Visual test and colorimetric determination of gold(III) with the use of indicator paper

A visual test method has been proposed for the evaluation of the gold content. It is based on the linear dependence between the length of the colored zone on an indicator paper and gold(III) concentration. Indicator paper was covered by a polymer film and was in contact with the solution tested along one edge during analysis. It was impregnated by 3-phenyl-2,6-dimercapto-1,4-thiopyrone or by precipitate of its complex with copper(II). Besides Cu(II) can be replaced by the Au(III) ion tested in the composition of this complex. The concentration ranges for Au(III) determination were equal to 0.02−2 mg·L−1 or 4−590 mg·L−1, respectively, in the presence of excess of the transition and noble metals. It was demonstrated the effectiveness of the dynamic preconcentration of Au(III) for the subsequent colorimetric determination on paper filter for the concentration range 0.005–0.3 mg·L−1 (DL 0.02 mg·L−1) by using a sample volume of 10 mL. The developed procedures were successfully utilized for the determination of gold in synthetic mixtures, in auriferous quartz (RSD < 5%), and in ore from Zyryanovsk’s mine (Kazakhstan) with RSD < 8%.