Synthesis of 2-[2-(4-methylquinolyl)azo]-5-diethylaminophenol and its use for the spectrophotometric determination of nickel

2-[2-(4-Methylquinolyl)azo]-5-diethylaminophenol (QADP) was synthesized and the acidity constants of the reagent in 50% (v/v) ethanol and reactions with various metal ions were studied. QADP and its chelates are extracted into chloroform and the molar absorptivities of most complexes are higher than 10 5 1 mol −1 cm −1. QADP was applied to the selective spectrophotometric determination of nickel. Nickel (0.4–7.2 μg) could be determined by masking cobalt as the Co(III)-ammine complex.