Instrumental Analysis Final Study Guide

True or False: For most substances, Beer's law holds in diluted solutions (< 0.01 M). a)True b)False

a) True

735 mg of quercetin in 100 mL water was extracted with an equal volume of isopropyl ether. The layers were separated; the ether evaporated. The residue was found to contain 585 mg of quercetin. What is the partition coefficient? a)3.90 b)0.796 c)1.26 d)0.256 e)4.90

a)3.90

The (M + 1)+ to M+ peak height ratio for nicotinic acid, C6H5NO2 , (M = 123.11) is: (The isotope contributions for 13C = 1.08%, 2H = 0.015%, 15N = 0.368%, and 17O = 0.038% per atom.) a)7.00% b)0.898% c)1.11% d)1.50% e)6.55%

a)7.00%

True or False: In a magnetic field mass spectrometer, the spectrum of masses is obtained by varying the magnetic field strength. a)True b)False

a)True

True or False: Ion-exchange resins are used for separation of small molecules while ion-exchange gels are used for large molecules. a)True b)False

a)True

True or False: Raman scattering is different from Rayleigh scattering in that some of the incident radiation undergoes frequency changes. a)True b)False

a)True

True or False: Sensitivity with an inductively coupled plasma is enhanced by using piezoelectric crystal as an ultrasonic nebulizer. a)True b)False

a)True

True or False: Superficially porous particles allow fast mass transfer of macromolecules into the thin porous layer. a)True b)False

a)True

True or False: The purpose of a guard column is to protect the analytical column from contamination. a)True b)False

a)True

True or False: The separation between two components in a mixture depends on the ratio of their partition coefficients between mobile and stationary phases. a)True b)False

a)True

True or False: The slope of a Stern-Volmer plot equals the formation constant of a complex between the fluorescent species and the quencher. a)True b)False

a)True

True or False: Thicker stationary phases are suitable for separation of volatile compounds. a)True b)False

a)True

True or False: Weak-acid resins are used for separation of proteins and peptides. a)True b)False

a)True

Which of the following stationary phases would be appropriate to separate a mixture of hydrocarbons? a)diphenyl polysiloxane b)cyanopropylphenyl polysiloxane c)polyethylene glycol d)biscyanopropyl polysiloxane e)arylene polysiloxane

a)diphenyl polysiloxane

A flame ionization detector is: a)mass sensitive. b)concentration sensitive. c)specific. d)nondestructive. e)sensitive to nonhydrocarbons.

a)mass sensitive.

The most intense peak in the mass spectrum is called: a)the base peak. b)the molecular ion. c)the adduct. d)the protonated molecule. e)the fragment.

a)the base peak.

True or False: Oxygen sensors are based on the significant increase of fluorescence intensity. a) True b) False

b) False

Two compounds, A and B, were separated by gas - liquid chromatography. The retention times are 628 s and 642 s, and the widths at half-height are 8.3 s and 9.4 s, correspondingly. Find the resolution for these two compounds. Are the peaks well resolved? a)1.6, yes b)0.93, no c)0.93, yes d)7.5, yes e)3.8, yes

b)0.93, no

What resolving power is needed to separate N2+ and CO+ ions with masses 28.0061 and 27.9949? (use m/Dm definition) a)1.00 b)2.50 × 10^3 c)5.00 × 10^3 d)4.00 × 10^-4 e)1.12 × 10^-2

b)2.50 × 10^3

True or False: A compound with MH+ = 151 has an odd number of nitrogen atoms. a)True b)False

b)False

True or False: In partition chromatography, ions in mobile phase are attracted to counterions covalently attached to stationary phase. a)True b)False

b)False

True or False: Raising the column temperature increases the retention time. a)True b)False

b)False

True or False: Spectrophotometric photodiode array detector is based on the photoelectric effect. a)True b)False

b)False

True or False: The purpose of a monochromator in the atomic spectroscopy is to isolate narrow monochromatic lines from source. a)True b)False

b)False

Which of the following interferences can be minimized by using releasing agents? a)spectral b)chemical c)isobaric d)ionization e)None of the above.

b)chemical

Reversed-phase chromatography uses a: a)polar stationary phase and less polar mobile phase. b)less polar stationary phase and more polar mobile phase. c)constant mobile phase composition. d)continuous change of solvent polarity during elution. e)continuous temperature change during elution.

b)less polar stationary phase and more polar mobile phase.

