Reverse-Phase HPLC Analysis of the Antiviral Drug, 9-[1,3-Dihydroxy-2-Propoxy Methyl] -Guanine (DHPG), with Amperometric Detection

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Abstract
The electrochemical activity of purine derivatives forms the basis for a sensitive and selective LCEC assay for an antiviral analog of deoxyguanosine. This report describes a reverse-phase chromatographic method with amperometric detection and an electroactive internal standard (tyrosine) for analyzing 9-[1,3-dihydroxy-2-propoxy)methyl]guanine (DHPG) in a parenteral dosage form. Using a glassy carbon electrode at +1.2 V vs. Ag/AgCl and a 25-cm 5 μm C18 column, a linear current-concentration dependence was obtained for DHPG between 25 ng/mL and 250 ng/mL, with a detection limit below 0.2 ng (S/N = 2). Statistical validation of the method showed good recovery efficiency and reproducibility. Parallel analyses of partially degraded DHPG solution samples by LCEC and by a cation-exchange chromatographic system with 254-nm detection demonstrated statistically equivalent estimations of the DHPG degradation rate constant. The general utility of the electrochemical detection technique was further demonstrated by the response linearity for another antiviral nucleoside, acyclovir. Our results demonstrate the versatility of reverse-phase HPLC with electrochemical detection for accurate, specific, and reliable analysis of purine-related therapeutic agents.