SIMULTANEOUS DETERMINATION OF ISONIAZID AND
RIFAMPICIN BY UV SPECTROPHOTOMETRY
MARIANA TILINCA1, GABRIEL HANCU2*, ELEONORA MIRCIA3, DIANA IRIMINESCU2, AURA RUSU2, ROBERT ALEXANDRU VLAD2, ENIKŐ BARABÁS4
1Cell and Molecular Biology, Faculty of Medicine, University of Medicine and Pharmacy Târgu Mureș, Romania
2Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Medicine and Pharmacy Târgu Mureș,
Romania
3Department of Organic Chemistry, Faculty of Pharmacy, University of Medicine and Pharmacy Târgu Mureș, Romania
4Department of Botany and Cell Biology, Faculty of Pharmacy, University of Medicine and Pharmacy Târgu Mureş,
Romania
*corresponding author: gabriel.hancu@umftgm.ro
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Abstract:
One of the most effective antituberculosis treatments is the combination between isoniazid and rifampicin. Two alternative
UV spectrophotometric methods were developed for the simultaneous determination of isoniazid and rifampicin in mixture,
by employing simultaneous equation method and first-derivative spectrophotometry respectively. The determinations were
performed in methanol. In the simultaneous equation method, the absorbtion maxima of the two drugs, 263 nm and 338 nm,
were selected for estimation of isoniazid and rifampicin respectively. The second method was based on a first-derivative
spectrophotometric method involving the determination of the analytes at their respective zero crossing point, the
determinations were made at 263 nm for rifampicin and 290 nm for isoniazid respectively. Both substances obeyed Lambert-
Beer’s law in a concentration range between 5 - 50 μg/mL. The analytical performances of the proposed methods were
verified regarding their accuracy, linearity, precision, selectivity and sensitivity according to ICH guidelines. The proposed
methods can be successfully applied in routine laboratory analysis for the determination of isoniazid and rifampicin in
combined dosage forms.

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