THRESHOLD CRITERIA USED FOR THE OPTIMIZATION OF SELECTIVITY BY TUNING INTERMEDIATE PRESSURE FOR SERIES-COUPLED COLUMNS IN A DUAL-OVEN SYSTEM

A computer-assisted procedure based on threshold criteria was employed for the optimization of selectivity by tuning the column coupling-point carrier gas pressure of two capillary columns of different polarities operated at different temperatures in a dual oven gas chromatograph using constant inlet and outlet carrier gas pressures. The optimization procedure was monitored by optimization criterion (Cp) calculated from the following equation: Cp= Σ1nmi + (tR.max - tR, n)/t R.max, where n is the number of solutes in a sample, mi= 1 if the resolution of peak pair is higher than a threshold, tR.maxIs the maximum acceptable analysis time, and tR, nis the last peak retention time. Three kinds of thresholds were compared in this paper: constant threshold; floating threshold predicted from the resolution factor; floating threshold predicted from the separation numbers. The use of a resolution factor calculated for each peak pair gave the best result. A comparable result was obtained by using the floating threshold. However, the last procedure was less tedious than the procedure based on the resolution factor. © 1990, American Chemical Society. All rights reserved.