A solvent passes through a chromatography column in 3.0 minutes, but the solute requires 9.0 minutes.

(a) What is the retention factor, k?

(b) What fraction of the time does the solute spend in the mobile phase in the column?

The volume of the stationary phase is 0.18 times the volume of the mobile phase in the column. (Vs = 0.18Vm.)

(c) What is the partition coefficient, K, for this system?

(a). 2

(b). 1/3

(c). 11.11

Explanation:

(a). k = (t₍s₎-t₍o₎) / t₍o₎ ... (1)

where k = retention factor,

t₍o₎=solvent time, t₍s₎ = solute time.

Given t₍s₎=9.0 Minutes, t₍o₎=3.0 minutes.

∴ k = (9-3) / 3

k = 2.

(b). the fraction of time the solute spend in the mobile phase in the column is the ratio of the solvent time to the solute time. = t₍o₎/t₍s₎ ... (2)

= 3/9

=1/3.

(c). K=k (Vm/Vs) ... (3)

where K = partition coefficient, k = retention factor, Vm=volume of mobile phase, Vs = volume of stationary phase.

∴K = k (Vm/Vs)

k=2, and Vs=0.18Vm.

∴K = 2 (Vm/0.18vm)

⇒K = 2/0.18

∴K=11.11