Application of Oscillating Reaction-based Determinations to the Analysis of Real Samples

Abstract

The application of oscillating reactions to the analysis of real samples by the analyte pulse perturbation technique is reported. The oscillating reaction involving the H ₂ O ₂ –NaSCN–CuSO ₄ system in an alkaline medium was used for the expeditious, convenient, automatic determination of vanillin, paracetamol and ascorbic acid in food and pharmaceutical samples. Six methods (two per analyte) were developed that allow the determination of 1.5–40 µmol of vanillin, 0.5–6 µmol of paracetamol and 0.5–5 µmol of ascorbic acid in real samples. The proposed methods are precise (RSD < 5%) and have a reasonable sample throughput (6–10 h ^{- 1} ) for this type of reaction, which can be implemented with modular equipment available at any laboratory. The effect of influential variables and the selectivity of the determinations was studied in relation to the types of sample used. Determinations are virtually direct and require no removal of interfering species. The results were validated by comparison with standard methods.