Effect of hydrogen bromide doping on capillary gas chromatographic analysis of tributyltin and triphenyltin halides

Abstract

Tributyltin (TBuT) and triphenyltin (TPhT) compounds have been used as effective antifoulants in the marine environment. Trace levels of the trisubstituted tin halides (chloride and bromide) were separated unsatisfactorily on a capillary GC column (without any treatment). The halides, especially TPhT halides, are very polar, and when injected onto a GC column, most are adsorbed on the active sites on the column surface and do not elute smoothly from the column. In this paper, an apolar capillary GC column with flame photometric detection was used to investigate the direct GC analysis of TBuT and TPhT halides. Spiking of the column used was carried out by doping 1 µl of dilute methanolic HBr solution into the GC system prior to the injection of a standard or sample solution. Under the acidic conditions of doping, the peaks of TBuT and TPhT appeared. HBr doping was effective and showed excellent results; sharper and more symmetrical peaks and larger peak areas could be obtained by increasing the HBr concentration. Using a DB-1 capillary column and doping with HBr, trace levels of TBuT and TPhT halides were determined efficiently. Tripentyltin halide was used as an internal standard. Calibration graphs for TBuT and TPhT halides were linear in the range 0.1–0.6 µg ml^–1. Chlorides and bromides showed almost identical results. The mechanism of halide elution and peak sharpening by acid doping and the resulting halogen exchange reaction during GC analysis is considered from a chromatographic viewpoint.