Titrimetric and Spectrophotometric Assay of Ganciclovir in Pharmaceuticals Using Cerium(IV) Sulphate as the Oxidimetric Agent

Titrimetric and spectrophotometric assay of ganciclovir (GNC) is described using cerium(IV) sulphate as the oxidimetric reagent. The methods are based on the oxidation of GNC with a measured excess of cerium(IV) sulphate in acid medium followed by determination of the unreacted oxidant by two different reaction schemes. In titrimetry, the unreacted oxidant was determined by back titration with ferrous ammonium sulphate (FAS) in sulphuric acid medium, and spectrophotometry involves the reaction of residual cerium(IV) with p-DMAB to form brownish-coloured p-dimethylamino quinoneimine whose absorbance was measured at 460？nm. In both methods, the amount of cerium(IV) sulphate reacted corresponds to GNC concentration. Titrimetry is applicable over 3–10？mg range where as, in spcetrophotometry, the calibration graph is linear over the range of 2–10？μg？mL？1 and the calculated molar absorptivity value is 1 . 9 6 0 × 1 0 4 ？L mol？1？cm？1. The validity of the proposed methods was tested by analyzing pure and dosage forms containing GNC. Statistical treatment of the results reflects that the proposed procedures are precise, accurate, and easily applicable for the determination of GNC pure form and in pharmaceutical formulations. 1. Introduction Ganciclovir (GNC) chemically known as 2-amino-9-{[(1,3-dihydroxypropan-2-l)oxy]methyl}-6,9-dihydro-3H-purin-6-one (Figure 1) is a nucleoside analogue widely used in the treatment of cytomegalovirus infections. Figure 1: Structure of Ganciclovir. It has been proved effective against cytomegalovirus in immunocompromised patients, mainly in those with the acquired immunodeficiency syndrome (AIDS), congenital immunodeficiency, or in individuals following organ transplantation [1, 2]. Various techniques have been developed for the determination of GNC in pharmaceuticals. It is official in the United States Pharmacopoeia [3]. The most extensively used technique for the quantitation of ganciclovir is HPLC, but most of the procedures using this technique are devoted to body fluids like plasma [8–18], tissues [19], serum [20], and blood samples [21]. HPLC has also been applied for the determination of GNC in eye drops [22]. GNC in bulk drug and in its formulations has been assayed by UV-spectrometry by measuring the absorbance of drug in 0.1？M HCl and 0.1？M NaOH at 253 and 266？nm, respectively. The methods are reported to be moderately sensitive with molar absorptivity values of ~ 2 . 0 × 1 0 3 . There are only three reports on the use of visible spectrophotometry for the assay of GNC in pharmaceuticals. Schelling et al. [4] have