Two simple extractive spectrophotometric methods were developed for the determination of doripenem in pure and pharmaceutical formulations. Doripenem, a recently developed member of carbapenem class of beta-lactum antibiotic has been shown to have broad-spectrum activity against Gram-positive and Gram-negative pathogens, including strains of Pseudomonas aeruginosa. A Tech-comp model UV-2301 UV-Visible spectrophotometer with 1 cm matched quartz cells was used for all spectral measurements. Aqueous solutions of 0.1% bromo cresol purple (Method-A) and 0.2% methylene violet (Method-B) were used in the present investigation. Freshly prepared working standard solution of doripenem of concentration 200μg/mL and 300μg/mL were used for method A and method B respectively. These methods were based on the formation of colored ion-ion association complex between protonated drug molecule (doripenem having positive charge) and dissociated bromo cresol purple or methylene violet (i.e. reagent molecular ion having negative charge) in the aqueous phase at a suitable pH extractable into dichloromethane or chloroform in Method A and Method B respectively. The absorption spectra were recorded for the colored products and it was evident that the wavelength of maximum absorbance at 417nm and 560nm for methods A and B respectively. The molar absorbitivity and Sandell’s sensitivity of the proposed methods were found to be 6.032x103 &3.843x103 and 0.0697 &0.1094 respectively. Limit of detection and limit of quantitation were observed to be 0.10&0.70 and 0.165&2.31 μg/mL. The developed methods had been statistically validated and applied to pharmaceutical formulations without any interference from excipients.
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