QUANTIFICATION OF THALLIUM IN ROCKS AND METEORITES BY GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

A procedure was developed for the quantification of thallium at the ultratrace level (ng g-1) in geological materials. The sample is dissolved in 3 M H2SO4 to which is added KI and K2HPO4. The thallium is then extracted as its iodo complex into methylisobutyl ketone (MIBK), leaving behind most of the iron. The remainder of the iron is removed from the organic layer by back-extraction into 3 M H2SO4. The added K2HPO4 enhances the extraction of thallium into the MIBK layer which is then analysed by graphite furnace atomic absorption spectrometry. The limit of detection (3-sigma) was about 2 ng g-1 in the original solid sample, though this could be reduced by further multiple loadings. Precision and accuracy were determined by analysis of the standard reference rocks G-1, W-1 and CAAS Sulphide Ore. The precision ranged from 3.03-10.5% depending on the thallium content of the rocks, and the relative error (accuracy) ranged from 2.1-6.7%.