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

ABSTRACT

OBJECTIVE: To evaluate the capacity of national laboratories for determination of benzene in drinking water using Proficiency Testing Program. METHODS: The preparation methods 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. RESULTS: The total of 242 laboratories throughout the country participated in the Proficiency Testing Program. The total of 220 laboratories, or 90. 9% of total participating laboratories, obtained satisfactory results. Results provided by 9 laboratories, or 3. 7% of total participating laboratories, were found to suggest doubts in their capacities. Finally, there were 13 laboratories, constituting 5. 4% of total participating laboratories, with results that were found to be outliers. CONCLUSION: The capacity of national laboratories for determination of benzene 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.