Grignard Derivatization and Mass Spectrometry as Techniques for the Analysis of Butyltins in Environmental Samples

Abstract

When analyzing environmental samples for tributyltin (TBT) and its breakdown products, it is important to speciate the various organotins that may be present in the samples. Most commonly used methods require a derivatization step to form volatile organotin hydrides or tetraalkyltin derivatives. The tetraalkyltins formed by reaction with Grignard reagents are stable compounds that are readily separated by gas chromatography and produce characteristic mass spectra that are easily interpreted. Various types of Grignard reagents and solvents have been used in the published methods for the analysis of TBT in environmental samples. When the longer chain (pentyl and hexyl) derivatives are formed, sample extracts can be concentrated to small volumes without significant losses from volatilization.

Gas chromatography with modified flame photometric detection has been shown to be a sensitive and somewhat selective technique for quantifying butyltins. However, the complexity of environmental extracts means that the only way to identify butyltins positively is with mass spectrometry. Gas chromatography-mass spectrometry, in combination with either electron ionization or positive chemical ionization, has been the most commonly used method. Qualitative identification of butyltins has usually been accomplished by full scanning and is facilitated by the characteristic isotopic pattern displayed by tin (10 stable isotopes). Selected ion monitoring has been the technique used most often for quantification by mass spectrometry. Mass spectrometry-mass spectrometry, alternative ionization methods, and stable isotope monitoring are all techniques that have also been applied to the analysis of butyltins by mass spectrometry.