Flow injection spectrophotometric determination of cyclamate in low calorie soft drinks and sweeteners

A flow injection spectrophotometric procedure is proposed for the determination of cyclamate in low calorie soft drinks and sweeteners. The system is based on the reaction between nitrite and cyclamate in a medium containing 0.1 mol l–1 phosphoric acid; the excess of reducing agent is determined by the Griess reaction. The flow system is designed to provide a residence time compatible with the rate of the redox process. To eliminate interference caused by dye additives an alumina column is used. During the sampling stage, the dyes are removed and the loop, positioned in series, becomes filled with the colourless sample solution. After sample injection, the alumina column is regenerated by an alkaline solution flowing in the opposite direction. Cyclamate was determined in nine diet products. Some results were compared with those obtained by a bi-amperometric procedure (correlation coefficient, r= 0.9999, n= 4) and others were compared with label values (r= 0.9965, n= 5). The detection limit was 3.0 × 10–5 mol l–1 and the relative standard deviation was less than 0.5% for a solution containing 8.0 × 10–4 mol l–1 of cyclamate (n= 12). The proposed system allowed us to obtain 24 results h–1 and this was limited by the on-line adsorption of dyes on the alumina column.