Solid-phase microextraction with different fibers

Solid-phase microextraction (SPME) — is a procedure originally developed for sample preconcentration in gas chromatography (GC). In this procedure a small-diameter fused silica optical fiber, coated with a liquid polymer phase such as poly(dimethylsiloxane), is immersed in an aqueous sample solution. The -> analytes partition into the polymer phase and are then thermally desorbed in the GC injector on the column. The same polymer coating is used as a stationary phase of capillary GC columns. The extraction is a non-exhaustive liquid-liquid extraction with the convenience that the organic phase is attached to the fiber. This fiber is contained in a syringe, which protects it and simplifies introduction of the fiber into a GC injector. Both uncoated and coated fibers with films of different GC stationary phases can be used. SPME can be successfully applied to the analysis of volatile chlorinated organic compounds, such as chlorinated organic solvents and substituted benzenes as well as nonvolatile chlorinated biphenyls. 

Several analytical approaches are employed to quantify sulphur volatiles in wine among them, the headspace procedure, such as the Purge and Trap, and solid-phase microextraction methods, combined with GC coupled to different detectors, was shown to be quite effective (Mestres et al., 2000 Rauhut et al., 1998). Recent papers suggest that the HS-SPME technique, with an improved choice of fiber coating phases, would be one of the more promising approaches for the concurrent measurement of compounds with different boiling points (Mestres et al., 2002 Fang and Qian, 2005). 

The newly developed solid-phase microextraction (SPME) technique, first reported by Pawliszyn in 1989, is increasingly used for the gas chromatographic determination of a wide variety of volatile and semivolatile organic compounds in water or aqueous extracts of different substrates. Basically, it involves the extraction of specific organic analytes directly from aqueous samples or from the headspace of these samples in closed vials. The extraction is achieved onto a fused-silica fiber coated with a polymeric liquid phase. After equilibration, the fiber containing the absorbed or adsorbed analyte is removed and thermally desorbed in the hot injector port of a gas chromatograph or in an appropriate interface of a liquid chromatograph. ... 

Three different extraction volumes (2,4, and 8 mL) were tested with SPME extraction time set to IS min. The solid-phase microextraction time studied was IS, 30, and 60 min viiile die water volume was set to 4 mL. In order to study the fiber carryover effect in GC analysis, the total thermal desorption time (at 250 °C) was set to 10 min. Two sets of experiments were performed 1-min thermal desorption followed by 9-min desorption, and S-min desorption followed by S-min desotptioa... 

As described earlier (4,5), we have studied nestmate recognition by examining the differences of cuticular hydrocarbons between species, colonies, and castes. Briefly, we developed a methodology for the extraction of termite cuticular hydrocarbons by solid phase microextraction (SPME). Both headspace SPME, where the termites were heated in a vial to 120 °C with the fiber 1 cm above the termites, and direct contact SPME, where live termites walked on the SPME fiber for a certain time period, were studied. As shown in Figure 1, both methods were comparable to the normal hexane extraction method in the types of cuticular hydrocarbons that were extracted. Since SPME requires less manipulation of the sample and may use living termites, it may have advantages. 

Table 1 Headspace Compositions of a Blue Hyacinth Collected with Different Commercially Available Solid-Phase Microextraction (SPME) Fibers...

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