Optimization of Soxtec extraction procedure for determination of polybrominated diphenyl ethers in bivalve mollusc

Abstract

A comprehensive and efficient method is presented for the determination of 9 polybrominated diphenyl ether congeners (PBDEs), 2,4,4′-tribromodiphenyl ether (PBDE-28), 2,3′,4,4′-tetrabromodiphenyl ether (PBDE-47), 2,2′,4,4′,6-pentabromodiphenyl ether (PBDE-66), 2,2′,4,4′,5-pentabromodiphenyl ether (PBDE-100), 2,2′,3,4,4′-pentabromodiphenyl ether (PBDE-99), 2,2′,4,4′,5,6′-hexabromodiphenyl ether (PBDE-85), 2,2′,4,4′,5,5′-hexabromodiphenyl ether (PBDE-154), 2,2′,4,4′,5,5′-hexabromodiphenyl ether (PBDE-153) and 2,2′,3,4,4′,5,6′-heptabromodiphenyl ether (PBDE-183), in mollusc bivalve samples. An experimental design was used to evaluate the influence of several operational parameters on the extraction performance and to obtain the best experimental conditions. Under the final working conditions, freeze-dried mollusc was placed in the Soxtec thimble in order to extract PBDEs with 100 mL of n-hexane-acetone (4: 1) after 1.5 h and 1 h of boiling and rinsing times, respectively. Soxtec extracts were additionally purified on a multilayered column and after injected in the gas chromatography combined with mass spectrometry (GC-MS) system. Quantitative recoveries of the analytes at three concentration levels ranged between 80 and 108%, and limits of quantification of the method (LOQs) between 0.5 and 20 ng/g. Analysis of mussel and clam samples showed that PBDE-47 and PBDE-99 were presented in almost all samples with concentrations between 0.6 and 2.6 ng/g dry weight. Moreover, a certified reference material (NIST 2974a) was used. The obtained concentrations were in agreement with the certified values.