Micelle-mediated spectrofluorimetric determination of ampicillin based on metal ion-catalysed hydrolysis

A spectrofluorimetric study based on the metal-ion catalytic degradation of the alpha-amino beta-lactamic antibiotic ampicillin, in micellar media has been carried out. Different surfactant systems and metal ions were tested in order to enhance the analytical performance characteristics of the system. Results demonstrated that copper(II) ions were the most effective acting as catalyst and that the fluorescence intensity of the reaction products (measurement at 343 and 420 nm as excitation and emission wavelengths, respectively) was effectively enhanced in presence of anionic surfactants. Through variation of experimental conditions (temperature, pH, nature of buffer, reaction time) a selective and sensitive spectrofluorimetric batch method was developed for ampicillin determination. Also, a multisimplex design was used to determine the optimal values in a flow injection analysis (FIA) format and pH, flow rate and temperature were the variables considered. In the optimal experimental conditions, linear relationships were obtained, between intensity of fluorescence and concentration of ampicillin in the range of 2-10 muM for batch and flow systems and the detection limits were found to be 4.0 x 10(-7) M and 5.2 x 10(-7) M, respectively. The FIA method is rapid, simple, reproducible, selective and accurate within +/-4.6% (6 muM ampicillin level). The method was applied to ampicillin determination in different dosage forms without interference effects. (C) 2003 Elsevier Science B.V. All rights reserved.