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(70-27) Interlaboratory Comparability of Copper Complexation Capacity Determination in Natural Waters. Gardner, Michael*,1, Comber, Sean1, vanveen, Eleanor1, 1 WRc-NSF, Marlow, Bucks ABSTRACT- The results of a test of interlaboratory comparability for the determination of copper complexation capacity and copper-ligand complex formation constant will be presented. Participants in the test were chosen on the basis that they had recently published in the scientific literature measured data on copper complexation. Eight water samples comprising, six natural waters, a synthetic ligand solution and a blank solution were analysed by seven laboratories using their own methods of complexation titration. Given the wide variation that might have been possible, relatively good comparability was demonstrated amongst the variety of methods for determining copper complexation capacity. The complexation capacity data largely satisfied the predefined criterion of agreement to within a factor of two. This provides support for the use of metal speciation criteria in the regulation of copper in the environment. Data for the determination of complex formation constants were of poorer comparability, ranging between log K' values of 7 and 12 for the same water. Good comparability was observed for the determination of dissolved copper. Key words: copper complexation, interlaboratory, comparability |
