Evaluation of bias, precision, and systematic errors in proficiency testing of Cl− and Cu concentration in water

The proficiency testing exercise was conducted to assess the quality of water testing in several laboratories in India. The 11 participants from all over India gathered at one place and attended the workshop organized at NEERI, Nagpur. The test samples were analyzed for Cl − (Chloride) and Cu (Copper) concentration in water. The objective of the study was to determine bias and precision among participants for the analysis of Cl − and Cu concentration. Statistical analysis indicated that most of the measurement results were overestimating the Cl − concentration and underestimating the Cu concentration. The presence of systematic error identified the need for further improvement in determining the Cu concentration in water by the participants.