Which of the following is not an advantage of the electrophoretic methods with respect to chromatography? a)higher resolution b)scaling up to a preparative separations c)less amount of solvents needed d)lower analysis time e)more simple equipment

b)scaling up to a preparative separations

Gradient elution in ion-exchange chromatography may mean: a) changing the polarity of the eluent. b) increasing the temperature of the system. c) increasing the ionic strength of the eluent. d) modifying the rate flow of the eluent. e) continuously increasing the pressure.

c) increasing the ionic strength of the eluent.

The UV/Vis spectrum of acetone has two absorption maxima at 187 nm and 273 nm. The lowest energy absorption is due to: a) s - sigma* transition. b) p - pi* transition. c) n - pi* transition. d) s - pi* transition. e) n - sigma* transition.

c) n - pi* transition.

Two species, A and B, form a complex with composition AaBb. The method of continuous variations was used to find the stoichiometry and the maximum absorbance was observed at mole fraction of B = 0.200. The stoichiometry of the complex is: a)A2B2 b)A2B c)A4B d)AB4

c)A4B

A solution of NaCl is passed through a protonated cation-exchange resin. The eluate will contain: a)NaCl b)H2O c)HCl d)HCl + NaCl e)Cl-

c)HCl

In the van Deemter equation, H @ A + B/ux + Cux, where ux is the flow rate, A is the multiple path term, B is related to the longitudinal diffusion, and C is related to the equilibration time. Which of the following is true? a)The longitudinal diffusion can be minimized by slower linear flow. b)The parameters A, B, and C, depend on the stationary phase only. c)The equilibration time C is related to the rates of mass transfer through the stationary phase and through the mobile phase. d)The multiple path term A is important for open tubular columns. e)The multiple path term A = 0 for packed columns.

c)The equilibration time C is related to the rates of mass transfer through the stationary phase

Dispersion of a grating means: a)ability to distinguish two closely spaced peaks. b)bending of light by the grating. c)ability to produce angular separation of adjacent wavelengths. d)reflection from a flat reflective surface. e)loss of energy due to the interaction with the particles of the medium.

c)ability to produce angular separation of adjacent wavelengths.

Intersystem crossing is: a) a nonradiative transition between states with the same spin. b) a radiative transition between states with different spin. c) a radiative transition between states with the same spin. d) a nonradiative transition between the vibrational levels of the same electronic state. e) a nonradiative transition between states with different spin.

e) a nonradiative transition between states with different spin.

Which of the following applies to mass spectra from chemical ionization? a)The nitrogen rule does not apply. b)Abundance of fragment ions is observed. c)Small or absent molecular ion peak is observed. d)No ions higher than m/z = M+. are observed. e)Adduct ions with m/z higher than MH+ can be observed.

e)Adduct ions with m/z higher than MH+ can be observed.

Refraction is: a)amplification of light due to constructive interference. b)change in direction of propagation at the interface between two different media. c)bending of light due to passing through media with different refractive indices. d)loss of energy when passing from less dense to more dense medium. e)bending of light by a grating.

c)bending of light due to passing through media with different refractive indices.

