High Selective Methadone Sensor Based on Molecularly Imprinted Polymer Carbon Paste Electrode Modified with Carbon Nanotubes

We demonstrate here a novel carbon paste electrode approach able to determine methadone in physiological samples without the need of sample pre-treatment. The selective carbon paste electrode based on molecularly imprinted polymer is modified with multi wall carbon nanotubes. The molecularly imprinted polymer is used as a recognition element in the carbon paste electrode structure and the multi wall carbon nanotubes are incorporated in the structure of carbon paste electrode to improve both the conductivity and the transduction of the composite. In this method, methadone is firstly extracted from the sample into the sensor and subsequently the extracted methadone amount is determined by differential pulse voltammetry. The selective molecularly imprinted polymer cavities for methadone are prepared by bulk polymerization technique. Methadone is used as a template in the polymerization step. This polymer is characterized on the basis of fourier transform infrared spectroscopy and thermal analysis. The sensor is characterized in terms of carbon paste electrode composition. Furthermore, extraction step is optimized respect to pH, sample matrix, stirring rate and extraction time. An optimum electrochemical response is obtained for differential pulse voltammetry method in 0.1 mol.L-1 phosphate buffered solution at pH 7. The electrode shows a wide dynamic linear range for methadone from 10(-7) to 10(-2) mol.L-1. The observed detection limit and RSD are 10(-8) mol.L-1 and 1.5%, respectively. Finally, the proposed method is applied for the determination of methadone in urine and medicinal tablet.