Synthesis of 4-(p-methoxyphenyaminodiazo)-4'-nitroazobenzene and its colour reaction with mercury

A new reagent 4-(p-methoxyphenyaminodiazo)-4'-nitroazobenzene(PMADNA)was synthesized and its colour reaction with mercury was studied.In the presence of Tirton X-100,Hg reacts with PMADNA to form a red complex with molar ratio of 1∶2 in the medium of borax-NaOH buffer of pH 10.5.The maximum absorption wavelength is located at 576 nm and the molar absorptivity of the color reaction is 1.25×105 L·mol-1·cm-1.Beer's law is obeyed in the range of 0-0.8 μg/mL for mercury.The allowance amounts of Fe3+,Ni2+,Cu2+,Cd2+ are enlarged using sodium tartrate-sodium pyrophosphate-sodium fluoride as masking rergent.The method has been directly applied to the determination of mercury in waste water with RSD of 1.8 %-2.2 % and recovery of 99.1%-103.8%.