PDMS/DVB fiber

Triacetone triperoxide (TATP) is a powerful explosive manufactured in clandestine laboratories and used by terrorists. As TATP subHmes easily, analysis was performed by SPME trapping of its vapor, using polydimethylsiloxane/divinyl benzene (PDMS/DVB) fiber, followed by desorption into a GC/MS injector [10]. Figure 6 shows the TIC, mass chromatogram and the El mass spectmm of headspace from a debris sample containing TATP [11]. The El mass spectmm contains a molecular ion at m/z 222 and several fragment ions. In the chemical ionization mass spectmm of TATP [12], the m or ions were at m/z 223 (100%), 222 (20%), 133 (20%), 117 (40%), 115 (20%), 103 (75%) and 100 (50%). 

SPME Fiber. A 65 pm poly(dimethylsiloxane)/divinyl benzene (PDMS/DVB) fiber coating (Supelco, Bellefonte, PA) was used in this method. This fiber coating was selected for its ability to retain the derivatizing agent and for its affinity for the PFBOA-aldehyde oxime (7). 

On the other hand, the type of fiber was only important for the lighter PCBs, mainly for PCB-28 and PCB-52. For these compounds, the PDMS-DVB fiber is more efficient than the PDMS fiber. The effect of the fiber factor appeared negative (Figure 2) because PDMS-DVB was selected as its low level (Table 1). For the highly chlorinated PCBs, the two fibers tested seem to have similar performance, and this factor lacks statistical significance. 

PDMS-DVB fibers were analyzed by GC/MS-MS using a Varian 3800 GC with ion... 

HSSPME Extraction Procedure. Manual SPME holders were used with a 100- am poly(dimethylsiloxane) (PDMS) and 65- am poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) fiber assembly (Supelco, Bellefonte, PA). The fibers were conditioned as recommended by the manufacturer. 

PDMS-fibers were analyzed by GC -electron capture detection using a HP 5890 series II GC. PDMS-DVB fibers were analyzed by GC/MS-MS irsing aVarian 3800 GC with ion trap (Varian Saturn 2000). 

Figure 5.4 GC-MS total ion current (TIC) chromatogram of a red Italian wine (Corvina) after HS- SPME automated aroma enrichment using a 1 cm CAR-PDMS-DVB fiber. 1. ethyl acetate, 2. ethanol, 3. isobutyl alcohol, 4. isoamyl acetate, 5. isoamyl alcohols, 6. ethyl hexanoate, 7. methyl heptanoate (I.S.), 8. linalyl ethylether, 9. 1-hexanol, 10. ethyl octanoate, 11. acetic acid, 12. geranyl ethylether, 13. linalool, 14. ethyl decanoate, 15. diethylsuccinate, 16. ethyl 9-decenoate, 17. 2-phenethyl acetate, 18. hexanoic acid, 19. 2-phenylethanol, 20. octanoic acid, 21. decanoic acid...

Table 5.3 Calibration parameters of some aroma compounds in a synthetic wine solution enriched by automated HS-SPME with a 1 cm CAR-PDMS-DVB fiber and analysed by GC-MS. S.D. standard deviation.

In an unpubhshed study, SPME and a 65p,m PDMS/DVB fiber were apphed for extraction of polystyrene (PS) thermo-oxidation products. As seen in Fig. 4, styrene monomer was the main compoimd migrating from the virgin material after low temperatme thermo-oxidation at 80 °C. After 20 weeks, new low molecular weight compoimds including toluene, ethyl benzene, benzaldehyde and acetophenone were also identified. Volatiles migrating from poly(vinyl chloride)/polycaprolactone-carbonate (PVC/PCL-PC) during thermo-oxidation were extracted by PDMS/DVB fiber [19]. The identified compounds included degradation products of PCL-PC, i.e.,... 

