Absorptiometric determination of palladium with 2,3-quinoxalinedithiol |
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Authors: | Dalzol J A Slawinski A K |
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Institution: | Department of Chemistry Chelsea College of Science and Technology Manresa Road, London, S.W.3, U.K. |
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Abstract: | A method is described for the absorptiometric determination of palladium, in the range 0.1-2.5 ppm, with 2,3-quinoxalinedithiol (H(2)qdt) in aqueous ethanol. The reagent, S-2-(3-mercaptoquinoxalinyl) thiuronium chloride (mgt), is hydrotysed rapidly to (qdt)(2-) at pH 10. In the presence of zinc, (qdt)(2-) is stabilized by complex formation and reagent blanks are reduced almost to zero. An anionic 1:2 complex of palladium(II) and (qdt)(-2) is formed at pH 10, having maximum absorbance at 454 nm and Sandell sensitivity index of 0.0032 mug cm (2). The reaction is moderately selective; equivalent concentrations of platinum(IV), iridiuin(IV) and rhodium(III) can be tolerated but gold(III), copper(II) and a few other metals interfere. Suggestions are made for masking interferences. The method is characterized by good precision, with a relative standard deviation of 0.25% at the 1-ppm level. |
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