FLOW-INJECTION SAMPLE PREPARATION FOR ORGANOTIN SPECIATION ANALYSIS OF WATER BY CAPILLARY GAS-CHROMATOGRAPHY MICROWAVE-INDUCED PLASMA-ATOMIC EMISSION-SPECTROMETRY

A semi-automated flow-injection system was developed for on-line sample preparation for the determination of mono-, di- and tributyl- and -phenyltin compounds in water. The procedure is based on the preconcentration of ionic organotin compounds by sorption on bonded silica with octadecyl functional groups followed by on-column ethylation using sodium tetraethylborate. The derivatized species are eluted with 250 mul of methanol, separated by gas chromatography and detected with a microwave-induced plasma atomic emission detector. Aliquots of 25 mul of the eluate are introduced on to a capillary column using the cool injection technique. The solvent is vented off in the liner before the temperature of the latter is raised to release the analytes. A 10-50-ml water sample is sufficient for the analysis and a detection limit of 0.1 ng l-1 can be obtained. The developed procedure was applied to the determination of organotin compounds in a number of river water samples which were analysed in parallel using a manual liquid-liquid extraction procedure. The results agreed within 10-15% for concentrations of a few ng l-1.