Evaluation of the Interlaboratory Comparison Results of the Chemical Composition of Copper Concentrates and Analysis of the Causes of Outliers

Abstract

BACKGROUND Composition analysis of copper concentrate is an important method to determine its quality, especially the analysis of the main element copper. Currently, the main analytical methods for the determination of copper content in copper concentrate include iodometry, inductively coupled plasma-optical emission spectrometry (ICP-OES), flame atomic absorption spectrometry (FAAS), X-ray fluorescence spectrometry (XRF), and electrolytic gravimetric methods. OBJECTIVES To ensure the uniformity, accuracy, and reliability of the standard values, interlaboratory comparison activities for the determination of copper, magnesium, lead, and zinc in copper concentrate were organized. METHODS Through the statistical analysis of the test results of the participating laboratories, the technical level and ability of the participating laboratories in the determination of copper, magnesium, lead, and zinc in copper concentrates were evaluated. RESULTS The results showed that most laboratory results were satisfactory, the satisfaction rate of copper in the copper concentrate was 92.9%, and the average satisfaction rate of copper, magnesium, lead, and zinc was 89.0%. The outliers in a few laboratories were mainly attributed to sample pretreatment, lack of understanding and mastering of the analytical methods by the testing personnel, and other related factors, such as the instrument status. CONCLUSIONS Because of incomplete sample decomposition, the alkali leaching method could not be used for pretreatment of copper concentrate. Additionally, the alkali fusion method is not recommended for copper concentrate pretreatment because of its complicated process and matrix interference. Acid dissolution titration is preferred as a pretreatment method for the determination of copper in the copper concentrate. The acid-dissolution ICP-OES method for simultaneous determination of Cu, Mg, Pb, and Zn in the copper concentrate is efficient and rapid with satisfactory results. However, further experiments are required to investigate their stabilities.

Keywords

• copper concentrate
• interlaboratory comparison
• proficiency testing
• outlier
• acid dissolution
• iodometry