Sensitive Flow-Injection Chemiluminescence Determination of Metformin Based onN-Bromosuccinimide-fluorescein System

A novel and sensitive flow-injection chemiluminescence (CL) method for the determination of metformin in pharmaceutical formulations over the range of 7 × 10−9–3 × 10−5 g mL−1 is proposed in this article. The method is based on the CL produced during the oxidation of N-bromosuccinimide (NBS) in alkaline medium in the presence of fluorescein as an effective energy transfer agent. Use of cetyltrimethylammonium bromide (CTAB) as a sensitizer enhances the signal magnitude about 100 times. The detection limit is 2.3 × 10−9 g mL−1 (3σ) with a relative standard deviation of 2.7% (n = 11) at 1 × 10−7 g mL−1 metformin. Ninety samples can be determined per hour. The method was evaluated by carrying out a recovery study and by the analysis of commercial formulations. The results obtained compared well with those obtained by pharmacopoeia method and demonstrated good accuracy and precision. The possible reaction mechanism of the CL in the system is also discussed briefly.