Abstract
Polymyxins (PMS), namely Colistin (CS) and polymyxin B (poly B), are antimicrobial drugs that have been recently used to treat multiresistant Gram‐negative bacteria infections and their resurgence, owing to a lack of new antibiotics. A speedy, simple, and ultrasensitive spectrofluorimetric screening of PMS in pharmaceutical formulations and biological fluids was urgently required from this point forwards. A reaction between fluorescamine and the aliphatic amino moiety found in both drugs was performed in a slightly alkaline borate buffer (pH 8.5) resulted in highly fluorescent products measured at λem 460 (after λex 390.5 nm). Linear calibration curves were constructed over the concentration range 70–1800 ng ml−1 and 100 to 1400 ng ml−1, with slope values of 0.273 and 0.286, correlation coefficients of 0.9998 and 0.9997, and determination coefficient of 0.9997 and 0.9994 for poly B and CS, respectively. The ultrasensitivity of the proposed method was demonstrated by the very low limit of quantification values of 67.56 ng ml−1 and 94.89 ng ml−1 for poly B and CS, respectively. The cited drugs were successfully determined in their intravenous market preparations by the prescribed method. Moreover, due to the high sensitivity, the suggested method was used to assay the investigated drugs in biological fluids.
The studied medications reacted with fluorescamine in borate buffer to produce a highly fluorescent stable derivative measured at λem 460 nm (λex 390.5 nm). Factors affecting fluorescence intensity of the resultant diarylpyrrolone derivative were cautiously examined and adjusted. Validation of analytical methods according to International Conference on Harmonization guidelines was done. The described method was used effectively on the commercially parenteral dosage forms. The method was capable of the estimation of the investigated parenteral in human plasma.