Polychlorinated biphenyls (PCBs) are major environmental pollutants. Which of the following detectors would be most suitable for GC analysis of PCBs? a)flame ionization (FID) b)thermal conductivity (TCD) c)electron capture (ECD) d)nitrogen-phosphorus (NPD) e)flame photometric (FPD)

c)electron capture (ECD)

A disadvantage of a silica-based stationary phase is: a)high porosity, which retains some of the mobile phase. b)high surface area. c)exposed silanol groups on the column that create adsorption sites. d)difficulty to control size. e)fast mass transfer between stationary and mobile phase.

c)exposed silanol groups on the column that create adsorption sites.

Which of the following is NOT true about flow injection analysis? a)Liquid sample is injected into a continuously flowing liquid carrier. b)The sample reacts with a reagent in the liquid. c)The same conditions must be applied in every run. d)Reactants and products are in equilibrium. e)Typical analysis times are tens of seconds.

d)Reactants and products are in equilibrium.

Extracted ion monitoring means: a)monitoring 1-5 m/z values. b)all emerging substances contribute to the signal. c)ions pass through consecutive mass filters. d)all m/z values are measured but only one is displayed at a time. e)to add up the total current of all ions and all masses detected above a selected value.

d)all m/z values are measured but only one is displayed at a time.

8.17 × 10-19 J of energy are needed to eject an electron from the surface of Na. The longest possible wavelength (nm) of light that can ionize the metal is: a)876 nm. b)185 nm. c)243 nm. d)563 nm. e)350 nm.

c) 243nm

The Doppler effect is one of the reasons for line broadening in the atomic absorption and emission. Which of the following factors increases magnitude of Doppler broadening? a)higher atomic mass b)decreasing temperature c)higher velocity of the absorbing or emitting species d)higher number of atoms moving perpendicular to the transducer's path e)higher concentration of atoms in the plasma

c)higher velocity of the absorbing or emitting species

If the electroosmotic mobility, meo, is faster than the electrophoretic mobility, meo, of an anion, the latter will: a)move toward the anode. b)not move. c)move toward the cathode. d)be part of the diffuse layer close to the wall. e)form an ion pair with the present cations.

c)move toward the cathode.

The term "column bleeding" refers to: a)leak of carrier gas from the column. b)poor resolution of low volatility compounds. c)stationary phase decomposition. d)decomposition of analytes on the column. e)stationary phase contamination.

c)stationary phase decomposition.

The laser medium is irradiated with electromagnetic radiation at an energy that equals exactly the energy difference between the ground and excited state. What is the function of this incident radiation? a)creates population inversion b)promotes an electron to higher energy level c)stimulates emission of a photon d)stimulates nonradiative deactivation e)amplifies the emitted light

c)stimulates emission of a photon

The distribution coefficient, D, is defined as: a)the ratio of the concentrations of a solute, S, in the organic and in the aqueous phase. b)the ratio of the masses of the solute, S, in the organic and in the aqueous phase. c)the ratio of the total analytical concentrations of a solute, S, in the organic and in the aqueous phase. d)the equilibrium between the deprotonated and protonated form of a substance in each phase. e)the ratio of the concentrations of the noncharged species in the organic and in the aqueous phase.

c)the ratio of the total analytical concentrations of a solute, S, in the organic and in the aqueous phase.

The maximum volume of sample injected in HPLC is limited by: a)the column diameter. b)the polarity of the stationary phase. c)the size of the loop. d)the sensitivity of the detector. e)the volume of the available syringe.

c)the size of the loop.

Two solutions, A and B, of a certain compound, have absorbances AA = 1 and AB = 2. Which statement about the relation between their transmittances, TA and TB, is correct? a)TA = 2 × TB b)TA = 0.1 × TB c)TB = 100 × TA d)TA = 10 × TB e)TB = 2 × TA

d) TA=10xTB

How much H+ is released when 50 mL of 4.0 mM Ca2+ are retained on a cation exchange column? a)0.20 meq b)0.60 meq c)2.0 meq d)0.40 meq e)4.0 meq

d)0.40 meq

Calculate the wavelength for first-order diffraction when polychromatic light strikes a grating at 50° and the angle of diffraction is 20°. The grating has 2500 blazes/mm. a)400.0 nm b)1.108 nm c)4.432 × 10-4 nm d)443.2 nm e)221.6 nm

d)443.2 nm

Which of the following statements is true about fluorescence? a)It is faster than absorption. b)The fluorescence efficiency decreases when the temperature decreases. c)It is a T1 - S0 transition. d)It occurs from the lowest vibrational level of the excited state. e)Fluorescence comes at longer wavelengths than phosphorescence.

d)It occurs from the lowest vibrational level of the excited state.

