Flow-injection chemiluminescence determination of aminomethylbenzoic acid and aminophylline based on N-bromosuccinimide-luminol reaction

A novel and sensitive chemiluminescence (CL) method for the determination of aminomethylbenzoic acid and aminophylline coupled with flow-injection analysis (FIA) technique is developed in this paper. It is based on the inhibition effect of the studied drugs on the chemiluminescence emission of N-bromosuccinimide-luminol (NBS-luminol) system. Under the optimum conditions, the decreased CL intensity is linear with the concentration of aminomethylbenzoic acid in the range of 2×10⁻⁸ to 1.0×10⁻⁶ g ml⁻¹ and with the concentration of aminophylline in the range of 1×10⁻⁷ to 7.0×10⁻⁶ g ml⁻¹, respectively. The detection limit is 7.0×10⁻⁹ g ml⁻¹ for aminomethylbenzoic acid (3σ) and 3.4×10⁻⁸ g ml⁻¹ for aminophylline (3σ). The relative standard deviations (R.S.D.) for 11 parallel measurements of 2.0×10⁻⁷ g ml⁻¹ aminomethylbenzoic acid and 1.0×10⁻⁶ g ml⁻¹ aminophylline are 2.6 and 3.0%, respectively. The proposed methods have been applied for the determination of the studied drugs in their pharmaceutical formulations with satisfactory results. The possible use of the proposed system for the determination of aminomethylbenzoic acid in plasma sample was also tested. The possible inhibition mechanism of aminomethylbenzoic acid and aminophylline on luminol-NBS system was discussed briefly.