Development of a triple spike methodology for validation of butyltin compounds speciation analysis by isotope dilution mass spectrometry : Part 2. Study of different extraction procedures for the determination of butyltin compounds in mussel tissue CRM 477

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Abstract
The triple spike GC-ICP-MS methodology developed in Part 1 of this paper has been applied here to study and validate different extraction procedures previously reported in the analytical literature for speciation analysis of biological materials in the determination of butyltin compounds. Microwave assisted extraction, mechanical shaking, alkaline hydrolysis with tetramethylammonium hydroxide (TMAH) and enzymatic digestion have been evaluated under different conditions for the determination of these species in mussel tissue CRM-477. The results obtained showed extensive degradation of the species using alkaline hydrolysis with TMAH and also a lack of isotope equilibration when using enzymatic digestion. The use of microwave assisted extraction with methanol–acetic acid showed the best results in terms of low degradation, rapid isotope equilibration and quantitative recoveries. Quantitative extraction was also obtained, however, by mechanical shaking at 37 °C using methanol–acetic acid as extractant, with no degradation of the species. The developed triple spike methodology was able to correct for as much as 50% degradation of DBT to form MBT during sample pre-treatment. Moreover, isotope equilibration studies performed using different extraction procedures have shown that the required complete isotope equilibration is achieved only after the naturally occurring organotin compounds are completely released to the solution from the solid matrix.