Determination of low concentrations of tungsten and molybdenum in geological materials using inductively coupled plasma atomic emission spectrometry with pre-concentration on activated charcoal

Abstract

A practical and efficient method is described for the determination of W and Mo at concentrations of 0.5–100 µg g^–1 in geological materials. The sample is first decomposed by alkaline fusion with sodium carbonate-sodium nitrate and the melt is leached with water to solubilise the elements as their oxy-anions. Concentration and separation of the analytes are achieved by selective adsorption of their 8-hydroxyquinolinates on to activated charcoal, which is then ashed and the metals solubilised. The acidic solution is analysed by inductively coupled plasma atomic emission spectrometry. The application of this method to determine levels as low as 0.4 µg g^–1 of W and 0.2 µg g^–1 of Mo is demonstrated by the analysis of 22 international reference materials.