Spectrophotometric determination of hydrazine

A simple sensitive and selective method is described for the determination of trace amounts of hydrazine. The method is based on the reduction of nitrate to nitrite. Hydrazine in ammoniacal condition is used as reducing agent with copper(II) as catalyst. The nitrite prepared is determined based on the diazo coupling reaction between p-nitroaniline and N-(1-naphthyl)ethylenediammine dihydrochloride(NEDA). The method obeys Beer's law in the concentration range of 0-15 mu g of hydrazine in a sample volume of 10 ml at 545 nm and the colour is stable for 3 h. The molar absorptivity is calculated to be 3.83 x 10(4) l/mol/cm with a correlation coefficient of 0.999. The relative standard deviation is 1.8% (n = 10) at 12 mu g of hydrazine. Interferences due to foreign ions have been studied and the method has been applied for the determination of hydrazine in boiler feed water.