A methodology for speciation of methyltins in mammalian tissues

Exposure to methyltin compounds results in morphologically detectable damage to several mammalian organ systems. Although reliable dose-response relationships have been described, a fast method for quantitating levels of various methyltin species in target organs has been unavailable. It has been possible to measure organotins as total tin using atomic absorption spectrometry, but speciation of methyltins has proved difficult. We present a rapid method for quantitative analysis and speciation of methyltins, direct from mammalian tissues. Methyltin compounds (monomethyltin trichloride, dimethyltin dichloride, trimethyltin chloride, and tetramethyltin) are purged from freshly homogenized mouse kidney and brain tissues using NaBH4. The volatile organotin hydrides produced are cryogenically trapped on the head of a gas chromatographic column (at -40 degrees C) and eluted using a linear temperature program (15 degrees C/min to 190 degrees C). The compounds are detected using selected ion monitoring in a Hewlett Packard 5985-B mass spectrometer. Quantitation is achieved by integration of the areas of the chromatographic peaks. Linear response is obtained over the range of 1 ng to 30 micrograms for each compound. Recoveries of methyltins spiked into tissues are greater than 85%.