Determination of vanadium in steels and geological materials by liquid-liquid extraction and graphite furnace atomic absorption spectrometry

Abstract

A procedure for determining vanadium in steels and geological materials involves dissolving the samples in concentrated HNO 3 for steels and iron-rich meteorites or in HClO 4-HF-HNO 3 (1:1:1) for siliceous materials. The solutions are evaporated to dryness and the residue is dissolved in 6 M HCl. The solutions are oxidized with K 2S 2O 8 and KMnO 4 at 70°C prior to separation of iron, chromium and molybdenum by extraction into isobutyl methyl ketone. After separation, the aqueous solution is reoxidized with KMnO 4 at 70°C. The residual solution containing vanadium and nickel is evaporated to dryness, the residue dissolved in 6 M HNO 3 and the vanadium extracted into tributyl phosphate, leaving the nickel behind. This purified extract is back-extracted into 2% H 2O 2 in 6 M HNO 3. The aqueous back-extract is analysed for vanadium by graphite furnace atomic absorption spectrometry. The limit of detection is about 0.3 μg V g −1 in the original sample. The relative standard deviation of the method was 3.7% for seventeen replicates of the NBS SRM 361 standard steel, with a relative error of 4.5%. Replicate analyses of standard silicate rocks (CAAS SY-1 anal SU-1) gave similar good precision and accuracy. Vanadium was determined in several iron meteorites and in the carbonaceous chondrite Allende.