Ultratrace speciation analysis of organolead in water by gas chromatography-atomic emission spectrometry after in-liner preconcentration
Résumé
A rapid and sensitive method for the speciation of organolead compounds in water at the sub-ng dm-3 level by gas chromatography-atomic emission spectrometry was developed. Only 100 cm3 of the sample are sufficient for the analysis and no preconcentration step by evaporation is necessary prior to the injection of the sample solution into the system. Sample preparation involves extraction of dithiocarbamate complexes of ionic organolead species into hexane followed by their propylation using a Grignard reaction. A 25 mm3 volume of the derivatized extract is injected on to a Tenax-packed liner. Before rapid, linear heating of the liner, the solvent is purged away at room temperature by a stream of helium while the analytes are trapped on the sorbent. The organolead compounds are separated on a capillary column and detected by an atomic emission detector. A detection limit of 0.1 ng dm-3 (as Pb) can be obtained. The precision of the method is 5% at the 1 ng dm-3 level with 90% recovery. Examples of analyses of tap water and polar snow are shown.