Abstract

A proficiency testing scheme (CNAS PT0038-PT-201802) for the determination of hexavalent chromium in leather was organised in China. The test materials were prepared by adding a tanning agent containing hexavalent chromium to a blank sheepskin during the retanning process. The retanning was identical to the real production process to assure the representation of the test materials. Homogeneity and stability indicated that the test materials were suitable for the proficiency testing samples. The assigned values of test materials for proficiency assessment were derived directly from the reported results of laboratories, and the measurement performance for determining hexavalent chromium in leather were assessed using robust z-scores. This PT program is necessary and useful to help the laboratories to comply with quality assurance requirements and improve the detection level.