Difference Spectrophotometric Method Development for the Estimation of Acyclovir

A simple, precise and accurate difference spectroscopic method has been developed for the estimation of Acyclovir in bulk and in pharmaceutical dosage form. The proposed method is based on the principle that Acyclovir can exhibit two different chemical forms in basic and acidic medium that differ in the absorption spectra in basic and acidic medium. Since the drug was freely soluble in distilled water, a stock solution (1 mg/mL) was prepared with distilled water. Further dilution was made by using 0.1 M sodium hydroxide and 0.1 M hydrochloric acid separately. The maxima and minima in the difference spectra of Acyclovir were at 256 nm. Difference in absorbance between these maxima and minima was calculated to find out the amplitude. This amplitude was plotted against concentration. Beer's law is valid in the concentration range of 1-5 μg/mL. As per ICH guidelines results of analysis were validated statistically and all the results were found satisfactory.