In gas chromatography, the dependence of the adjusted retention time, tr\', on t
ID: 1059345 • Letter: I
Question
In gas chromatography, the dependence of the adjusted retention time, tr', on temperature, T, is shown in the following equation,
where a and b are constants for a specific compound on a specific column. When the column temperature is 398.5 K, a compound elutes at tr' = 10.81 min. The same compound elutes from the column at tr' = 24.09 min when the column temperature is decreased to 375.5 K. Calculate the constants a and b for this compound on this column.
Predict the adjusted retention time for this compound on the same column at 361.6 K.
In gas chromatography, the dependence of the adjusted retention time, t', on temperature, T, is shown in the following equation, log t where a and b are constants for a specific compound on a specific column. When the column temperature is 398.5 K, a compound elutes at t' 10.81 min. The same compound elutes from the column at tr' 24.09 min when the column temperature is decreased to 375.5 K. Calculate the constants a and b for this compound on this column. Number Number min K min Predict the adjusted retention time for this compound on the same column at 361.6 K. Number mindExplanation / Answer
log (tr) = a / T + b
Case 1:
T = 398.5 K, tr = 10.81 min
log (10.81) = a / 398.5 + b
1.034 = a / 398.5 + b … (1)
Case 2:
T = 375.5 K, tr = 24.09 min
log (24.09) = a / 375.5 + b
1.382 = a / 375.5 + b … (2)
Equation (2) – (1) gives,
1.382 – 1.034 = a ( 1 / 375.5 – 1 / 398.5)
0.348 = a / 6505.946
a = 2264.14 min.K
Putting value of a in equation (1) we get,
1.034 = 2264.14 / 398.5 + b
b = -4.65 min
Retention time, tr’
log (tr’) = 2264.14 / 361.6 – 4.65
log (tr’) = 1.614
tr’ = 41.08 min