Synthesis of 4-(o-methylbenzeneaminodiazo)-4'-nitroazobenzene and its color reaction with mercury(II)

The synthesis of a new triazene reagent 4-(o-methylbenzeneaminodiazo)-4′-nitroazobenzene(OMADNA) and the optimum conditions of its color reaction with mercury(Ⅱ) were studied.In the presence of emulsifying reagent OP,Hg(Ⅱ) reacts with OMADNA to form a stable orange-red complex in a medium of borax-NaOH buffer of pH 9.5～11.0.The apparent molar absorptivity is 1.42×105 L·mol-1·cm-1.At the maximum absorption of 570 nm,Beer′s law was obeyed in the concentration range of 0～0.9 μg/mL for Hg(Ⅱ).The method has good sensitivity and selecttivity.It has been directly applied to the determination of trace mercury(Ⅱ) in waste water samples and the determination results are in agreement with those by dithizone method.