INTERLABORATORY PROGRAM FOR THE QUALITY-CONTROL OF NITRATE DETERMINATION IN FRESH-WATER

Analyses of freshwaters and groundwaters are routinely performed to mo nitor the level of contamination by, e.g., nitrates. To verify the qua lity of such determinations, the Community Bureau of Reference (BCR) h as organised an interlaboratory exercise which allowed to identify mos t of the pitfalls observed in the determination of nitrate at three le vels of concentrations (0.5, 8 and 53 mg kg 1). In addition, this firs t step enabled the BCR to study the feasibility of the preparation of candidate certified reference materials (CRMs) for the determination o f nitrate in freshwater. The materials used in this exercise were care fully prepared and their homogeneity and stability were verified by us ing a flow-injection analysis technique developed for this purpose. Th is paper presents the main results of the intercomparison.