Shape selectivity: A key factor in comprehensive two-dimensional gas chromatographic analysis of toxic PCBs

A number of toxic planar PCBs, that is, PCB 77, 105, 118, 126, 156, and 169, were successfully separated from other PCB congeners present in technical PCB formulations using comprehensive GC X GC. The planar PCBs were selectively retained using a liquid crystal column, which was used as the first-dimension column. A short and narrow bore (0.25 In. X 0.1 mm) nonpolar 5%-phenyl-methylpoly-siloxane column was used as the second-dimension column. A longitudinally modulating cryogenic system (LMCS) was used to modulate the first-dimension signal. Since the planar PCBs elute from the first column at relatively high oven temperatures they were rapidly eluted from the second column. Altogether, this resulted in a significant peak sharpening, and a 20-fold increase in the signal-to-noise ratio, as compared to standard one-dimensional GC. This column set also seems to separate seven frequently measured congeners, that is, PCBs 28, 52, 101, 118, 138, 153, and 180, from other major PCB congeners. (C) 2001 John Wiley & Sons, Inc.