Inverse spectrophotometric detection in flow injection analysis: determination of nitrite using cerium(IV) as the chromophore

Abstract

The application of inverse spectrophotometric detection in flow injection is introduced and its potential illustrated by a possible application to the determination of nitrite by its reaction with cerium(IV).

A single manifold was employed with two reagent concentrations, namely 10 and 20 g l^–1, of cerium(IV) ammonium sulphate in 0.5 M sulphuric acid. The working ranges are 10–200 and 200–1000 mg l^–1, respectively, for a ca. 30-µl sample injection and the sampling rate is between 60 and 75 injections per hour. The 200–1000 mg l^–1 system was applied to the determination of nitrite in culture media and the results were compared with those given by a manual diazotisation method.

The same manifold with a smaller sample loop was also employed to demonstrate the extension of the technique to provide chemical back-off. A working range of approximately 2500 mg l^–1 of nitrite can be covered anywhere between 1000 and 9000 mg l^–1 simply by selection of a suitable reagent concentration.