Proficiency testing programs to improve traceability in chemical analysis

The results of the proficiency test program T062 organised by CNACL (China National Accreditation Committee for Laboratories) were analysed with different statistical procedures: the robust statistic procedure used by the proficiency test organisers and the UNI ISO 5725-2 [8] procedure which is a basic method for the determination of the repeatability and the reproducibility of a standard measurement method to improve the traceability in chemical analysis.The data are taken from a program of chemical analysis on a low alloy steel.The obtained results are commented; the paper aim to give elements of discussion about standard test method, uncertainty evaluations, and repeatability of test results on chemical analysis performed by chemical laboratories.