Precision of Electrorefined Copper Assaying

Abstract

A principal measure of the quality of electrorefined copper cathodes is impurity content. As such, good analytical precision is needed to identify subtle improvements in quality and to ensure that industry specifications are being satisfied. The object of this study was to determine and document the current state of refined copper analytical precision. Three levels of precision were evaluated. The highest level was determined from the sequential analyses of over 100 wire rod samples. The implications of this precision on both impurity specifications and actual content in cathodes are discussed. The study of the day-to-day precision and long-term precision among several laboratories was determined from analyses made on standard samples. A statistical comparison of the long-term and sequential data is given. Based on the data presented in this paper, two areas of refined copper assaying which require improvement are evident: (1) precision of long-term interlaboratory analyses of many elements and (2) detection limits for others. If appropriate analytical accuracies and precisions are to be achieved, substantial progress in analytical methodology will be required.