Determination of Se using a solid-phase micro-extraction device coupled to a graphite furnace and detection by gas chromatography-mass spectrometry Elidiane Gomes da Silva, a Fabio Augusto b and Marco Aur elio Zezzi Arruda * a Received 8th February 2012, Accepted 11th June 2012 DOI: 10.1039/c2an35598a A solid-phase micro-extraction (SPME) method using an SPME fiber device and graphite furnace (GF) for extracting Se compounds was proposed. Various factors affecting the derivatization and extraction of Se(IV) by SPME-GF were evaluated, including the effect of acid (type and concentration), the concentration of the derivatizing agent, the derivatization temperature, the extraction and derivatization times and the extraction temperature. After optimizing these conditions, the quantification of Se(IV) was performed by Gas Chromatography-Mass Spectrometry (GC-MS). The limit of detection was 0.37 mgL 1 for Se(IV). The method was successfully applied to the total Se determination in certified reference materials (BCR-414 and SRM 1643e). A recovery of 97% was obtained for water (SRM 1643e). After microwave oven decomposition and the reduction of selenium using a mixture of 2 mol L 1 HCl and 1% (w/v) KBr, a recovery of 101% and a relative standard deviation of 3.5% were attained for plankton (BCR-414). The SPME-GF method combined with GC- MS was also applied to the determination of the total selenium in a drug sample (selenium chelate). Introduction Graphite furnace atomic absorption spectrometry (GF AAS) not only provides good sensitivity but also improves the selectivity when analyzing complex samples. The increase in selectivity can be attributed to the accurate control of both time and tempera- ture as the standards and samples are heated. 1 It is well known that different species (from metallic to met- allo-biomolecules) possess different degrees of volatility. As a result, the capability of the graphite furnace (GF) in terms of temperature control could be taken into account not only to remove concomitant substances but also to promote the extrac- tion of different volatile species during the drying step of the temperature program. Gas chromatography is a technique that is currently used for the determination of volatile selenium species, such as dime- thylselenide, dimethyldiselenide and selenite after reaction with suitable derivatizing agents to form volatile compounds. 2–8 GC- MS coupled with solid-phase micro-extraction could provide a method with high sensitivity, accuracy and precision that is suitable for quantitative determinations 9 and speciation purposes. 4,10 Recently, Lopes et al. 11 proposed a new system in which an SPME fiber was coupled to GF aiming the speciation of orga- notin compounds (dibutyltin and tributyltin) with subsequent identification by GC-MS. The goal of the present work is to refine the derivatization and extraction procedure inside the GF and present applications of this new approach by the determination of Se(IV) using GC-MS. Experimental Reagents, solutions and apparatus Analytical-grade chemicals, including hydrochloric acid, nitric acid, hydrogen peroxide (Merck, Darmstadt – Germany) and potassium bromide (Carlo Erba, Milan – Italy), were used. A stock solution containing 1000 mgL 1 selenium was prepared by dissolving sodium selenite (Sigma-Aldrich, St Louis – MO, USA) into 0.2% (v/v) aqueous nitric acid. Working standard solutions of Se(IV) were prepared immediately prior to use by appropriate dilutions of the stock with water from a Milli-Q water purifica- tion system (Millipore, Bedford, USA). The derivatizing reagent 4,5-dichloro-1,2-phenylenediamine (DCPDA, 97% purity, Aldrich) was prepared in 0.1 mol L 1 hydrochloric acid, which had been previously diluted in ethanol. A DGT 100 Plus (Provecto Anal  ıtica, Brazil) microwave oven was used for sample decomposition. For the extractions, SPME fibers that were coated with 65 mm polydimethylsiloxane/ divinylbenzene (PDMS/DVB) were used (Supelco, Bellefonte – PA, USA). The fibers were conditioned prior to use according to the supplier’s recommendations. The desorption of the analytes a National Institute of Science and Technology for Bioanalytics and Spectrometry, Sample Preparation and Mechanization Group (GEPAM), Institute of Chemistry – University of Campinas (UNICAMP), P.O. Box 6154, 13083-970 Campinas, SP, Brazil. E-mail: zezzi@iqm.unicamp.br b Laboratory of Gas Chromatography, Institute of Chemistry – University of Campinas (UNICAMP), P.O. Box 6154, 13083-970 Campinas, SP, Brazil This journal is ª The Royal Society of Chemistry 2012 Analyst, 2012, 137, 3841–3846 | 3841 Dynamic Article Links C < Analyst Cite this: Analyst, 2012, 137, 3841 www.rsc.org/analyst PAPER Published on 12 June 2012. Downloaded by UNIVERSIDAD ESTADUAL DE CAMPINAS on 25/06/2013 13:52:08. View Article Online / Journal Homepage / Table of Contents for this issue