Synthesis of 1-(4-nitrophenyl)-3-(3,5-dibromopyridyl)-triazene and its color reaction with copper

The synthesis of a new reagent 1-(4-nitrophenyl)-3-(3,5-dibromopyridyl)-triazene (NPDBPDT) and its color reaction with copper are studied. In the medium of pH 11.0 Na2B4O7—NaOH buffer solution and in the presence of surfactant OP,copper with the chromogenic reagent reacts to form a complex with a molar ratio of 1∶4. The complex has a positive peak at 460 nm and a negative peak at 540 nm.The apparent molar absorptivity of 2.02×105 L·mol-1·cm-1was found by using double-wavelength spectrophotometry,using the reference wavelength of 540 nm and the determination wavelength of 460 nm. Beer's law is obeyed in the range of 0.2—12 μg for copper in 25 mL solution. The detection limit is 7.43×10-9 g/mL. This method has been applied to the determination of copper in copper ore and aluminum alloy samples with RSD of 1.63% and 1.56%,respectively. The results of the method are in agreement with those of AAS.