Precise and sensitive determination of nitrite by coulometric backtitration under flow conditions

A novel method performing for coulometric backtitrations in flow channels w as developed, which was applied for the precise and sensitive determination of low concentrations of nitrite. Under acid conditions nitrite is reactin g stoichiometrically with hydrazine, the remained excess of which is backti trated with electrogenerated bromine. The titration course is recorded eith er amperometrically or chemiluminometrically. Hydrazine can be determined p recisely and accurately in the range between 0.1 mu M and 1 mM without cali bration. Nitrite is reduced by hydrazine according to the reaction 2 NO2- 2 H+ + NH2-NH2--> N2O + N-2 + 3 H2O. Applying the amperometric and the che miluminometric end-point location nitrite was determined accurately and pre cisely in the ranges 0.25-65 mu M and 0.10-50 mu M, respectively. The metho d was applied to the determination of nitrite in tap and river water.