If it is scattering the light, the molecules that it is scattering is the light shown on the cuvette (P0). It makes it look that the amount of light that is being absorbed is lower and so the concentration is underestimated
Why is it important that HPLC detectors are insensitive to solvent changes?
If we use gradient elution, we do not want background changes
When would we use a filter?
If you are doing very careful research, you will use a filter in addition to a monochrometer!
What causes cystic fibrosis?
In CF there is a mutated protein that alters chloride transport in the lungs and this auses thick mucus to build up in the lungs
What is the critical angle?
In an optical fiber, any angle of incidence greater than this will result in total internal reflection
Proteins can be assayed in what region?
In the UV region at 280 nm
In polarized light, the electric field oscillates how?
In the xy plane
How do we increase velocity in capillary electrophoresis?
Increase the applied voltage
How can we decrease shot noise?
Increase the current or number of photons
What are the advantages of using faux porous beads over porous beads?
Increases surface area a bit Mass transfer is faster (decreases C) More uniform column packing (decreases A) Partially porous molecules with a total diameter of 2.7 um have a similar Van Deemter curve as a fully porous particle with a diameter of 1.8 um, but the partially porous molecule doesn't require the high pressures
Increasing stationary phase thickness does what in GC?
Increasing stationary phase thickness increases the retention time and increases the resolution of early eluting peaks (see equation for resolution)
What are the disadvantages of ICPMS?
Isobaric interference, high cost
What does it mean to be photosensitive?
It emits electrons when struck by UV or visible light
Why is tailing bad?
It impacts the ability to resolve 2 different peaks and it is also hard to quantify
In GC, what is accomplished by reducing the diameter of the column?
It increases efficiency by increasing the rate at which solute equilibrates between phases
In a grating monochrometer, what does a wider slit do?
It increases the amount of light and signal, but it might also distort the spectrum because more wavelengths are getting through
How can we decrease Johnson/Gaussian noise?
It increases with temperature, so we can cool down the detector to create less noise
Where is the detector that measures fluorescence placed and why?
It is 90˚ from the light source because fluorescense and/or phosphorescence is a low light phenomenon (part of the reason is because not all molecules fluoresce and not all transitions will fluoresce) and if we were trying to measure fluorescence in the path of the actual light it would not work. This would be like lighting a candle on a sunny day and holding it in front of the sun and trying to see it
Describe the structure of Human Chorionic Gonadotropin (hCG)
It is a dimeric glycoprotein with α and β subunits that are held together by electrostatic interactions
What is the capillary made of in capillary electrophoresis?
It is a fused silica capillary with aa polyamide coating
What does the Van Deemter/Plate Height Theory say?
It is a measure of column efficiency and it says that separation occurs in discrete stages called plates. can predict column performance based on the following properties, which will all impact resolution: ◦ Phase properties ◦ Solution diffusion ◦ K (partition coefficient) ◦ Phase thickness ◦ Size of the stationary phase ◦ Flow rate ◦ Porosity
What is a beam chopper?
It is a tool that is used in a double-beam scanning spectrophotometer and it spins. Half is reflective and half is open space. It lets some light through to the sample, but also the mirror reflects light down into the reference cuvette
What does a monochrometer do?
It is a wavelength selector; it selects disperses light into its component wavelengths to send only a narrow band of wavelengths through the sample or detector because we are only interested in either 1 or a narrow selection of wavelengths
What are refractive index detectors?
It is based on the refraction of light as it passes from one media to the next. The presence of a solute changes the refractive index of the solvent
How can we tune the surface of the silica stationary phase support?
It is coated with SiOH groups which can be reacted with different things and the surface can be covalently modified
Describe the light that a laser gives off?
It is coherent, high intensity, bright, polarized, collimated
What is Johnson Noise/Gaussian Noise due to?
It is due to movement of free charge character in any resistive element that creates a greater voltage drop.
In HPLC, what is the mobile phase?
It is solvent. There are a lot of different solvents we can use and a lot of variability
If you are looking at a molecular mass calibration graph made from SEC, how do you determine VO?
It is the linear point on the left
How do we calculate V0 for a SEC calibration curve?
It is the volume at which the vertical line starts. Any compound within this vertical area is excluded
What is an IR spectra used for?
It is used to fingerprint molecules because different molecules have different IR spectra that are so different that we can identify molecules based on the functional groups
What is molecular size exclusion used for?
It is useful in determining size and size range for polymers, proteins, etc
What is desalting?
