This work describes the coupling of a biomimetic sensor to a flow injection system for the sensitive determination of paracetamol. The sensor was prepared as previously described in the literature (M. D. P. T. Sotomayor, A. Sigoli, M. R. V. Lanza, A. A. Tanaka and L. T. Kubota, J. Braz. Chem. Soc., 2008, 19, 734) by modifying a glassy carbon electrode surface with a Nafion Ò membrane doped with iron tetrapyridinoporphyrazine (FeTPyPz), a biomimetic catalyst of the P450 enzyme. The performance of the sensor for paracetamol detection was investigated and optimized in a flow injection system (FIA) using a wall jet electrochemical cell. Under optimized conditions a wide linear response range (1.0 Â 10 À5 to 5.0 Â 10 À2 mol L À1 ) was obtained, with a sensitivity of 2579 (AE129) mA L mmol À1. The detection and quantification limits of the sensor for paracetamol in the FIA system were 1.0 and 3.5 mmol L À1 , respectively. The analytical frequency was 51 samples h À1, and over a period of five days (320 determinations) the biosensor maintained practically the same response. The system was successfully applied to paracetamol quantification in seven pharmaceutical formulations and in water samples from six rivers in São Paulo State, Brazil.

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Real-time monitoring of the electrochemical degradation of acetaminophen was performed using a biomimetic sensor coupled to a flow injection analysis (FIA) system. Degradation of the drug was carried out at constant current density (24 to 180 mA cmTwo commercial DSA anodes (DSA-Cl 2 and DSA-O 2 ) were compared. The degradation process was monitored online using an amperometric sensor based on the biomimetic catalyst iron(III) tetrapyridinoporphyrazine (FeTPyPz), coupled to the degradation cell. The optimized FIA detection system employed the electrolyte solution as carrier, a flow rate of 1.25 mL min À1 and an injected sample volume of 75 mL. The real-time data obtained showed, as expected, that acetaminophen degradation followed pseudo-first order kinetics, with the DSA-Cl 2 anode showing a higher efficiency according to the calculated apparent rate constant values. The advantage of the proposed on-line system is that a larger number of points can be monitored in a shorter time compared to other off-line methods, which improves the accuracy of estimates of electrochemical degradation constants.

This paper reports, for the first time, the online monitoring to the electrochemical degradation of the paracetamol using a biomimetic sensor coupled to a Flow Injection Analysis (FIA) system. The electrochemical degradation of the drug was carried out in aqueous medium using a flow-by reactor with a DSA anode. The process efficiency was monitored at real time by the biomimetic sensor constructed by modifying a glassy carbon electrode with a Nafion membrane doped with iron tetrapyridinoporphyrazine (FeTPyPz). Simultaneously, we carried out off-line analysis by liquid chromatography (HPLC) during the experiments in order to validate the proposed system. In addition, to investigate the degradation products of the paracetamol electrolysis, we used the techniques of UPLC/MS and GC/MS.