Complex equilibria and spectrophotometric determination of copper with 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol

The complex equilibria of copper with 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol were studied spectrophotometrically using graphical analysis and numerical treatment of the absorbance data by the PRCEK or SPEKTFOT program on a Tesla 200 computer. Of the two reagents, 4-(2-pyridylazo)resorcinol forms more complexes including the 1 : 2 complexes, with a greater bathochromic shift of λmax with respect to the reagent. Especially the CuL2-2 complex of 4-(2-pyridylazo)resorcinol with ε = 7.9 . 104 at 500 nm permits sensitive spectrophotometric determination of copper. Procedures for the spectrophotometric determination of copper in weakly alkaline media were evaluated.