Continuous Determination of Gold and Silver in Geochemical Samples by Atomic Absorption Spectrometry Concentrated by Load Diphenylthiourea Foam

The results of analysis by the traditional methods of gold and silver determination in geochemical samples by emission spectrometry, chemical spectroscopy or atomic absorption spectrometry concentrated by load foam, is unstable and inefficient. As reported in this paper, the samples have been decomposed by 50% aqua regia. Au and Ag were concentrated by loaded diphenylthiourea foam which was cleaned with deionized water. The trace amounts of Au and Ag were then simultaneously measured by using Graphite Furnace Atomic Absorption Spectrophotometry(GFAAS) and Flame Atomic Absorption Spectrophotometry (FAAS). The experimental conditions were optimized by using a concentration of diphenylthiourea of 7 mg/mL, hydrochloric acid concentration of 8%, oscillation time of 25 min and absorption temperature of 20℃. The recoveries of Au and Ag were 97.9% and 98.8% respectively. After the improvement, the detection limits of Au and Ag were 0.25 ng/g and 0.038 μg/g respectively, relative errors were 2.0%-14.0% and 7.7%-13.3% (n=9), RSDs were 3.1%-12.4% and 5.1%-13.2% respectively (n=9) by using this method. The method has been verified by determination of national first level standard material with satisfactory results. This method resolves simultaneous determination of Au and Ag in one solution. Compared with determination of Ag by Emission Spectrometry and determination of Au by Graphite Furnace Atomic Absorption Spectrometry, this method has the advantages of large sampling of 10 g to increase the representativeness, simple operation, low cost and labor, high accuracy and precision, which was able to efficiently test trace Au and Ag.