Development of a Headspace-Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS) Method for t
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Development of a Headspace-Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS) Method for the Determination of Benzene in Soft Drinks Adriana Pavesi Arisseto & Eduardo Vicente & Regina Prado Zanes Furlani & Ana Luiza Duarte Pereira & Maria Cecília de Figueiredo Toledo
Received: 19 September 2012 / Accepted: 13 December 2012 # Springer Science+Business Media New York 2012
Abstract A method based on headspace-solid phase microextraction and gas chromatography with mass spectrometry has been developed and validated for the determination of benzene in soft drinks. The extraction step was optimized using a rotatable central composite design including the following experimental variables: extraction temperature, extraction time, sample weight, and salt concentration. The optimized procedure, which was carried out at 30 °C during 30 min by using a 75 μm carboxen-polydimethylsiloxane fiber, showed good linearity within the concentration range 0–25 μgkg−1 (r2 >0.999), mean recoveries from 97.5 to 103.1 %, and coefficients of variation from 1.5 to 13.4 % for repeatability and from 1.5 to 15.7 % for withinlaboratory reproducibility. Limits of detection and quantification were calculated at 0.02 and 0.08 μgkg−1, respectively. The method was applied to determine the concentrations of benzene in 77 samples of beverages from the Brazilian market. Levels from 99.9 %) and benzene-d6 (Aldrich, purity>99.9 %) were obtained from Sigma-Aldrich (SigmaAldrich Corp., St. Louis, MO, USA). Methanol was of HPLC-grade (Tedia Company Inc., Fairfield, OH, USA) and water was purified by reverse osmosis (Gehaka, São Paulo, SP, Brazil). Individual stock solutions of both standards at ca 2 mgmL−1 were prepared every 2 weeks by dissolving the compounds in methanol. For that, a 5-mL glass vial was filled with methanol and sealed, and the exact weight of methanol was recorded. The headspace in the vials might be kept as small as possible, in order to keep partitioning of benzene into the gas phase low. About 10 μL of the standard was injected in the vial through a silicone– PTFE septum with a syringe, holding the vial in an inverted position. The exact weight of added standard was recorded, and the concentration was expressed in milligrams per milliliter, taking into account the density of methanol. Intermediate (ca 4 μgmL−1, every week) and work solutions (ca 0.04 μgmL−1, daily) were prepared in water by using the same procedure described previously and taking appropriate volumes of stock and intermediate solutions, respectively. All solutions were stored at 4 °C. SPME Optimization Initial experiments were conducted with 1.0 g of an orangeflavored soft drink. Five types of fiber (CAR/PDMS 75 μm, DVB/CAR/PDMS 50/30 μm, PDMS/DVB 65 μm, PDMS 100 μm, and PDMS 30 μm) acquired from Supelco (Supelco, Bellefonte, PA, USA) were assessed in order to obtain the best sensitivity and selectivity for the extraction of benzene. The fibers were previously conditioned according to the manufacturer instructions and tested at two temperat
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