Simple fluorimetric method for determination of certain antiviral drugs via their oxidation with cerium (IV)

A simple and sensitive fluorimetric method for determination of antiviral drugs: ribavirin, acyclovir, and amantadine hydrochloride has been developed. The method was based on the oxidation of these drugs by cerium(IV) in presence of perchloric acid and subsequent monitoring the fluorescence of the induced cerium(III) at λ_excitation 255 and λ_emission 355 nm. Different variables affecting the reaction conditions such as the concentrations of cerium(IV), type and concentration of acid medium, reaction time, temperature, and the diluting solvents were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9978–0.9996) were found between the relative fluorescence intensity and the concentrations of the investigated drugs in the range of 50–1400 ng ml^–1. The assay limits of detection and quantitation were 20–49, and 62–160 ng ml^–1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 1.58%. No interference could be observed from the excipients commonly present in dosage forms. The proposed method was successfully applied to the analysis of the investigated drugs in pure and pharmaceutical dosage forms with good accuracy and precision; the recovery percentages ranged from 99.2 to 101.2 ± 0.48–1.30%. The results obtained by the proposed fluorimetric method were comparable with those obtained by the official method stated in the United States Pharmacopoeia.