Fluorimetric determination of isoniazid by oxidation with cerium(IV) in a multicommutated flow system

A multicommutated flow system for the indirect fluorimetric determination o f isoniazid was proposed. The analytical procedure was based on the oxidati on of isoniazid by cerium(IV) and monitoring of the fluorescence intensity of the formed cerium(III). A time-based sample insertion enabled an effecti ve control of the sampled volume and thus of the dispersion level attained. Highly concentrated samples were subject to a zone sampling approach, cons isting on the removal to waste of selected sample portions, which acted as a selective dilution procedure enabling the expansion of the linear working range of concentrations without need for manifold re-configuration. These features were evaluated in automated dissolution studies. Linear calibration plots up to 1.37 mu-g ml(-1), with a relative standard d eviation of less than 1.6% (n=12) and a sample throughput of about 50 sampl es per hour, were obtained. The lower detection limit was 34.3 ng ml(-1). T he methodology was evaluated in the determination of isoniazid in pharmaceu tical preparations and the effect of potential interferences was investigat ed. (C) 2000 Elsevier Science B.V. All rights reserved.