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Title: Inter-laboratory study to improve the quality of the analysis of nutrients in rainwater chemistry
Authors: Karthikeyan, S. 
Balasubramanian, R. 
He, J. 
Keywords: Nitrogen deposition
Precipitation chemistry
Quality assurance
Quality control
Uncertainty analysis
Issue Date: Jul-2009
Citation: Karthikeyan, S., Balasubramanian, R., He, J. (2009-07). Inter-laboratory study to improve the quality of the analysis of nutrients in rainwater chemistry. Atmospheric Environment 43 (21) : 3424-3430. ScholarBank@NUS Repository.
Abstract: This paper describes the results of an inter-laboratory study conducted for the analysis of nutrients (nitrate, ammonium, phosphate, total nitrogen (TN), and total phosphorus (TP)) in natural rainwater. For this purpose, rainwater samples were collected and aggregated in Singapore and homogenized. These samples were immediately filtered through 0.45 μm membrane filters and autoclaved for 15 min at 80 °C in order to stabilize the nutrients. The homogeneity and the stability of nutrients were rigorously tested for a period of three months initially. Upon ensuring the homogeneity and stability, the samples were distributed to 15 different laboratories from various countries around the world (Australia, Brazil, India, Mauritius, Singapore, Slovenia, Spain, Taiwan, and USA). Almost all laboratories have reported the analytical results for nitrate whereas only 8 of the 15 laboratories reported results for other nutrients such as ammonium, phosphate, TN, and TP. The discrepancy was mainly due to the presence of these nutrients in low concentration levels (particularly ammonium ion and phosphate). Not all the laboratories were equipped with analytical capabilities to conduct the analysis of nutrients in low concentration levels. Further, the uncertainty associated with the analysis of TN and TP restricted the number of laboratories that could report their analytical data on nutrients. All 14 laboratories reported nitrate-nitrogen results which were in good agreement with each other (0.68 ± 0.07 mg l-1). Similarly, the results of TN and TP were also comparable among at least 8 laboratories. This inter-laboratory study on the analysis of nutrients in natural rainwater, conducted for the first time, provided an opportunity to the participating laboratories to assess and improve their laboratory performance, thereby, improving the quality of their analytical data. © 2009 Elsevier Ltd. All rights reserved.
Source Title: Atmospheric Environment
ISSN: 13522310
DOI: 10.1016/j.atmosenv.2009.03.025
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