Bisphenol A is used as a raw material to make polycarbonate and epoxy adhesives and can coatings. It is also used in flame-retardants, in unsaturated polyesters and in polyacrylate resins. Many foodstuff containers are made of these resins, including containers for oven and microwave cooking. Recent studies have shown that bisphenol type compounds have both mutagenic and cytotoxic properties [84]. Nerin et al. developed a fast screening method based on SPME and HPLC with fluorescence detection suitable for the analysis of several bisphenol derivatives and their degradation products in aqueous canned foods such as tuna, olives and corn [85]. The best results were obtained with carbowax and PDMS/DVB fibers. The detection limits were between 0.7 and 2.4ngmL while RSDs were between 14 and 32%. After the extraction parameters were optimized, the method was applied to... 

Quantitative or semi-quantitative determination of analytes by SPME requires working within the linear dynamic range of the SPME fiber. If the linear dynamic range is exceeded, the extracted amount of analyte will not reflect the amount of analyte in the sample. Figure 2 shows the normalized peak areas for the headspace extractions of different amounts of powdered polyamide 6.6 [67]. The extraction time and temperature were 45 min and 80 °C. Under the given conditions, the dynamic range of the PDMS/DVB fiber was linear if the polyamide sample size was between 1 and 100 mg. For the... 

Fig. 2 The 45-min headspace extractions of 2-cyclopentyl-cyclopentanone from 1 to 1000 mg polyamide 6.6 at 80 °C using a PDMS/DVB fiber. The dynamic range was linear when the sample size was between 1 and 100 mg. Reprinted from [67] with permission of Elsevier. Elsevier (2004)...

Recently, rotundone was identified as a pepper aroma impact compound in Shiraz grapes (Siebert et al.,2008). Identification was achieved by performing GC-MS analysis of grape juice after purification by solid-phase extraction (SPE) using a styrene-divinylbenzene 500-mg cartridge and elution with n-pentane/ethyl acetate 9 1, followed by solid-phase microextraction (SPME) using a 65-pm polydimethylsilox-ane-divinylbenzene (PDMS/DVB) fiber immersed in the sample for 60 min at 35 °C. J5-Rotundone was used as an internal standard. The structure of the compound is reported in Fig. 4.5. 

Figure 5.1. HS (headspace)-SPME-GC/MS chromatogram recorded in the analysis of a Gewiirztraminer wine volatiles performed using a CAR-PDMS-DVB fiber and the experimental conditions reported in Table 5.1. (1) ethyl hexanoate (2) 2- and 3-methyl-1-butanol (isoamyl alcohols) (3) ethyl lactate (4) 1-hexanol (5) ethyl octanoate (6) 1-heptanol (internal standard) (7) benzaldehyde (8) linalool (9) ethyl decanoate (10) diethyl succinate (11) a-terpineol (12) 2-phenylethyl acetate (13) 2-phenylethanol (14) octanoic acid.

TABLE 5.2. Wine Volatiles Detectable by HS-SPME Using a CAR-PDMS-DVB Fiber and Their Principal m/z Signals"... 

SPME (PDMS, CW-DVB, PDMS-DVB, PA fibers) SPME (PDMS-DVB fibers)... 

SPME (PDMS, PA, CW-DVB fibers) MA-HS-SPME (PDMS, PA, CW-DVB, PDMS-DVB fibers)/LLE HS-SPME (PDMS, PDMS-DVB, CW-DVB fibers) automatic... 

Unless otherwise noted, PDMS/DVB fiber was used for sampling headspace volatile compounds. 

Figure 4 Effect of the addition of sodium chloride on signal intensity (immersion SPME, PDMS/DVB fiber).

Figure 5 Extraction of passion fruit flavor compounds using headspace SPME (PDMS/ DVB fiber).

Figure 7 Comparison of static headspace analysis with headspace SPME (PDMS/DVB fiber) dry apricot flavor (20 m X 0.18 mm I.D. DB WAX 0.3 (i,m film thickness).

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