Objective To further improve the water testing capability through a proficiency test of ammonia and volatile phenol in water.
Methods The level of ammonia was tested by a Nessler spectrophotometry and the level of phenol was tested by a 4-AAP-chloroform extraction spectrophotometry. Z-score was used to evaluateand predicate test results.
Results In the ammonia test, the Z-score of tests among laboratories (ZB)was 0.35 and the Z-score of tests within the same laboratory (ZW)was 0.22; in the phenol test, ZB was -1.12 and ZW was 0.54. It indicated that both tests met the proficiency requirement (both|Z|≤ 2).
Conclusion The proficiency tests suggestion couple of key issues in laboratory management, such as internal quality control procedure, reagents' preparation and operation, purified water and blank controls.
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