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

A method is presented for the simultaneous derivatisation and solid-phase m icroextraction (SPME) of organotin and organolead compounds in aqueous samp les or extracts, based on gas chromatographic separation and atomic emissio n detection (GC-AED). Derivatisation is carried out in situ in aqueous solu tion by sodium tetrapropylborate, which has only recently become commercial ly available. The use of the tetrapropylborate reagent allows the simultane ous derivatisation and determination of all environmentally relevant organo tin (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, sho wing that the derivatisation yield has an optimum at elevated temperature, while the extraction efficiency generally decreases with increasing tempera ture. 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 repeatab ility 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% withi n the calibrated range.