Study on color reaction of 2-(5-carboxy-1,3,4-triazolylazo) 5-diethylaminobenzoic acid with zinc

The color reaction of the reagent 2-(5-carboxy-1,3,4-triazolylazo)-5-diethylaminobenzoic acid(CTZDBA) with Zn~2+ is reported.It is found that this color reagent reacts with Zn~2+ to form a stable purple red complex(1∶2 by mole) in the medium of NH_3·H_2O-NH_4Cl at pH 8.0.The maximum absorption wavelength of the complex is 545 nm,and apparent molar absorptivity is e=4.13×10~4 L·mol~-1·cm~-1.Beer′s law is obeyed in the range of 0.08-0.8 mg/L for zinc,and the detection limit is 1.57 ×10~-8 g/ mL.The method has been applied to the direct determination of trace zinc in magnesium alloy and aluminium alloy samples.The results are in agreement with the certified values.