Nanostructured conducting molecularly imprinted polypyrrole based quartz crystal microbalance sensor for naproxen determination and its electrochemical impedance study

This paper represents a naproxen (NAP) imprinted nanostructured conducting molecularly imprinted polypyrrole (CMIP) film which is electrochemically synthesized on a quartz crystal microbalance (QCM) gold electrode and electrochemically overoxidized for increasing its selectivity as a recognition element of a QCM sensor for the detection of NAP. It was shown that the selectivity of the obtained film toward NAP was enhanced by controlled overoxidation. The characteristics of CMIP and overoxidized (OCMIP) films were investigated by ATR FT-IR, cyclic voltammetry and electrochemical impedance spectroscopy (EIS), and the morphology and coverage of the film were studied by FE-SEM. Parameters of cyclic voltammetric preparation of the CMIP film including the potential range, scan rate, number of cycles (film thickness) and the effect of surfactant on polymer film growth were optimized. The overoxidation condition including overoxidation potential, number of cycles and pH and type of electrolyte solution were studied and optimized. It was found that the excessive overoxidation of CMIP film would cause two unwanted effects on the sensor; first the loss of sensor regeneration in repeated uses, and second, the decrease of the cohesion of film on the gold electrode. Thus the amount of overoxidation of the film was controlled very carefully to obtain the best selectivity with minor loss of film cohesion and sensor reproducibility. This aim was satisfied by the aid of impedimetric study of the film before and during the overoxidation. Results obtained from the QCM and impedance measurements show that overoxidized NAP imprinted CMIP could be used for determination of NAP in aqueous media with a limit of detection of 0.04 mu mol L-1 and RSD = 4.9% (n = 5). The proposed sensor offers a good selectivity and cost effective properties for fast determination of NAP with ease of preparation and simple instrumentation.