Development and application of an ultratrace method for speciation of organotin compounds in cryogenically archived and homogenized biological materials
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An accurate, ultra-sensitive and robust method for speciation of mono, di, and tributyltin (MBT, DBT, and TBT) by speciated isotope-dilution gas chromatography–inductively coupled plasma-mass spectrometry (SID-GC–ICPMS) has been developed for quantification of butyltin concentrations in cryogenic biological materials maintained in an uninterrupted cryo-chain from storage conditions through homogenization and bottling. The method significantly reduces the detection limits, to the low pg g−1 level (as Sn), and was validated by using the European reference material (ERM) CE477, mussel tissue, produced by the Institute for Reference Materials and Measurements. It was applied to three different cryogenic biological materials—a fresh-frozen mussel tissue (SRM 1974b) together with complex materials, a protein-rich material (whale liver control material, QC03LH03), and a lipid-rich material (whale blubber, SRM 1945) containing up to 72% lipids. The commutability between frozen and freeze-dried materials with regard to spike equilibration/interaction, extraction efficiency, and the absence of detectable transformations was carefully investigated by applying complementary methods and by varying extraction conditions and spiking strategies. The inter-method results enabled assignment of reference concentrations of butyltins in cryogenic SRMs and control materials for the first time. The reference concentrations of MBT, DBT, and TBT in SRM 1974b were 0.92 ± 0.06, 2.7 ± 0.4, and 6.58 ± 0.19 ng g−1 as Sn (wet-mass), respectively; in SRM 1945 they were 0.38 ± 0.06, 1.19 ± 0.26, and 3.55 ± 0.44 ng g−1, respectively, as Sn (wet-mass). In QC03LH03, DBT and TBT concentrations were 30.0 ± 2.7 and 2.26 ± 0.38 ng g−1 as Sn (wet-mass). The concentration range of butyltins in these materials is one to three orders of magnitude lower than in ERM CE477. This study demonstrated that cryogenically processed and stored biological materials are a promising alternative to conventional freeze-dried materials for organotin speciation analysis, because these are, at present, the best conditions for minimizing degradation of thermolabile species and for long-term archival. Finally, the potential of the analytical method was illustrated by analysis of polar bear (Ursus maritimus) and beluga whale (Delphinapterus leuca) liver samples that had been collected in the Arctic and archived at the Marine Environmental Specimen Bank. Significant concentrations of butyltin compounds were found in the samples and provide the first evidence of the presence of this class of contaminant in the Arctic marine ecosystem.
KeywordsSpeciation Tributyltin ICPMS Isotope dilution Specimen bank Standard reference material (SRM)
The authors acknowledge LGC Ltd (Teddington, UK) for providing the enriched TBT and DBT standard as part of an international intercomparison exercise. The development of the marine mammal SRMs and control materials and the Marine ESB samples used in this paper involved numerous individuals and organizations including the National Marine Fisheries Service’s Marine Mammal Health and Stranding Response Program, New England Aquarium, Wayne McFee of the National Oceanic and Atmospheric Administration, U.S. Geological Survey’s Alaska Science Center, North Slope Borough Department of Wildlife Management, and Todd O’Hara of the University of Alaska Fairbanks.
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