[Determination of trace amounts of nitrite and reaction mechanism by triple-wavelength spectrophotometry].

A new method was proposed for the determination of nitrite ion by triple-wavelength spectrophotometry. This limits ranges of determination are 0-0.560 mg.L-1 nitrite ion at 599.1 nm, 420.6 nm and 283.4 nm. It has been applied to analysis trace amounts of nitrite ion of standard sample and environmental water with satisfactory result, the relative error was less 1.7% and recovery of the real samples was between 96.5 and 100.0%. This method is based on the diazotization-coupling react of thionine with nitrite ion in acidic medium, the mole ratio of thionine:nitrite is 2:1 by the continuous variation and mole ratio method.