Novel dissolution procedure using a mixture of manganese dioxide and hydrochloric acid for the matrix independent determination of gold

Abstract

A mixture of manganese dioxide and hydrochloric acid has been used for the accurate and precise determination of gold in various gold-bearing matrices. Results of intermethod comparison studies, F-test on variances, Mann-Whitney U-test, Spearman rank correlation and regression analyses are presented. The recommended method can be applied to a quality control programme and for the evaluation of reference materials. Various standard reference materials (SRM) of diverse matrices have been examined to check the validity of the method and the results were found to be in very good agreement with the certified data. Sample decomposition is straight forward [1-10 g sample (roasted at 600-700 degrees C) + 5 g of MnO2 + 30 mt of 2 mol/L HCl]. Gold is coprecipitated with potassium tellurite using tin (II) chloride solution. The precipitate is extracted into toluene and finally stripped back into aqua-regia solution for final nebulization into an air-acetylene flame for atomic absorption spectrophotometry. The method is very simple and easily adaptable, and more convenient than conventional methods involving aqua regia or a hydrobromic acid-bromine water mixture.