[Spectrophotometric studies on and applications of the reaction of copper with 2-hydroxy-3-carboxy-5-sulfobenzenediazoaminoazobenzene].

A highly sensitive color reaction of copper(II) with 2-hydroxy-3-carboxy-5-sulfobenzenediazoaminoazobenzene (HCSDAA) in the presence of Triton N-101 was studied in detail. In borax buffer medium at pH 10.4-11.5, the red complex formed has a maximum absorption at 530 nm and its apparent molar absorptivity is 1.31 x 10(5)L x mol(-1) x cm(-1) and sandell sensitivity is 4.85 x 10(-4) microg x cm(-2). The molar ratio of copper(II) to HCSDAA in the complex is found to be 1:2. Beer's law is obeyed in the concentraction range of 0-0.24 microg/mL for copper. The proposed method has been applied to the spectrophotometric determination of microamounts of copper in ore and peanut with the relative error and the relative standard deviation (n = 6) of less than 3.7% and 1.6%, respectively.