Determination of seven trace elements in natural waters by neutron activation analysis after preconcentration with 1-(2-pyridylazo)-2-naphthol |
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Authors: | H. Bem D.E. Ryan |
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Affiliation: | Trace Analysis Research Centre, Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4J1 Canada |
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Abstract: | A procedure is described for the preconcentration of Cd(I), Co(II), Cr(III), Cu(II), Mn(II), U(VI) and Zn(II) from 800 ml of water and sea-water samples by coprecipitation with 1-(2-pyridylazo)-2-naphthol (PAN) prior to neutron activation. Chromium is reduced to Cr(III) by hydroxylammonium chloride at pH 4 before the preconcentration step. Coprecipitation of 30 mg of PAN was most effective at pH 9 with final recoveries of 76–91% for six elements and 50% for uranium. The scheme is based on double irradiation of the same samples. Short (10 min) irradiation followed by γ-spectrometry counting for 10 min gives data for Cd (111mCd), Co, Cu, Mn and U (239U). A second 16-h irradiation permits determination of zinc and uranium (239Np) after a waiting time of 6 h, cadmium (115Cd) after 24 h and chromium after a waiting period of 2 weeks followed by counting for 30 min. Detection limits are 0.04 ng g?1 for Co, 0.8 ng g?1 for Cd, 0.3 ng g?1 for Cu, 0.2 ng g?1 for Cr, 0.006 ng g?1 for Mn, 0.006 ng g?1 for U and 0.3 ng g?1 for Zn. A further decrease of the detection limit for chromium to 0.05 ng g?1 can be achieved by separation of interfering nuclides and scintillation counting of 51Cr with a NaI(Tl) well-type detector. |
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