Moving cryogenic modulator for the comprehensive two-dimensional gas chromatography (GC x GC) of surface water contaminants

The modulation system in a comprehensive two-dimensional gas chromatograph (GC x GC) can be regarded to be the heart of the analyzer. Different ways of modulating the effluent of the first column into very narrow pulses and injecting these onto the fast second column have been demonstrated. Modulation can be established by applying heat, as in the first existing types of modulators, the two-stage heated modulator and the Sweeper system. It can also be performed by applying cooling, as was demonstrated in the "longitudinally modulated cryogenic system." Cryogenic systems have mechanical and applicational advantages over heated systems, as they are easier to install and maintain and do not need positive temperature differences to remobilize the analytes. A homemade moving cryogenic modulator was evaluated for use in a GC X GC system for the separation of(very) polar and nonpolar surface water contaminants. The results demonstrate that the performance of this less complex modulator is very comparable to the earlier reported types of modulators. It is further demonstrated that GC x GC is a very suitable technique to fully separate complex mixtures, such as surface water contaminants. The obtained separation appeared to be complete and peak identification was facilitated. (C) 2001 John Wiley & Sons, Inc.