New liquid nitrogen cryogenic modulator for comprehensive two-dimensional gas chromatography

A new liquid nitrogen (LN2)jet-based thermal modulator for performing comprehensive two-dimensional (2D) gas chromatographic (GC x GC) separations has been designed and constructed. Temperature measurements of the trapping zone, a segment of uncoated fused silica capillary, show that it can be cooled to - 196degreesC in about 300 ms. A film of liquid nitrogen develops on the outside of the trapping capillary even when the oven temperature is in excess of 200degreesC. Compounds as volatile as propane can be trapped by the modulator and held for periods of at least 1 min without breakthrough. The peak widths for n-alkanes are on the order of 80 ms at half height after passing through an 80 cm second dimension column. Repeated analysis of gasoline demonstrated excellent run-to-run reproducibility of the system. (C) 2003 Elsevier B.V. All rights reserved.