Determination of priority polybrominated diphenyl ethers by isotope dilution gas chromatography(electron ionization)MS using 81Br-labeled standards

A mixture of (81)Br-labeled polybrominated diphenyl ethers (PBDEs), previously synthesized in our laboratory, was separated by liquid chromatography for the individual isolation of different (81)Br-labeled PBDEs containing from 3 to 6 bromine atoms. The different fractions were collected, and a mixed labeled standard was then prepared adequate for the determination of priority PBDEs (congeners 28, 47, 99, 100, 153, and 154) in environmental samples. The spike mixture was then characterized using gas chromatography(electron ionization)MS (GC(EI)MS) both in isotope composition and concentration in combination with multiple least-squares. Contamination from natural abundance BDEs 153 and 154 was detected in the spike mixture, and a new isotope dilution equation was developed to take into account the natural abundance contribution from the spike. The spike mixture was shown to be stable during at least 4 months, and no isotope exchange between natural abundance and labeled PBDEs was detected during this period of time. Finally, the (81)Br-labeled PBDEs standard was used for the determination of congeners 28 (+33), 47, 49, 99, 100, 153, and 154 in a standard reference material (Lake Michigan fish tissue SRM 1947) using three different sample to spike ratios. No methodological calibration needed to be prepared, as no isotopic effects were detected using this labeling mode. Concentrations found were in agreement with the certified concentrations (recoveries between 89% and 116%), and reproducibility was always below 7% RSD. Kragten procedure was used to calculate expanded uncertainties. Very low limits of detection were obtained for all compounds (between 0.02 and 0.9 ng·g(-1)) using the procedure developed here.