[Interlaboratory comparison for determination of lead in drinking water]

To analyze and evaluate the testing capability of lead in drinking water in the laboratories of the provincial and municipal centers for disease control and prevention across the country by implementing the interlaboratory comparison project.

The preparation method of the secondary standard materials were used as the reference for the sample preparation in the interlaboratory comparison project. The homogeneity and stability of the samples and short-term stability for simulated transportation were tested by single factor analysis of variance(ANOVA) and mean consistency test(t test). On top of using the kernel density estimation to test the distribution of laboratory test result, we adopted a robust statistical method to analyze the laboratory test result and used Z-score to evaluate the testing ability of each participating laboratory.

A total of 448 laboratories throughout the country participated in the proficiency testing program.341 laboratories(76.1%) of participating laboratories, obtained satisfactory result. Results provided by 28 laboratories(6.3%) of total participating laboratories, were found suspicious in their capacities. Finally, there were 79 laboratories(17.6%) of total participating laboratories, with result found to be outliers.

The statistical result of the interlaboratory comparison project show that the testing capability of lead in drinking water has been ranked as satisfactory in the laboratories of the provincial and municipal centers for disease control and prevention across the country, and the testing capability of a small number of laboratories requires further improvement.