Electrochemical determination of HIV drug Abacavir based on its reduction

Abacavir (I), a drug used in the treatment of HIV, is electrochemically reduced at the dropping mercury electrode in a four-electron process, similar to structurally related adenine (III) and adenosine triphosphate (IV). To undergo the reduction, the species is protonated in the vicinity of the electrode. The protonations take place on the 6-amino group and on one of the pyrimidine ring nitrogens. The role of covalent hydration of the pyrymidine ring has been interpreted. Best suited as supporting electrolytes for analytical purposes are solutions of 0.1-1.0 M sulfuric, perchloric, or hydrochloric acids. Procedures of analyses of tablets containing I were established and validated, based on peak currents obtained by linear sweep, differential pulse, or square-wave voltammetry with a hanging mercury drop electrode as indicator electrode. The procedure proved to be more sensitive and more reliable than that based on oxidation on a glassy carbon electrode, proposed previously.