Synthesis of N-sulfoalkyl derivatives of 2-(2-pyridylazo)-5-aminophenol and the spectrophotometric determination of uranium(VI)

Six N-sulfoalkyl derivatives of 2-(2-pyridylazo)-5-aminophenol were synthesized. The acidity constants of the reagents and the stability constants of several of their metal complexes were determined. Their application to the spectrophotometric determination of metals in aqueous solution was studied. 2-(3,5-Dibromo-2-pyridylazo)-5-[N-ethyl-N-(3-sulfopropyl)amino]phenol was found to be a highly sensitive reagent for some metal ions. The molar absorptivities (1 mol-1 cm-1) of metal complexes at lambdasub(max) (nm) are 66000 (592 nm) for uranium(VI), 138000 (560 nm) for zinc, 70000 (558 nm) for copper(II) and 88000 (568 nm) for iron(II). The effects of various maskings agents were examined. The determination of uranium(VI) is described in detail. (Auth.)