Spectrophotometric determination of tungsten based on molybdotungsten isopolyanions in presence of non-ionic surfactant

Simple and sensitive method was developed for the spectrophotometric determination of tungsten. The method was based on the formation of the colour associate of molybdotungsten isopolyanion (IPA) with organic dye malachite green and solubilization in the solution of non-ionic surface-active substance (SAS). Recommended procedure permits tungsten determination in the linear range 10−6 to 10−5 mol l−1 with ε=7.1×104 mol−1 l cm−1. More than 100-fold excess of molybdenum do not interfere. The proposed method was applied to the determination of tungsten in cobalt-molybdenum catalyst and in stainless steel with satisfactory results.