The most common source in atomic absorption is the hollow-cathode lamp. Which of the following statements is not true about the hollow-cathode lamp? a)Doppler broadening and pressure broadening are reduced. b)The anode and the cathode are sealed in a glass tube. c)The ionized inert gas is sputtering off atoms from the cathode. d)It produces single-wavelength monochromatic radiation. e)The performance of the lamp depends on the ionization potential of the carrier gas.

d)It produces single-wavelength monochromatic radiation.

Which of the following statements is NOT TRUE about the isosbestic points? a)This is the wavelength where the absorption spectra of two species with a constant total concentration cross each other. b)The total absorbance does not change during a chemical reaction, or a physical change of the sample. c)The molar absorptivity of the species is the same. d)More than two species exist in equilibrium. e)The total analytical concentration remains the same.

d)More than two species exist in equilibrium.

Which of the following gases cannot be used as a GC carrier gas? a)N2 b)CO2 c)H2 d)N2O e)Ar

d)N2O

The atomic absorption and emission spectra consist of sharp lines while the molecular spectra exhibit broad absorption bands. This is because: a)the atomic absorption and emission are faster than the corresponding molecular processes. b)high temperature increases the population of the atomic excited states. c)atomic spectra are recorded in the gaseous phase only. d)atomic energy levels do not have vibrational and rotational sublevels. e)molecular peaks are broadened by the solvent.

d)atomic energy levels do not have vibrational and rotational sublevels.

Capillary electrophoresis provides high resolution because: a)applied electric field moves ions in one direction. b)low viscosity of the solution provides low friction. c)multipath term in the van Deemter equation is eliminated. d)both the multipath and mass transfer components are absent. e)longitudinal diffusion is eliminated.

d)both the multipath and mass transfer components are absent.

Which of the following is not an HPLC detector? a)ultraviolet detector b)fluorescence detector c)evaporative light-scattering detector d)flame ionization detector e)charged aerosol detector

d)flame ionization detector

Immunoassays employ antibodies to measure macromolecules in quantities as low as a nanogram. The sensitivity of the method is due to: a)formation of a colored, or fluorescent product. b)specific binding of the antibody 1 to the analyte, which results in strong fluorescence. c)covalent bonding between the enzyme and antibody 2. d)one enzyme molecule, which participates multiple times in catalysis producing more of the colored/fluorescent product. e)antibody 2, which binds competitively with the analyte and releases a colored/fluorescent product in the solution.

d)one enzyme molecule, which participates multiple times in catalysis producing more of the colored/fluorescent product.

Which of the following devices can be used as an infrared detector? a)photomultiplier tube b)tungsten lamp c)Nernst glower d)photoconductive detector e)photodiode array

d)photoconductive detector

Derivatization can be applied in HPLC in order to: a)increase the volatility of the compounds. b)improve the thermal stability of the analyte. c)increase the size of the molecules. d)prepare compounds suitable for UV and fluorescence detection. e)eliminate matrix interferences.

d)prepare compounds suitable for UV and fluorescence detection.

Tailing, a distortion of the Gaussian bandshape, occurs when: a)too much solute has been loaded to the column. b)the flow rate is inappropriate. c)the temperature is unstable. d)some sites retain solute more strongly than other sites. e)there is a gas leak in the system.

d)some sites retain solute more strongly than other sites.

