A Green Electroanalytical Method for the Determination of Levofloxacin by Ion-Pair Formation with Picric Acid

Levofloxacin (LFX), an antimicrobial agent has been detected by using picric acid (PA) as an anionic reagent in aqueous medium. On mixing the reactants in distilled water yellow colored product is separated within two minutes which was found to be an ionassociation complex (LFX-PA) of both the reactants. Spectroscopic and voltammetric studies were carried out to explain the interaction between levofloxacin and picric acid. Spectroscopic study of the ion-pair product confirmed its formation as determined from substantial shift in respective λmax values. In voltammetric experiments, a shift of 70 mV was noticed in an anodic peak of LFX-PA (1.64V) accompanied with a large decrease in peak current. In addition, a number of new peaks appeared in voltammogram of LFX-PA. Similarly, in case of cathodic cycle, new peaks appeared in differential pulse voltammogram of the ion-pair which proved the interaction of the PA and LFX. A calibration curve was drawn using the peak current values of the LFX. The linear increase in peak current with increasing LFX concentration was obtained in the concentration range 1.5×10-3 M – 6.0×10-3 M with R2 = 0.994. A study on the solvent effect on the spectrometric as well as voltammetric methods for LFX suggested that water is the best medium for the study. Stability of the complex was also determined by computational methods using DFT/B3LYP/6-31G basis sets. Further, analysis of LFX in commercially available drug tablets proved that the proposed method is valid in real life sample analysis.