Method for the purification of polybrominated diphenyl ethers in sediment for compound-specific isotope analysis

A purification method for lower polybrominated diphenyl ethers (PBDEs, from tri- to hexa-BDE) in sediment for compound-specific isotope analysis (CSIA) was developed in this study. The compounds were extracted using a Soxhlet apparatus with addition of activated alumina and Florisil in the paper tube during the Soxhlet extraction provided for less complex extracts. Then, the extract was isolated from polar compounds using a multi-layer silica gel column, separated into different fractions using alumina/silica (Al/Si) gel columns and finally purified using a Florisil column. The mean recoveries of the major PBDE congeners in the spiked samples ranged from 76.2% to 82.4%. The purity of the samples was verified by GC–MS in full scan mode. The stable isotopic integrity of the spiked samples after the purification was tested by comparing the stable carbon isotope ratios (δ13C) of the processed and the unprocessed standard materials. The differences in the δ13C values for each compound between the processed and unprocessed standards were less than 0.5‰, with the exception of BDE100 (0.54‰). Finally, the purification and isotope analysis method was successfully applied to measure the δ13C of PBDEs in sediments. This application of the method indicated that CSIA seems to be a promising method for providing intrinsic characteristics for further environmental fate studies of PBDEs.