Investigating the potential of high-performance liquid chromatography withatmospheric pressure chemical ionization-mass spectrometry as an alternative method for the speciation analysis of organotin compounds

Liquid chromatography with atmospheric pressure chemical ionization-mass sp ectrometry (LC-APCI-MS) was applied for the determination of butyl- and phe nyltin compounds. Chromatography was performed on a 30 x 2 mm, 3 mu m C18 c olumn, enabling the separation of mono-, di- and trisubstituted butyl- and phenyltin compounds in less than 10 min using a water/1% trifluoroacetic ac id/ methanol gradient. While satisfactory retention and resolution is achie ved for the di- and trisubstituted butyl- and phenyltin compounds, monobuty ltin and monophenyltin cannot be resolved chromatographically. Depending on the parameter values of the interface, APCI-MS detection allows both speci fic detection of the molecular ion or cluster ion at low to intermediate fr agmentor voltages or quasi-element specific detection of the Sn+ ion releas ed from the organotin compounds at high fragmentor voltages. The sensitivit y of MS detection is similar for butyl- and phenyltin compounds, but varies largely from monoto trisubstituted organotin compounds with tributyl- and triphenyltin being the most sensitively detectable compounds. Detection lim its are in the 20-65 pg tabs.) range in SIM mode and in the 750-2000 pg tab s.) range in the scan mode for tributyl- and triphenyltin and for dibutyl- and diphenyltin, respectively. Monobutyl- and monophenyltin can be detected with much lower sensitivity which, together with their unfavorable chromat ographic behavior, accounts for the fact that they cannot be analyzed at en vironmentally relevant concentrations. Although LC-APCI-MS is generally les s sensitive than comparable GC methods, it is applicable to the analysis of environmental samples as demonstrated by the analysis of the PACS-2 sedime nt certified reference material. Although the derivatization of the ionic o rganotin compounds, which particularly in real samples is a potential soure r of error, is circumvented when LC-APCI-MS is used, the extraction step is still critical and may lead to underestimation when quantitation is not do ne by the method of standard addition.