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

To evaluate the capacity of national laboratories for determination of fluoride 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 were tested by single factor analysis of variance( ANOVA) and linear regression. The results provided by participant laboratories were analyzed by robust statistics and assessed using the Z-score. A total of 985 laboratories throughout the country participated in the proficiency testing program. 910 laboratories, or92. 4% of total participating laboratories, obtained satisfactory result. Results provided by26 laboratories, or 2. 6% of total participating laboratories, were found to suggest doubts in their capacities. Finally, there were 49 laboratories, constituting 5. 0% of total participating laboratories, with results that were found to be outliers. The capacity of national laboratories for determination of fluoride in drinking water has been ranked as satisfactory according to statistical analysis of the proficiency testing program results. Only a small portion of the participants require further improvement in their capacities.