It is when molecular exclusion chromatography is used to purify macromolecules in biochemistry because salts of low molecular mass or any small molecule can be removed from solutions of larger molecules
What does a linear detector response mean?
It means that the detector response is proportional to concentration
Do we need NO to be released continuously, or just during the foreign body response (initial 5-7 days)?
It needs to be released for the entire 28 days
Why was the goal of designing electrochemical sensors for the continuous monitorring of blood gases aand electrolytes important?
It provides clinicians with better guidance for treating unstable patients and alerts them of abrupt changes in these physiologically important parameters
What is the plate theory?
It says that separation occurs in discrete stages/plates (mini-extractions). It says there is a separation every time the solute in the mobile phase interacts with the stationary phase. Assumes a column is mathematically equivalent to a plate column equilibrium established for solute to be between mobile and stationary phase on each plate, but it neglects solute diffusion and flow path
What is a Van Deemter curve?
It shows the plate height as a function of flow rate in mL/minute
Downside of a solid stationary phase in GC?
It will give strong retention of solutes because of the large surface area, which means the peak will not be very sharp
In affinity chromatography, why do we change pH, add a surfactant, or change the ionic strength of the solution...why can't we just want for the antigen to come off?
It would come off after a long time, and the antigens would not all come off at once and we want them to come off at once so we get a sharp peak that we can quantify
What are the types of white noise?
Johnson/Gaussian and Shot noise
What types of noise are not frequency dependent?
Johnson/Gaussian and shot noise
Indicate the type of chromatography, GC, LC, AC, or CE: Gradient elution
LC
Indicate the type of chromatography, GC, LC, AC, or CE: Ocadecyl (C18) bonded silica
LC
Indicate the type of chromatography, GC, LC, AC, or CE: Refractive index detector
LC
What type of flow do we get in LC?
Laminar flow because there is some friction
A large partition coefficient means what about how long a solute stays on the column?
Large K means that the solute is on the column for a long time
How does fluorescence atomic spectroscopy work?
Lase irradiates atoms in the flame to promote atoms to an excited electronic state from which they can fluoresce and return to the ground state
Why do we not want to make slits in a grating monochrometer too small?
Less signal means less signal to noise ratio...so if the slit is too small the spectrum is too noisy
What is a double beam spectrophotometer?
Light alternately passes through the sample and the reference, directed by rotating mirror (chopper) into and out of the light path. When light passes through the sample, the detector measures irradiance P and when the chopper diverts the beam through the reference duvet, the detector measures P0. This provides an automatic correction for changes of source intensity and detector response with time and wavelength because the power emerging from the two samples is compared frequently
How dose light enter a furnace?
Light from a hollow cathode lamp travels through windows at each end of the tube
When measuring light absorption, what is the basic setup needed?
Light source --> wavelength selector --> sample --> detector
When glucose sensors were coated with NO, what were the disadvaantages?
Loading with NO collapses the pore structure and the membrane permeability, so we get no rersponse
What is a bulk property detector?
Looks at the overall change of the solvent because the solvent properties changes as an analyte goes through it
What is the downside of packed GC columns?
Lower resolution necause of a high surface area and this gives a lot of places for the solute molecules to interact, so we get a wide peak; Eddy diffusion
What is the disadvantage of using OTC over packed columns?
Lower sample capacity means cannot do preparative work
What is pulse width like in the chronic phase?
Lower than in the acute phase, but still greater than what it was at implantation
What stimulates the corpus luteum to generate progesterone?
Lutenizing hormone (LH)
Atomic spectroscopy allows us to do what?
Measure absorbance, emission, and fluorescence
What is the eluent strength (ε)?
Measure of solvent adsorption on base silica. The more polar the solvent, the greater its eluent strength for adsorption chromotograph with bare silica. The greater the eluent strength, the more rapidly solutes will be eluted from a normal phase column
How do we measure an excitation spectrum?
Measured by varying excitation wavelength and measuring emitted light at one particular wavelength
What does absorption spectroscopy do?
Measures light absorption of a sample as a fraction of the wavelength of light
What is the most common stationary phase support in HPLC?
Microporous silica (SiO2)
What is V0 in SEC?
Mobile phase/void volume. It is the volume of the mobile phase that goes right through. The volume outside of the gel
How are ground state molecules in a lasing medium gotten to the excited state?
Molecules in the ground state of the lasing medium are pumped into the excited state by radiation from a powerful lamp or electric discharge.
What are the advantages of lasers?
Monochromatic, high intensity, coherent, directional (polarized)
What is population inversion?
More electrons in the excited state(s) that the ground state; necessary for lasing