[Proficiency test for determination of chlorate in drinking water].

To evaluate the capacity of national laboratories for determination of chlorate in drinking water using Proficiency Testing Program. The preparation method of the Secondary Standard Materials were used as the reference for the sample preparation in this Proficiency Testing Program. The homogeneity and stability of the samples and short-term stability for simulated transportation were tested by Single Factor Analysis of Variance(ANOVA) and Linear Regression and Mean consistency test. The result provided by participant laboratories were analyzed by robust statistics and assessed using the Z-score. A total of 327 laboratories throughout the country participated in the Proficiency Testing Program. 307 laboratories, or 93. 9% of total participating laboratories, obtained satisfactory result. Results provided by 5 laboratories, or 1. 5% of total participating laboratories, were found to suggest doubts in their capacities. Finally, there were 15 laboratories, constituting 4. 6% of total participating laboratories, with result that were found to be outliers. The capacity of national laboratories for determination of chlorate in drinking water has been ranked as satisfactory according to statistical analysis of the Proficiency Testing Program result. Only a small portion of the participants require further improvement in their capacities.