Simultaneous Determination of Caffeine, Ibuprofen, and Paracetamol by Flow-injection Analysis with Multiple-pulse Amperometric Detection on Boron-doped Diamond Electrode

This work presents a simple, fast and low-cost method for the simultaneous determination of three drugs by flow-injection analysis with multiple-pulse amperometric (MPA) detection using a wall-jet flow cell with a boron-doped diamond electrode. The amperometric determination of caffeine (CF), ibuprofen (IB) and paracetamol (PC) was performed by the application of a four-potential waveform using the MPA technique. PC is oxidized at E-1 (1.20 V/70 ms) and thus selectively detected; PC and CF are oxidized at E-2 (1.49 V/40 ms); PC, CF and IB are oxidized at E-3 (1.70 V/70 ms); and E-4 (1.80 V/100 ms) is applied for electrode cleaning. The subtraction of currents obtained at the different potentials did not provide accurate determinations of CF and IB, thus it was required to investigate correction factors to determine CF and IB without the interference from PC and CF using the respective amperometric signals obtained at E2 and E-3. The proposed method was successfully applied for the determination of three drugs in pharmaceutical samples with low generation of residues and a high analytical frequency (150 h(-1)) in comparison with HPLC-DAD method.