Flow-injection spectrophotometric determination of hydrazine

A flow-injection spectrophotometric method for the determination of hydrazine is described. The method is based on the inhibitory effect of hydrazine on the reaction of thionine with nitrite in acidic media. The decolorization of thionine by the reaction with nitrite was used to monitor the reaction spectrophotometrically at 602 nm. The variables that affected the reaction rate were fully investigated and the optimum conditions were established. Hydrazine can be determined in the range 2.0-40.0 mu g/ml with a limit of detection of 1.0 mu g/ml. The relative standard deviation for 10 replicate determinations of 7.0 mu g/ml hydrazine is 3.3%. The method is simple, rapid, and widely applicable. (C) 1997 Academic Press.