Simultaneous determination of caffeine and acetaminophen in drug formulations by square-wave voltammetry using a chemically modified electrode

A Nafion®/ruthenium oxide pyrochlore chemically modified electrode was used for the simultaneous determination of caffeine and acetaminophen in drug formulations by square-wave voltammetry. Compared to a bare glassy carbon electrode, the chemically modified electrode exhibits an apparent shift of the oxidation potentials in the cathodic direction and a marked enhancement in the current responses for both caffeine and acetaminophen. Linear calibration curves are obtained in 0.05 M perchloric acid, the supporting electrolyte, over 10–250 and 5–250 μM for caffeine and acetaminophen, respectively. The detection limits (3σ) are 2.2 and 1.2μM for caffeine and acetaminophen, respectively. The practical analytical utility is illustrated by selective measurements of caffeine and acetaminophen in several commercially available drugs, without any preliminary treatment.