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Report of the Inter-laboratory Comparison on Nitrite and Lead in Water 2019

The first round of the Inter-laboratory Comparison on Nitrite and Lead in Water 2019 was conducted by Water Quality Analysis Laboratory of Research Center for Eco-Environmental Sciences (RCEES), Chinese Academy of Sciences (CAS), together with CAS-TWAS Centre of Excellence for Water and Environment (CEWE). This activity is supported by Certification and Accreditation Administration of People’s Republic of China (CNCA).

This study included the determination of nitrite-N and lead in two different water items, which were both distributed to the participating laboratories in two concentration levels. The objectives of this inter-laboratory comparison study were

A. To offer a tool for quality assurance to the participating laboratories

B. To assess the between laboratory reproducibility

C. To assess the willingness of expert laboratories along the Belt and Road to determine levels of elements in regular water.

D. To provide a general overview of the analytical performance of laboratories along the Belt and Road.

Thirty two test samples were sent to 19 different laboratories from 15 countries along the Belt and Road, and results were returned from 29 of these. This report presents the reported results for all 15 test samples of lead (each was prepared in two concentration levels) and 14 test samples of nitrite (each was prepared in two concentration levels).

The assigned concentration for each analyte in the test samples was determined by National Institute of Metrology, China. All values exceeding ±50% of the assigned concentrations were removed from the calculation. The consensus mean and the standard deviation (SD) were calculated from the remaining data, while this SD and the assigned concentration were used to subsequently calculate Z-scores because only 14/15 reported results for each analyte were collected and the outliers would contribute to a large degree.

For the sample of Lead a, Z-scores within ±1 were obtained by 46.7% of the reporting participants, and Z-scores within ±2 were achieved by 60% of the participants (corresponding to 9 of the total 15 participants). For the sample of Lead b, Z-scores within ±1 were obtained by 46.7% of the reporting participants, and Z-scores within ±2 were achieved by 66.7% of the participants (corresponding to 10 of the total 15 participants).

For the sample of Nitrite-N-a, Z-scores within ±1 and ±2 were obtained by 64.3% of the reporting participants (corresponding to 9 of the total 14 participants). For the sample of Nitrite-N- b, Z-scores within ±1 were obtained by 57.1% of the reporting participants, and Z-scores within ±2 were achieved by 71.4% of the participants (corresponding to 10 of the total 14 participants).

Click the following link to download the full Report.

Report of the Inter-laboratory Comparison on Nitrite and Lead in Water 2019.pdf