Question

An unretained solute passes through a chromatography column in 2.1 min while the analyte requires 9.6 min.

a) Calculate the capacity factor (retention factor) for the analyte.

b) The volume of the mobile phase is 1.4 times the volume of the stationary phase. Find the partition coefficient for the analyte.

Answer 1

a)Retention factor=k=time of retention of analyte in stationary phase/ time of retention of analyte in mobile phase

                              =9.6/2.1

                             =4.571

(The time of retention of analyte in mobile phase is constant for all solutes)

The retention factor (k) is defined as the ratio of time an analyte is retained in the stationary phase to the time it is retained in the mobile phase,

b)

The distribution of a solute between the mobile and stationary phases in chromatography is described by ?, the partition coefficient, defined by:

?=Cs/Cm

where Cs is the concentration of solute in the stationary phase and Cm is the concentration of the solute in the mobile phase.

But concentration of solute is directly proportional to the volume of the phase.

k=volume of stationary phase/volume of mobile phase

=1/1.4=0.71