Abstract

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Two simple, selective and sensitive spectrophotometric methods are described for the determination of some aminoglycosides antibiotics: Streptomycin sulphate (STR), neomycin sulphate (NMS) and spectinomycin (SPC). The methods are based on the reaction of the studied drugs with either bromocresol green (BCG), bromocresol purple (BCP), to give yellow species. The coloured products are quantified spectrophotometrically at 430, 477, and 441, for STR, NMS, and SPC, using BCG, respectively, whereas on using BCP at 436, 440, and 466, respectively. The optimization of the different experimental conditions is described. No interferences from different additives and common degradation products were observed in the determination. The BCP method was better than the BCG method, because of its wider range of determination (0.4 - 12 μg mL⁻¹ vs. 0.6 - 18 μg/ mL on using BCP), higher molar absorptivity and Sandell sensitivity (8.26 x 104 L mol⁻¹ cm⁻¹ and 0.007 μg cm⁻² vs. 5.62 × 104 L mol⁻¹ cm⁻¹ and 0.011 μg cm⁻¹), greater stability (24 and 18 days on using BCG and BCP, respectively) and better selectivity.. The stoichiometry of the formed ion-pairs was found to be 1: 1 for all complexes. The proposed methods have been applied successfully for the analysis of the studied drugs in pure forms and pharmaceutical formulations.

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