Determination of trace metals in lake waters by X-ray fluorescence after a precipitation preconcentration

A preconcentration technique based on selective precipitation was employed in combination with wave-length dispersive X-ray fluorescence spectrometry (WDXRF) to extend the range of application of XRF and make possible the analysis of trace metals in naturals water samples. The precipitant used was a bidentate chelating agent, disodium, piperazino-1, 4-bis(dithio-carbamate) synthesized in the laboratory. Water samples from six lakes in the Sudbury area were analyzed by this combined technique. To test the accuracy, a Certified Reference Materials, SLRS-3, was analyzed by WDXRF after the preconcentration step. The same samples were also analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS) to verify the quality of the preconcentration method. The reliability of ICP-MS and GFAAS was confirmed by the fact that the concentrations of trace metals in SLRS-3 generally matched the certified values. A general comparison of the instrumental techniques and an environmental implication based on the results are given in this paper.