One reason why small particles improve the performance of an HPLC column is: a)that they increase the flow rate. b)that they increase the pressure of the mobile phase. c)that they reduce the analyte's time on the stationary phase. d)that they provide more uniform flow through the column. e)that they cause higher temperature as a result of increased frictional heating.

d)that they provide more uniform flow through the column.

Laser ablation methods are not good for quantitative analysis due to poor accuracies. The reason for this is: a)only a small amount of material is removed by ablation. b)lack of appropriate calibration standards. c)low detector sensitivity. d)the composition of the elements in the plasma may not match the composition of the sample. e)The spectral resolution is low.

d)the composition of the elements in the plasma may not match the composition of the sample.

Which of the following light sources emits light as a result of blackbody radiation? a)deuterium lamp b)laser c)laser diode d)tungsten lamp e)xenon lamp

d)tungsten lamp

The function of the reflection part of a time-of-flight mass spectrometer is to: a)accelerate the ions toward the detector. b)increase the resolving power of the instrument. c)collide with ions of lower energy. d)turn around ions toward the grid in front of the detector. e)separate ions of the same mass by kinetic energy.

d)turn around ions toward the grid in front of the detector.

Which of the following statements is NOT true about an excitation spectrum? a)It is nearly the same as the absorption spectrum. b)It is a mirror image of the emission spectrum. c)It is collected at variable excitation and fixed emission wavelength. d)It has a higher energy than the emission spectrum. e)It is collected at constant excitation and variable emission wavelength.

e)It is collected at constant excitation and variable emission wavelength.

Which of the following is not related to decreasing the exit slit width? a)Sharper, better resolved peaks are recorded. b)It decreases signal-to-noise ratio. c)The radiant power decreases significantly. d)It decreases the effective bandwidth. e)It reduces the stray light.

e)It reduces the stray light.

Which of the following statements is not true about isobaric interference? a)It is observed in inductively coupled plasma-mass spectrometry method (ICP-MS). b)It refers to poor resolution of ions with the same or similar mass-to-charge-ratio. c)It can be reduced by replacing the collision cell with a dynamic reaction cell. d)Interfering species are reduced by chemical reactions. e)It results in lower detection capability compared to inductively coupled plasma-atomic emission spectrometry (ICP-AES).

e)It results in lower detection capability compared to inductively coupled plasma-atomic emission spectrometry (ICP-AES).

The following figure shows the extraction efficiency of different metal ions by dithizone into CCl4 at different pH. Which of the following statements is true? a)Cu(II) can be extracted selectively in the presence of Ag(I) and Pb(II) at pH 5. b)Zn(II) can be extracted selectively in the presence of Pb(II) at pH 8. c)Bi(III) can be separated from Sn(II) by selective extraction at pH 5. d)At pH 9, most Cd(II) will be in the organic phase. e)Sn(II) can be extracted selectively in the presence of Tl(I) and Cd(II) at pH 5.

e)Sn(II) can be extracted selectively in the presence of Tl(I) and Cd(II) at pH 5.

Which of the following statements is NOT TRUE about fluorescence quantum yield for a photochemical process? a)It is the ratio of the emission and absorption rates. b)It is the ratio of the emitted vs. the absorbed photons. c)It does not depend on the absorption efficiency. d)It decreases in presence of a quencher. e)The values of the quantum yield are from 0 to (proportionality).

e)The values of the quantum yield are from 0 to (proportionality).

In which case is on-column injection appropriate? a)when high resolution is required b)to dilute the sample c)when the sample is contaminated d)when there are high molecular weight compounds e)for quantitative analysis

e)for quantitative analysis

Which of the following statements is not true about aptamers? a)consist of DNA or RNA base pieces b)more stable than the antibodies c)can bind to molecules of different sizes and structures d)bind specifically to the target e)form strong covalent bond with the target species

e)form strong covalent bond with the target species