CoFe2O4 nanoparticles modified carbon paste electrode for simultaneous detection of oxycodone and codeine in human plasma and urine

A rapid and sensitive electrochemical sensor for the simultaneous determination of oxycodone (OXY) and codeine (COD) has been proposed by utilizing the CoFe2O4 nanoparticles modified carbon paste electrode (CFCPE). The morphology and structure of CoFe2O4 nanoparticles (CFNPs) were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and FT-IR spectroscopy. Electrochemical characterization of the CFCPE was demonstrated with electrochemical impedance spectroscopy. The results indicated that CFCPE remarkably enhances the electrocatalytic activity of the electrode surface towards the oxidation of OXY and COD. The electrochemical oxidation of OXY and COD at the CFCPE was studied in detail using differential pulse voltammetry. The effect of various experimental parameters including pH, electrolyte composition and scan rate were investigated. At the optimum conditions, the concentration of OXY and COD were determined using DPV in a linear range of 0.06-38 μmol L−1 and a detection limit of 0.05 μmol L−1 and 0.02 μmol L−1, respectively. The proposed sensor exhibits a very fast response time (90 s) and good selectivity in the presence of Na+, K+, Ca2+, Mg2+, Cl−, NO3−, PO43−, SO42−, uric acid, citric acid, sucrose and glucose, uric acid, citric acid, sucrose, glucose, methadone and morphine. High stability, high sensitivity, and low detection limit made the proposed electrode applicable for the analysis of various real samples.