Quality test of a mechanical switching valve for two-dimensional open tubular gas chromatography

A commercially available mechanical micro switching valve has been tested for inertness. The test mixtures used were a modified Grob test and a solution consisting of eight typical aroma compounds, both at the 2-ng level. Cryogenic focusing of the sample after chromatography including one passage through the valve revealed that irreversible interaction of some test substances with valve components was rather small. A composite main peak of a chromatogram from a fruit juice aroma exhibiting a “mixed odor” was selectively transferred (heart-cutting) to a second column and resolved into three peaks. GC-GC/sniffing assigned a minor peak to a substance formerly hidden under the composite peak. Separate heating of the valve during temperature programming of the column was found to be unnecessary.