Determination of Sn- and Pb-organic compounds by solid-phase microextraction-gas chromatography-atomic emission detection (SPME-GC-AED) after in situ propylation with sodium tetrapropylborate

A method is presented for the simultaneous derivatisation and solid-phase microextraction (SPME) of organotin and organolead compounds in aqueous samples or extracts, based on gas chromatographic separation and atomic emission detection (GC-AED). Derivatisation is carried out in situ in aqueous solution by sodium tetrapropylborate, which has only recently become commercially available. The use of the tetrapropylborate reagent allows the simultaneous derivatisation and determination of all environmentally relevant organotin (butyl- and phenyltin) and organolead (methyl- and ethyllead) compounds. Optimum reaction and extraction conditions are established. The effect of temperature on the combined derivatisation/extraction step is studied, showing that the derivatisation yield has an optimum at elevated temperature, while the extraction efficiency generally decreases with increasing temperature. For practical reasons, it was decided to carry out the determination at room temperature with a reaction/extraction time of 20 min. Under these conditions, detection limits in the range of 0.2 ng l(-1) (as metal) could be achieved with headspace sampling and a 20 ml sample volume. The repeatability of measurements in the low ng l(-1) range is between 2 and 9% and the relative standard deviation of the method is generally lower than 5% within the calibrated range.