The ratio spectra derivative spectrophotometric method was developed for resolving binary mixture of cefixime trihydrate and levofloxacin hemihydrate in tablet formulation. The method involves the use of the first derivative of the ratio of spectra. The absorption spectrum of mixture was obtained and the amplitudes at appropriate wavelengths were divided by the corresponding amplitudes in the absorption spectrum of standard solution of one of the components, and the first derivative of the ratio spectrum was obtained. For the determination of cefixime trihydrate, 4 µg/mL solution of levofloxacin hemihydrate was used as divisor and the 1DD (∆λ=8) amplitudes at 318.6 nm, were plotted against levofloxacin hemihydrate concentration; while – by using 4 µg/mL solution of levofloxacin hemihydrate as divisor – the 1DD (∆λ=8) amplitudes at 338.4.6 nm were found to be proportional to cefixime trihydrate concentration. The calibration curve was established in concentration range of 2-24 µg/mL with correlation coefficient of 0.9960, and 2-14 µg/mL with correlation coefficient of 0.9998 for cefixime trihydrate and levofloxacin hemihydrate, respectively, by measuring signal in respective first derivative ratio spectra. Results of analysis were validated statistically and recovery study. The method has been applied for resolving binary mixture of cefixime trihydrate and levofloxacin hemihydrate in tablet formulation.
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