ABSTRACT:
The use of headspace adsorbent traps in combination with gas chromatography was evaluated for the determination of volatile constituents (e.g. higher alcohols and other congeners of alcoholic fermentation) in spirits. The headspace trap technology comprises of an enhanced static headspace system that allows enrichment and focusing of analytes on adsorbent traps prior to gas chromatographic separation. In contrast to SPME and SPDE that apply small fibres or coated capillaries with sorbent volumina of 0.94 mm3 or 5.99 mm3, respectively, the headspace traps used in this study are tubes packed with a solid sorbent with a significantly greater volume of 160 mm3. In the first step, the traps are loaded by pressurizing the sample vials and allowing the pressure to decay through the cooled adsorbent trap. Then, they are dried by passing carrier gas through the trap to remove moisture from the sample. Finally, the analytes are thermally desorbed and transported by the carrier gas into the GC column for separation. The headspace analysis was performed with the PerkinElmer TurboMatrix HS-110 trap automatic headspace sampler with trap enrichment and flame ionization detector (PerkinElmer, Shelton, USA). A capillary column Rtx 1701 (60 m x 0.530 mm I.D.; 1.5 µm film thickness) with phenylcyanopropyl phase from Restek was used. It was determined that the air toxic phase material, which is also the standard material provided by the manufacturer, was best suited for the analytes under investigation.
In comparison to static headspace sampling, 35-55 times higher peak areas were achieved. For the purpose of spirit analysis, using this one cycle provided adequate sensitivity. If a higher sensitivity is required, e.g. in the case of blood analysis of drinkers of alcoholic beverages to substantiate claims of drinking, up to four trap enrichment cycles (so-called pulsed headspace extraction and trap) can be used to achieve even lower detection limits.
An excellent agreement of analysis results in comparison to the European reference procedure was found (R>0.98, p<0.0001). The fully automated headspace trap procedure requires only minimal sample preparation and is easy to apply.
