LONGITUDINALLY MODULATED CRYOGENIC SYSTEM - A GENERALLY APPLICABLE APPROACH TO SOLUTE TRAPPING AND MOBILIZATION IN GAS-CHROMATOGRAPHY

This paper describes a novel approach to solute trapping and remobiliz ation. It involves the use of a subambient trap, with a narrow capilla ry column passing through the cooled region. A mechanism allows for lo ngitudinal movement of the trap relative to the chromatographic column or narrow transfer line through which analytes travel. Either the tra p or the column can be moved, and the frequency or manner of relative movement determines the type of result obtained. A series of prelimina ry studies are described that define the general approach to using thi s device and demonstrate the unique benefits that may arise from the m odulation movement. Significant improvement (reduction) in peak width occurs if the device is placed immediately prior to the detection syst em, and consequently a great increase in detection limits results. Wit h a 25 cm length of capillary column between the trap and detector, it is calculated that the plate height of dodecane is 0.082 mm, equivale nt to 12 100 plates/m. This was found to be much greater than that for dodecane analyzed on a 25 m column, By slow displacement of the colum n through the trap, it is demonstrated that the solute is trapped in t he first 1 cm (or less) of the column located in the cold trap.