STUDIES ON CRYOGENIC TRAPPING OF SOLUTES DURING CHROMATOGRAPHIC ELUTION IN CAPILLARY GAS-CHROMATOGRAPHY

Cryogenic trapping of solutes leads to narrowing of the chromatographi c band. By placing the trap at the end of a capillary column, it is po ssible to study the effectiveness of the trap in terms of producing a sharpened elution profile. The trap may be heated by supplementary hea ting, but here convective heating from the GC oven is employed simply by turning off the cryogenic coolant. It is estimated that it takes ab out 50 s for the trap to heat up sufficiently to allow trapped solute to be remobilized, although this depends upon the oven temperature and thermal mass of the trap. It can also be shown that the more volatile solutes mobilize faster from the trap in this particular mode of oper ation. The recovery of trapped components shows that there is essentia lly quantitative trapping, and the solutes are trapped just at the lea ding edge of the trap.