A general difference spectrophotometric procedure for the determination of seven antibacterial 7-piperazine fluoroquinolone derivatives in the range of 2-20 µg/ml is proposed. The procedure is based on the oxidation of these antibiotics using 1 ml of 0.5 mg/ml potassium permanganate in presence of 20% sulphuric acid at room temperature (25±5°C) for 10 min. The decrease in permanganate color (DA) due to the interaction with such organic compounds is measured at 520 nm. Molar ratio determination indicated 1:3 (drug: permanganate). Assay precision (RSD) values were ±1.5% or better for the bulk drugs and ranged from ±1.38 to ± 1.2% for tablets and ampoules. Drug recoveries were quantitative from the dosage forms tested. The proposed procedure is simple, rapid, accurate and readily applied to the determination of this new class of antibiotics in pharmaceutical products without interference from other ingredients or common additives.
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