Determination of indium and tellurium in geological reference materials by solvent extraction and graphite-furnace AAS

A simple and sensitive method for the determination of In and Te in geological reference materials is presented. A sample of 0.01 to 1.0 g, containing less than 50 mug of Bi, Pb, or Sn, and 100 mug of Cu, was decomposed with aqua regia and HF. The contents were then evaporated to dryness. The residue was dissolved by heating with diluted HC1, and centrifuged to remove any undissolved material. After the addition of sulphamic acid, potassium iodide-ascorbic acid, and palladium solutions to the supernatant, In and Te were extracted into 0.5 similar to 1.0 mi of MIBK containing 5% trioctylmethylammonium chloride, and determined by graphite-furnace AAS. Although interference from most elements could be minimized by the addition of palladium as a matrix modifier, a large amount of Bi, Pb, Sn and Cu suppressed the In and/or Te absorbance. The relative standard deviation was smaller than 10% for a content larger than 3 ng of In and Te, and the limit of detection for both elements was 0.2 ng/g for a 1 g sample. This method was successfully applied to the determination of In and Te in various geological reference materials.