Flow-injection chemiluminescence determination of isoniazid using on-line electrogenerated BrO^– as an oxidant

By designing a novel electrolytic flow cell, the strong oxidant BrO^– was electrogenerated on-line in KBr solution and its concentration could be readily adjusted on-line with the flow-injection technique and an electrochemical method. The chemical reaction between BrO^– and luminol in alkaline medium is accompanied by weak emission of light due to chemiluminescence (CL). It was found that the isoniazid can greatly enhance this weak CL intensity when present in the luminol solution. Based on this observation, a new flow-injection CL method for the determination of isoniazid had been proposed in this paper. The detection limit was 7.0 × 10^–9 g ml^–1 isoniazid and the CL emission intensity was correlated with the isoniazid concentration in the range 2.0 × 10^–8–1.0 × 10^–6 g ml^–1 with an RSD of <5% (n = 7). The system was applied successfully to the determination of isoniazid in pharmaceutical preparations and the possible CL mechanism is discussed.