The following data are for a liquid chromatographic column: Length of packing 24

Question

The following data are for a liquid chromatographic column:

Length of packing

24.7 cm

Flow rate

0.313 mL/min

VM

1.37 mL

VS

0.164 mL

A chromatogram of a mixture of species A, B, C, and D provided the following data:

Retention time

(min)

Width of base peak

(min)

Nonretained peak

3.1

_

A

5.4

0.41

B

13.3

1.07

C

14.1

1.16

D

21.6

1.72

Calculate:

a. The retention factor (k) for each peak

b. For species B & C, calculate:

i. The resolution (R) between the peaks

ii. The relative retention factor (alpha)

Length of packing

24.7 cm

Flow rate

0.313 mL/min

VM

1.37 mL

VS

0.164 mL

Explanation / Answer

Calculate the Retention Factor for A,B,C and D.

KA=(5.4-3.1)/3.1 =0.74

KB=(13.3-3.1)/3.1 =3.3

KC=(14.1-3.1)/3.1 =3.5

KD=(21.6-3.1)/3.1 =6.0

b. For species B & C, calculate:

i. The resolution (R) between the peaks

Rs=[tr (C) –tr(B)]/(wb+wc)/2]

Rs=[14.1 –13.3)]/(1.07+1.16)/2]=0.72

ii. The relative retention factor (alpha)

alpha=(14.1 –3.1) / (13.3-3.1)=1.08

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