A gas chromatography column was operated under the following conditions: Column

Question

A gas chromatography column was operated under the following conditions:

Column dimension: 1.1 M length x 2.0 mm internal diameter Retention times: Nonretained carrier gas, tm = 0.30 min Compound A retention time, trA = 1.98 min Compound B retetntion time trb = 4.16 min Compound C retention time, trc = 7.93 min Peak widths at base : 0.18, 0.41, 0.82 min for A, B, and C respectively.

Calculate: i) the retention factor, k” for each compound ii) the selectivity factor, for each adjacent pair of compounds iii)

Explanation / Answer

Given,

tm = 0.3 min

trA = 1.98 min

trB = 4.16 min

trC = 7.93 min

i) Retention factor for A, kA = (trA - tm)/tm = (1.98 - 0.3)/0.3 = 5.6

Retention factor for B, kB = (trB- tm)/tm = (4.16-0.3)/0.3 = 12.86

  Retention factor for C, kC = (trC- tm)/tm = (7.93-0.3)/0.3 = 25.43

ii) Selectivity factor for B and A , Alpha = kB / kA = 12.86/5.6 = 2.29

Selectivity factor for C and B , Alpha = kC / kB = 25.43/12.86 = 1.98

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