The benefits of using a Programmed Temperature Vaporizer (PTV) type inlets instead of hot split/splitless (S/SL) inlets for the liquid and headspace (HS) measurements of volatile compounds are shown. We used benzaldehyde as a model compound to show the possibility of oxidation or thermal decomposition of sample compounds in a hot S/SL inlet. Liquid and HS measurements of benzaldehyde in a standard sample as well as its determination in a cherry flavored cola by HS sampling show much higher recovery of the compound when using the PTV. Although we believe that benzaldehyde is oxidized to benzoic acid, we were not able to detect the acid or other degradation products that would show direct evidence for the degradation of benzaldehyde using a HP 5 type column.
In addition we found better peak shapes (especially for the lower boiling compounds), better signal to noise ratios, and therefore better detection limits by using PTVs compared to results obtained for the sample introduced into a hot split/splitless inlet. Similar results are obtained by headspace sampling of volatile compounds from coffee.
The use of a PTV (GERSTEL CIS 4) for Solid Phase MicroExtraction (SPME) measurements has an advantage due to the use of a septumless head (SLH) instead of a septum for sealing the inlet. The significant accumulation of septum material inside the liner by SPME injections is demonstrated. This will lead to higher chromatographic background, restrictions in the flow through the inlet and in worst case to the loss of the fiber. This problem does not appear when using septumless sample introduction systems.
