Determination of Codeine in Human Plasma and Drug Formulation Using a Chemically Modified Electrode

Both flow injection methodology and square-wave voltammetry were developed and evaluated for determining codeine in human plasma and pharmaceutical formulations using a Nafion/ruthenium oxide pyrochlore chemically modified electrode. Combining the electrocatalytic function of the ruthenium-oxide pyrochlore with charge-exclusion and the preconcentration features of Nafion perform well in codeine detection. Compared to a bare glassy carbon electrode, the chemically modified electrode exhibits a shift of the oxidation potential in cathodic direction and a marked enhancement of the current response. A linear calibration plot is obtained over the 0–32 μM range in 0.05 M HClO4 solution with a detection limit (3σ) of 10 nM in the square-wave voltammetric method. While, in flow-injection analysis, a linear calibration plot is obtained over the 0.5–40 μM range with a detection limit of 0.86 ng. Quantitative analysis was performed by the standard addition method for codeine content in human plasma and a commercially available drug.