Sample pretreatment for voltammetric determination of Pd - selective separation and preconcentration using Cellex-T

Abstract

Constant increase of the content of platinum group elements in the environment creates the need for their analysis in natural samples. Especially determination of palladium is challenging: it occurs at ultra-trace levels, analytical techniques offer too high limits of detection and interferences from sample matrix limit the application of some analytical methods. The aim of this work was to propose a complete methodology of Pd determination, with special attention paid to establishing the conditions for efficient decomposition of thiourea. The analysis was performed using ICP MS and/or voltammetry in samples naturally containing traces of Pd. The procedure includes sample digestion in aqua regia, separation of Pd from a complex natural matrix simultaneously with its 10-fold preconcentration (SPE) on anion-exchanger Cellex-T (Pd elution with 0.10 mol L−1 TU in 0.10 mol L−1 HCl). Voltammetric determination of Pd is possible after mineralization of thiourea in conc. nitric acid or the mixture of nitric and perchloric acids. The recovery is very satisfying, reaching more than 90%. The proposed methodology can be applied for quartz sand samples containing at least 2 ppb Pd.