Determination of Polychlorinated Biphenyls in Solid Samples by Isotope Dilution Mass Spectrometry Using ³⁷Cl-Labeled...

This work describes the first application of (37)Cl-labeled compounds to isotope dilution mass spectrometry (IDMS). The synthesis of 12 (37)Cl-labeled polychlorinated biphenyls (PCBs) was carried out by the chlorination of biphenyl with isotopically enriched chlorine gas, generated by the direct oxidation of Na(37)Cl with potassium peroxymonosulfate. After an exhaustive purification due to the presence of other congeners, the concentration and the isotopic enrichment of all (37)Cl-labeled PCBs in the mixture was determined. The proposed procedure allows the simultaneous quantification of every isotope diluted PCB congener in a single gas chromatography-tandem mass spectrometry (GC-MS/MS) injection without resorting to a methodological calibration graph. The results obtained here demonstrate that the use of (37)Cl-labeled analogues provides results in agreement with the certified values of three different Certified Reference Materials (marine sediment SRM 1944, fish tissue 1947, and loamy soil CRM 962-50) and analytical figures of merit comparable to those obtained using regular IDMS procedures based on the use of commercially available (13)C-labeled analogues.