NOVEL DISSOLUTION PROCEDURE USING A MIXTURE OF MANGANESE-DIOXIDE AND HYDROCHLORIC-ACID FOR THE MATRIX INDEPENDENT DETERMINATION OF GOLD

A mixture of manganese dioxide and hydrochloric acid has been used for the accurate and precise determination of gold in various gold-bearin g matrices. Results of intermethod comparison studies, F-test on varia nces, Mann-Whitney U-test, Spearman rank correlation and regression an alyses are presented. The recommended method can be applied to a quali ty control programme and for the evaluation of reference materials. Va rious standard reference materials (SRM) of diverse matrices have been examined to check the validity of the method and the results were fou nd to be in very good agreement with the certified data. Sample decomp osition 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 s olution for final nebulization into an air-acetylene flame for atomic absorption spectrophotometry. The method is very simple and easily ada ptable, and more convenient than conventional methods involving aqua r egia or a hydrobromic acid-bromine water mixture.