Synthesis of 3,5-bis(3-hydroxy-2-pyridylaminodiazo)-2,4,6-tribromobenzoic acid and its color reaction with copper

A new chromogenic reagent 3,5-bis(3-hydroxy-2-pyridylaminodiazo)-2,4,6-tribromobenzoic acid(BHPADTBBA) was synthesized,and the color reaction of BHPADTBBA with copper was studied.A new spectrophotometric method for the determination of micro copper was thus proposed.The results showed that a red complex of BHPADTBBA and copper was formed in the buffer solution of Na2B4O7-NaOH at pH 10.0 in the presence of TritonX-100.The complex showed a peak of maximum absorption at 570 nm with an apparent molar absorptivity of 2.18×105 L·mol-1·cm-1.Beer's 1aw was obeyed in the range of 0-18 μg/ 25 mL for copper.The method has been applied to the determination of copper in aluminium alloys.The results are consistent with the certified values.