The following data has been calculated from the chromatogram. The column is 100

Question

The following data has been calculated from the chromatogram. The column is 100 cm long and the unretained marker takes 2 minutes to be detected. Calculate the resolution for the peaks (A-B, B-C). How long must the column be in order to have baseline resolution? Assume the plate height, flow rate, selectivity and retention factor (capacity factor) will remain constant. If you use a shortcut equation in calculating the resolution, justify.

Explanation / Answer

Formula,

Resolution (Rs) = {[sq.rt.(N)[(alpha - 1)/alpha][k/(1 + k)]}/4

with,

N = plate number

alpha = ratio of retention factors

k = retention factor for higher peak

For A-B,

N = (2450 + 2500)/2 = 2475

alpha = 7.8/6.4 = 1.22

k = 7.8

Resolution (Rs) = {[sq.rt.(2475)[(1.22 - 1)/1.22][7.8/(1 + 7.8)]}/4

                          = 2.0

For B-C

N = (2500 + 2850)/2 = 2675

alpha = 8.8/7.8 = 1.13

k = 8.8

Resolution (Rs) = {[sq.rt.(2675)[(1.13 - 1)/1.13][8.8/(1 + 8.8)]}/4

                          = 1.3

With plate height (H) a constant, the column length (L) is directy proportional to the plate number (N)

L = H x N

H = constant

So the length of column would be dependent upon the plate number in both the cases for the baseline resolution.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.