Plate Theory and Extensions - Vacancy Chromatography > Page 77


Equation (65) is very similar to that obtained by Reilly et al.. (20) but the derivation is simpler, as those authors utilized the approximate binomial form of the elution curve in their procedure. Scott et al. (21) provided some experimental evidence supporting equation (65). The mixture contained uracil, hypoxanthine, guanine and cytosine, each present in the mobile phase at a concentration of 14 mg/l. The column employed was 1m long, 1.5 mm I.D., packed with a pellicular cation exchange resin and operated at a flow rate of 0.3 ml/min.

Courtesy of the Journal of Analytical Chemistry (ref. 21)

Figure 20. Vacancy Chromatograms for the Separation of a Four Component Mixture


The mobile phase was a 0.14 M potassium phosphate buffer solution adjusted to pH 4.0. Figure 20 reveals that the positions of the peaks are accurately predicted by the theory; the peak heights differ because the relative responses of the detector to the different bases were not taken into account in calculating the theoretical curves. The sample with excess concentration of solutes over that in the mobile phase, shown as a chromatogram with positive peaks, is almost exactly the mirror image of the negative chromatogram produced from the injection of 115 ml of pure mobile phase.