theory of chromatographic analysis of drugs

what of A,B,C is dependent on flow rate

B and C

retardation factor depends on what 5 things

1. compound 2. solvent system 3. adsorbent (nature and thickness) 4. amount of material 5. temperature

factors influencing peak shape (3)

1. eddy diffusion -----A 2. longitudinal diffusion------- B 3. resistance to mass transfer----C

what is HETP proportional to

A+ B/u + Cu （u is an optimal flow rate to generate hte smallest value of HETP and provide the best peak shape and separation. )

what is theoretical plate or column efficiency (N)

EQUATION: N= 5.54 (retention time of the peak/ width at half maximum peak height)^2 height of theoretical plate HETP= length of column/ # of theoretical plates

what is peak resolution's english letter

R (band broadening)

higher the concentration, the higher the peaks

true

what are 3 types of modern chromatography

TLC, HPLC, GC

KNOW CALCULATION FOR THEORETICAL PLATE AND HETP

YEA!!!!!

B increases with higher flow rate and C decreases with higher flow rate

false. B decreases with higher flow rate, C increases with higher flow rate

column or liquid chromatography (5 types of separation techniques)

adsorption, ion exchange, normal phase or reversed phase HPLC, size exclusion, affinity

what determines the retention time of a compound

affinity, polarity, ph, column composition, flow rate, mobile phase, length of column

how is chromatography discovered

by tswett, to separate plant pigments first chromatography column was filled with chalk and was used to separate plant pigment extracted into petroleum ether. column was eluted with petroleum ether and was type of adsorption chromatography

what is peak trailing

chromatograpm peaks are not vertical lines, b/c not all molecules in the sample interact equivalently with resin and mobile phase

A is a property of what?

column

what is stationary and mobile phase

column and solvent

parameters that decrease column efficiency and increase column efficiency

decrease: low flow rate, large particle size of stationary phase, thick stationary phase coating, irregular shaped particles of stationary phase, low temp, uneven stationary phase coating, non uniform stationary phase particle size, low diffusion coefficient in mobile phase and stationary phase increase: all opposite of decrease

what is selectivity factor (alpha)

describes how well one analyte interacts with chromatography column compared to another analyte (higher alpha means better selectivity to separate the 2 analytes) KNOW EQUATION!!

what is void volume

empty space not occupied by chromatography separation material

ratio of peak areas of drug and ES are measured and compared to that of standard drug

false. ratio of peak area of drug and its IS is measured and compared to the standard (ES) which also contains IS

the more the theoretical plate, the shorter compound will stay in the column

false. the longer it will stay in the column

contribution of B to band broadening decreases as what increases

flow rate

modern chromatography is used for what (3)

for analytical technique for drug analysis to identify and determine purity of drug products, to assay drug content

what is capacity factor (k')

how well an analyte interacts with chromatography column compared to unretained compound there's an EQUATION FOR THIS!!!!! higher k' means compound interacts more readily with resin and longer

difference between external and internal standards

internal standard is a different compound with similar structure. it controls for extraction efficiency and small variation in HPLC injection volume

the more time analyte molecules spend in the eddies, the more the peak broadens depends on property of waht

of the column

what is chromatography

physical method of separating two or more components based on their distribution between stationary phase and mobile phase

application of chromatography

qualitative: identify drug substance by its chrom characteristics (tR or Rf) in specific chrom system quantitative: assay of concentration of drug based on area under a peak relative to stand; assay of drug substance in presence of other drug or impurities (ie. a drug containing 2 or more drugs or one drug with an impurity)

WHAT is van deemter equation, and what is it related to

relates HETP to the 3 factors: eddy diffusion, longituindal diffusion, resistance to mass transfer

longitudinal diffusion= ?

resistance of analyte being chromatographed to diffusion into the mobile phase.

what is resistance to mass transfer

resistance of analyte being chromatographed to diffusion into the stationary phase (packing material)-- this decreases at low flow rates and high temperature

external standards (ES)

solution of known conc of the same drug being analyzed are prepared!! (different from internal standard, this is the exact same drug used) then analyte can be identified by its tR and its concentration can be determined from peak area relative to External standard

what is eddy diffusion (A)

some analyte molecules take a direct path through the column and others end up in "eddies" and then re-enter the main flow stream of the column at a later time

retention time definition

time taken for an analyte to elute from the chromatography column and be detected by monitoring device (ie. UV detector) look at time to peak!!!

what is Vo (void volume) equal to

to x flow rate to is the time taken for an unretained molecule to pass through the void volume(ie. solvent and things that don't interact with the column comes out at to)

WHAT IS retardation factor (Rf)

value is the ratio of teh distance travelled by the compound divided by distance travelled by solvent. k and alpha values can be calculated from Rf values