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SummaryExtra-fine powdered activated charcoal has been used as stationary phase (coating layer) in solid-phase microextraction (SPME). The efficiency and reliability of the prepared device have been investigated for the extraction of some volatile organic compounds such as benzene, toluene, ethylbenzene and xylene isomers (BTEX) from the headspace of water samples. Monitoring of the extracted compounds and further quantitative analysis of the real samples have been performed by capillary GC-FID. Effects of several factors such as temperature, addition of salt, and stirring speed on extraction efficiency and exposure time have been studied. Under optimum conditions, extraction recoveries for these compounds from 50 mL water were > 95 %. The calibration graphs were linear in the range 5 to 104 pg mL -1 and the detection limit for each BTEX compound was 1.5-2 pg mL -1. The results obtained by use of this porous layer activated charcoal (PLAC)-coated fiber have also been compared with results reported in the literature by use of a polydimethylsiloxane (PDMS)-coated fiber.

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KeyWordsGas ch ro matog rap hy Solid-phase microext faction Zincwire New fi bets Thiophenol and thiol compounds SummaryThe effTciency of anodTzed zinc wire as a new fiber forsolid-phase mTcroextractTon (SPME) has been investigated. Zinc wire was anodTzed by use of dTrect current in a solution of sodium hydroxide at room temperature. The fibers were used for the extractTon of thiophenol, as an example ofthTol compounds, from gaseous samples and from the headspace aqueous samples. The extracted analytes were transferred to a GC injector by use of an (Tn-house-desTgned) SPME syrTnge, whTch enabled easy changTng of SPME fibers. The results obtained prove the suitability of anodized zinc wire as a new fiber for extraction and sampling of some organic compounds from these samples. This behavior is most probably because of the porous layer of zinc oxide formed on the metal surface. In this work the optimum conditions were determined for preparation and conditioning of the fibers and extraction of the analytes. Under the opti mum conditions one fiberwas used for several identical analyses and relative standard devia tions (RSD) were below 3% (n -6). For fiberto fiber reproducibility RSD was 3.77% (n -6). The fiber is sturdy, inexpensTve, and durable, and can be prepared sTmpl,~ IntroductionOver the past ten years solid-phase microextraction (SPME) has become an attractive alternative to most conventional sampiing techniques and has gained widespread acceptance in many areas [1 5]. This technique integrates easy, rapid, sensitive, and safe sampling, extraction, and concentration with the sample introduction procedure used for GC and HPLC into a single step. SPME uses a small (1 cm) piece of fused silica, on which a liquid phase, similar to a GC stationary phase, has been coated to absorb or adsorb the analytes [5] [28], and Nafion are specialized phases for removal of species such as metal ions, proteins, polar compounds, etc. In recent years research has been directed to the application of new fibers to increase the selectivity, sensitivity, and durability of solid phases. In previous work we developed new fibers consisting of activated charcoal [29,30], anodized aluminum [31], and modified copper wires [32]. These fibers resulted in improvement of one or more of cost, durability, sensitivity, and range of application.Zinc oxide is an interesting metal oxide which can be produced easily. It has considerable adsorptive and catalytic behavior. Zinc oxide catalyses the hydrogenation of carbon dioxide [33] and carboxylic acids [34] to methanol and aldehydes, respectively, and the dehydrogenation of alcohols to aldehydes [35]. In this study a simple and rapid method for preparation of a new fiber consisting of zinc wire coated with zinc oxide (anodized zinc) has been investigated. Because of the considerable adsorptive capacity of ZnO, this wire can be used as an SPME fiber. This should ensure long life, low cost, and desirable selective adsorptive properties for SPME of some organic compounds.Original

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