A simple, rapid, sensitive, and reproducible procedure for assaying norfloxacin (NOR), ciprofloxacin (CIP), and ofloxacin (OFL) was investigated. The procedure is based on the reaction of selected drugs with Sudan II (I), Congo red (II), and Gentian violet (III) in universal buffer to give soluble ion‐pair complexes. The effects of various parameters have been studied. Beer's law plots were obeyed in the concentration ranges 0.5–11 µg ml, whereas Ringbom optimum ranges were 0.7–9.5 µg ml. The apparent molar absorptivity (6.4×10 L mol cm), Sandell sensitivity (4.99 ng cm), detection (0.13 µg ml), and quantification (0.44 µg ml) limits were calculated. The relative standard deviation for ten determinations, for samples containing 4.0 µg ml, was found to be 1.40%. The influence of commonly employed excipients in the determination of the studied drugs was examined. There was no interference from degradate product results from thermal and hydrolytic treatments. The results obtained by the proposed procedure were statistically validated. The developed procedure was successfully applied to the determination of the studied drugs in dosage forms and biological fluids.
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