The possibility of using pyrolyzed paper as disposable working electrodes for trace metals determination is reported for the first time. A small piece of pyrolyzed paper (0.7×0.7cm) was positioned at the bottom side of the electrochemical cell using a rubber O-ring, which defined the electrode area (0.48cm; 0.18cm). A large number of electrodes can be obtained from a single piece of standard dimensions (2.5cm×7.5cm) of paper, therefore minimizing the cost per unit. The electrochemical performance of the pyrolyzed paper was demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy and by the determination of Zn, Cd, and Pb by square-wave anodic stripping voltammetry. The unmodified pyrolyzed paper showed excellent performance for Pb and Cd detection (LOD =0.19 and 0.16 ppb, respectively). In the presence of Bi(in-situ film formation), the simultaneous determination of Zn, Cd and Pb was also possible (LOD=0.26, 0.25, and 0.39 ppb, respectively).

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FAST SIMULTANEOUS DETERMINATION OF PROPIFENAZONE, PARACETAMOL AND CAFFEINE USING BATCH INJECTION ANALYSIS WITH AMPEROMETRIC DETECTION. A fast and simple procedure for simultaneous determination of propyphenazone (PRO), paracetamol (PAR) and caffeine (CAF) was performed using batch injection analysis with multiple pulse amperometric detection (BIA-MPA). Three potentials pulses were selected for the analysis: +0.90 V/50 ms: only PAR was oxidized; +1.20 V/50 ms: oxidation of PAR and PRO without the interference of CAF; +1.60 V/50 ms: oxidation of the three compounds (PAR, PRO and CAF). The sample aliquot (150 μL) was directly injected onto the boron-doped diamond (BDD) electrode immersed in a BIA cell. The analytical characteristics of the proposed method include high analytical frequency (75 injections per hour), good stability (RSD < 3.9%; n = 10), and low detection limits (0.3, 0.2 and 0.1 mg L −1 for PRO, PAR and CAF, respectively). The proposed method yielded similar results to those obtained by liquid chromatography at a 95% confidence level.

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