Time-resolved cryogenic modulation for targeted multidimensional capillarygas chromatography analysis

Multidimensional gas chromatography (MDGC) is performed in a new manner, de scribed in this paper. The method incorporates two directly coupled columns and employs a longitudinally modulated cryogenic trap located between the columns. No heartcutting process is used, but rather a method better termed selected zone compression pulsing is used. Compared with normal MDGC, wher e primary column effluent has to be temporarily diverted either to a monito r detector or to the second dimension column, the new procedure in its simp lest mode passes all of the first column effluent to the second column. It is simply the times at which the modulation of the trap is performed that d etermines which target solutes will be selected for enhanced separation. Th is approach allows almost instantaneous separation of selected zones on the second column, and has the potential to significantly simplify the MDGC me thod. Since data are presented in a time-response format, and do not requir e transformation as previously described for comprehensive GC when using th e longitudinal modulator, quantitation and report generation are essentiall y the same as in any GC method and data system. Advantages also include sig nificant sensitivity improvement. By using cryofocussing, and benefiting fr om the zone compression effects along with fast GC conditions on the second dimension, new possibilities for MDGC can be realised. The method is demon strated by using a mixture of semi-volatile aromatic hydrocarbons. (C) 2000 Elsevier Science B.V. All rights reserved.