“Palladiazo” a new selective metallochromic reagent for palladium: Part I the main characteristics of the pure reagent and its reaction with palladium(II) |
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Authors: | JA Pérez-Bustamante F Burriel-Martf |
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Institution: | Department of Analytical Chemistry Spanish Higher Council of Scientific Research, MadridSpain |
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Abstract: | The synthesis and purification of 2,7-bis(4-azophenylarsono)-1,8-dihydroxy-naphthalene 3,6-disulphonic acid is reported. Because of its selectivity for palladium-(II), the name palladiazo is suggested for the reagent. Aqueous solutions of palladiazo are very stable and exhibit 2 absorption maxima located at 540 and 625 nm, the molar absorptivities being 3.3 · 104 and 1.7 · 104, respectively. Palladiazo changes color stepwise and reversibly with increase in hydrochloric acid concentration from 0 to 13 M. A negatively charged complex of type M2L3 is formed with Pd(II) at pH 2.5–3.5, and shows an absorption maximum at 640 nm with a molar absorptivity of (5.7 ± 0.1) ·104; the complex can be readily extracted with diphenylguanidine chloride or quaternary ammonium salts dissolved in n-butanol or higher alcohols. The complex obeys Beer's law at 675 nm in the concentration range 10–250 μg Pd(II)/50 ml. Pb(II), Bi(III), Ce(III) and the rare-earth elements are the only expected cationic interferences. |
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