Kinetic determination of nitrite in waters by using a stopped-flow analyser
Abstract
Automatic kinetic methods for the determination of nitrite in waters with a stopped-flow analyser are described. The methods are based on the diazotisation of sulphanilamide, the product being coupled with N-(1-naphthyl)-ethylenediamine dihydrochloride to form a highly coloured azo dye, which is measured at 540 nm. A single-point kinetic procedure uses a delay time of 10 s and one measurement of 0.7 s. A multi-point reaction rate method uses a delay time of 0.8 s and a measurement time of 1.5 s. The methods are fast, sensitive, accurate and precise, and without serious interference. The sample throughput for routine analysis can be up to 360 samples per hour in the range 0.025–2.00 p.p.m. of nitrite-nitrogen.