Water arsenic, fluoride and chloride detection capability assessment of the drinking water monitoring Labs in Guangdong province

Objective To assess the proficiency of water monitoring laboratory at rural, county, and provincial levels in Guangdong province, to ensure the province's drinking water monitoring results accurate and reliable. Methods State quality of certified reference materials as water arsenic, fluoride and chloride of 90 copies each were numbered and distributed to 90 monitoring laboratories in the province for testing, The measurement results of the participatory labs were evaluated through normative values and expanded uncertainty, and were compared with those of robust statistics method. Results All participatory labs had timely feedback of their measurement results. The qualified rate was higher when arsenic was tested by hydride generation atomic fluorescence spectrometry and zinc-new silver salt of sulfuric acid spectrophotometric system, while fluoride and chloride by ion chromatography. The average qualified rates of water arsenic, fluoride and chloride of the province's rural drinking water quality monitoring laboratory were 66% (59/90), 72% (65/90) and 72% (65/90), respectively.Seven participatory labs failed the proficiency testing of all three analytes and unqualified rate was 7.8% (7/90)among the ninety participated monitoring labs. The qualified rates of robust statistics method for arsenic fluoride and chloride were greater than those evaluated by the expanded uncertainty, and large deviations with small sample sizes. Conclusions The testing ability of drink-water monitoring labs in Guangdong province has improved.However, by comparison with the requirements of national quality control and testing skills, there is still a gap. It is suggested that internal quality control be included in routine inspeetion to improve laboratory testing technology. Key words: Drinking; Quality control ; Arsenates; Fluorides; Chlorides