Analytical Chemistry

H (cm) 0.635 0.510 0.423 0.465 0.552 0.632 0.692 0.749

cm s–1) 0.91 1.51 3.0 4.2 5.55 7.0 8.0 9.0

Plot a graph of H versus and calculate the optimum gas velocity, the corresponding minimum plate
height and the maximum plate number.

(10) The separation of two compounds on a packed and a capillary column gave the following data:

dead volume, cm^3

adjusted retention volume, cm^3

Packed column

15

Capillary column

3.0

component A^160 1.1

component B^170 1.2

number of theoretical plates (^6400) 25 600
Which column is giving the better resolution and why?
(11) A mixture of methyl esters of fatty acids was chromatographed on a Carbowax 20 M column
giving the following peak areas and detector response factors:
Ester Peak area, cm 2 Response factor
methyl-n-butyrate 2.95 0.81
methyl-iso-valerate 0.86 0.88
methyl-n-octanoate 1.66 0.98
methyl-n-decanoate 4.52 1.00
Calculate the percentage composition of the mixture by internal normalization.
(12) An HPLC separation of a two-component pharmaceutical product yielded the following data:
Compound Retention time
(chart distance) mm
Peak width at base
mm
Peak width at 1/2-
height mm
solvent 30 — —
aspirin 75 6.5 3.0
caffeine 86 8.1 3.25
Calculate:
(a) the capacity factor, k, for each compound;
(b) the plate number for each compound using base widths;