Determination of Gold in Jewellery Alloys via Potentiometric Titration. Procedure Standardization and Results Benchmarking

摘要

The present experimental work concerns the analytical determination of gold in jewellery alloys by means of potentiometric titration. In this contribution we focus on the practical aspects of this topic, in order to define a suitable procedure to be applied on real business applications. Therefore, instead of house-built electrodes as investigated before, the use of commercially available ones (Mettler-Toledo DS500 and DS800) is preferred. After a careful evaluation of experimental parameters such as pH, temperature, chloride and nitrate content, solution concentration, cleaning procedure, an optimised operating procedure has been developed, assuring the reproducibility of the method as well as the optimal electrode working-life. Finally, the efficacy and suitability of the method to cope with a plethora of different types of jewellery alloys and items have been tested comparing the results of the potentiometric titration carried out in three separate laboratories with the data obtained from fire assay. The consistency of these results supports the capability of the present method to constitute a robust and affordable alternative method to the classical fire assay.