Simple Flow Injection Analysis System for the Spectrophotometric Determination of Trace Amounts of Nitrite in Water Samples

A simple and sensitive spectrophotometric flow injection analysis system has been developed for the determination of trace amounts of nitrite. The method is based on the reaction of nitrite with sulfanilamide in acidic medium to form a diazonium salt which then couples with thenoyltrifluoroacetone in alkaline medium to give an azo dye. Beer’s law is obeyed at 470 nm over a nitrite concentration range of 1-1200 μg L, and a detection limit for nitrite is 0.3 μg L is achieved with a relative standard deviation of 1.4% at 50 μg L (n=8). An injection rate of about 40 h is possible using this method, which was successfully applied to the determination of nitrite in rain water, tap water, pond water, and river water samples.