A novel electrochemical imprinted sensor was constructed for sensitive and selective determination of tramadol (TRA) by combination of a functionalized multiwall carbon nanotubes (f-MWCNTs) layer and a thin molecularly imprinted film. The imprinted sensor was fabricated on the surface of a glassy carbon electrode (GCE) through layer by layer modification of f-MWCNTs and a thin film of molecularly imprinted polymer (MIP) composed of polypyrrole (PPy), sol–gel and tramadol by electrochemical deposition. Multi wall carbon nanotubes (MWCNTs) were introduced for the enhancement of electronic transmission and sensitivity. Electrochemical methods including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the processes of electropolymerization, template removal and rebinding in the presence of [Fe(CN)6]3−/[Fe(CN)6]4−which was used as an electrochemical active probe. The effect of several parameters influencing the performance of the imprinted sensor, were investigated and optimized. Under the optimized experimental conditions, the calibration curve of the MIP electrode had two linear concentration ranges from 0.2 to 2.0 nM and 2.0–20.0 nM, with a limit of detection (LOD) of 0.03 nM. The effects of interfering substances on the determination of tramadol were also investigated and it was found that the proposed sensor is highly selective to tramadol. Also, the reproducibility, repeatability, stability and the response time of the imprinted sensor were all found to be satisfactory. Finally, the constructed electrode was successfully employed for determination of tramadol in real samples.

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