Modulation techniques and applications in comprehensive two-dimensional gas chromatography (GCxGC)

More than a decade after Phillips' first published work this article reviews recent developments in comprehensive two-dimensional gas chromatography (GCxGC). Special attention is devoted to the further development and diversity of modulation devices. These include heated sweepers, cryofocused modulators, and a variety of diaphragm valve-switching strategies. It is demonstrated that all modulation approaches can be very well suited to GCxGC, depending on the particular application. Diaphragm-valve modulation is very powerful for volatile organic compounds. Slotted heater and cryofocused modulation are preferred for samples that contain non-volatile components. Applications ranging from petroleum to environmental and biological samples are illustrated. Extension of the technique to GCxGC-mass spectrometry (MS) is also discussed and trends for future research activity are pointed out.