Determination of diclofenac using electromembrane extraction coupled with stripping FFT continuous cyclic voltammetry

•Electro membrane extraction (EME) was combined with FFT voltammetry technique.•The method was used for on-line determination of diclofenac in whole blood samples.•Low limit of detection and a wide linear range were achieved.•EME-SFFTCCV enhances the lifetime of electrode and reduces its surface poisoning.•This method reduces time consuming sequences of the sample preparation step.

For the first time, on-line and ultra-sensitive determination of trace amount of diclofenac in whole blood sample was performed by coupling of electromembrane extraction (EME) and stripping fast Fourier transform continuous cyclic voltammetry (SFFTCCV). In SFFTCCV, the potential waveform was continuously applied on a carbon paste electrode and the electrode response was obtained by subtracting the background current and integrating the current in potential range of the analyte oxidation. A central composite design was used for the optimization of the parameters influencing the extraction efficiency. By applying a DC potential of 20 V during 28 min of extraction, diclofenac was migrated from the sample solution (pH 5), into a thin layer of 1-octanol immobilized in the pores of a porous flat sheet membrane and then into the acceptor solution (pH 7). The method presented a good linearity within the range of 5-1000 ng mL−1 with a determination coefficient of 0.993 in whole blood samples. Limits of detection (LOD) and quantification (LOQ) were found to be 1.0 ng mL−1 and 5.0 ng mL−1 respectively.

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