The development of fast, simple and reliable methods is necessary to monitor the quality of manufactured pharmaceuticals [1]. Herein, a cheap, fast, and sensitive disposable electrochemical sensor for paracetamol based on a graphite paper modified with the electrochemical deposition of functionalized multi-walled carbon nanotubes (GP@MWCNTCOOH) has been introduced. The modified electrode was characterized by field emission scanning electron microscope, electrochemical impedance spectroscopy, and cyclic voltammetry methods. Several influential parameters including the pH of supporting electrolyte, type of supporting electrolyte, the exposure time of the electrode to paracetamol, the duration of the electrochemical deposition of MWCNT-COOH, the concentration of MWCNT-COOH suspension, and the potential of deposition step were optimized. The calibration curve was constructed using linear sweep voltammetry method in the concentration range of 0.1 to 200 µM of paracetamol, which showed to be linear in the range of 1 to 100 µM. The limits of detection (LOD) and quantification (LOQ) were obtained to be 0.4 and 1 µM, respectively; and the sensitivity of the method was 0.4072 µA/µM. Moreover, the precision of the method in terms of relative standard deviation (%RSD) was achieved to be 3% (reproducibility) and 4% (reproducibility). Finally, the amount of paracetamol in some pharmaceutical products involving suppositories, tablets, syrup and oral drops was measured, and the recovery results in the range of 96%-104% were obtained. The sensor presents some important merits such as simplicity, the use of a cost-effective electrode substrate, the capability of miniaturization and being flexible, as well as the possibility of mass production.

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