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

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.