Determination of ionic alkyllead compounds in water, soil and sediment by high-performance liquid chromatography-quartz tube atomic absorption spectrometry

Abstract

A thermospray-microatomiser assembly was used to interface directly a high-performance liquid chromatographic (HPLC) column with a quartz T-tube mounted within the optical beam of an atomic absorption spectrometer. The system was then optimised for the detection of lead-containing analytes in column eluate. By physically separating the transfer line tip of the thermospray unit from the entry port for oxygen in the microatomiser, a controlled pyrolysis of HPLC eluate was achieved that was compatible with mobile phases containing up to 50% water. The atomisation appeared to be a flame (T= 1400–1600 °C) mediated process which was supported by chromatographic eluate (fuel) and oxygen. Four ionic alkylleads (R₃Pb⁺, R₂Pb²⁺; R = CH₃, C₂H₅) were separated efficiently on a Nucleosil C₁₈ column using methanol-water (3 + 1 V/V) containing 600 µg ml^–1 of ammonium tetramethylenedithiocarbamate. Methods for the determination of these analytes in water, anoxic sediment and sandy clay loam by complexometric extraction, solvent-solvent partition and chromatographic analysis were optimised. The recoveries for each of these analytes (added at 10 ng g^–1) were 72% from each of these matrices and the limits of detection ranged from 1 to 2 ng. Hence sub-ng g^–1 alkyllead determinations for 10 g of these matrices are feasible and there is no need for derivatisation of the analyte.