A Simple Strategy for Simultaneous Determination of Paracetamol and Caffeine Using Flow Injection Analysis with Multiple Pulse Amperometric Detection

Abstract

In this work, we report a simple and novel strategy for simultaneous analysis using flow injection analysis with multiple pulse amperometric (FIA-MPA) detection. The proposed strategy was successfully used for simultaneous determination of paracetamol and caffeine (model analytes) in pharmaceutical formulations. A sequence of potential pulses (waveform) was selected in such a way that PA is selectively oxidized at E 1 (+ 1.20 V/50 ms) and both compounds (PA + CA) are simultaneously oxidized at E 2 (+ 1.55 V/50 ms); hence, current subtraction (using a correction factor) can be used for the selective determination of CA. The proposed FIA method is simple, cheap, fast (140 injections h À1), and present selectivity for the determination of both compounds in pharmaceutical samples, with results similar to those obtained by HPLC at a 95 % confidence level.

Batch‐injection Analysis Better than ever: New Materials for Improved Electrochemical Detection and On‐site Applications

“…The current from the compound that was only detected in the second potential pulse can be obtained through subtraction between the current signals at the two amperograms. This was possible using a correction factor , a strategy used before for simultaneous analysis in flow injection analysis with amperometric detection. The simultaneous determinations were possible for the compounds in three different samples without using chemometric calibration techniques or separation based methods (chromatography or capillary electrophoresis).…”

Fast and Selective Simultaneous Determination of Acetaminophen, Aspirin and Caffeine in Pharmaceutical Products by Batch Injection Analysis with Multiple Pulse Amperometric Detection

“…ASA exhibits anodic peak currents from + 1.5 V up to 1.8 V and an abrupt increase up to +2.3 V (studied interval). The obtained irreversible oxidation of these compounds over cathodically pre‐treated BDDE in acid media has already been observed using DPV and MPA detection . The oxidation mechanisms on carbon electrodes proposed in literature involve a transfer of 2‐electron and 2‐proton for PA , 4‐electron and 4‐proton for CA , 1‐electron and 1‐proton for SA and 2‐electron and 1‐proton for ASA .…”

“…Moreover, CF 1 and CF 2 are becoming closer to a unity when 300 μL are injected, as PA presents maximum peak signals in all applied pulses (CF 1 and CF 2 values were coherent with the electrochemical behaviour of PA using this volume). Volumes higher than 300 μL were not evaluated due to the contamination of the BDDE surface and decrease the sampling rate . Thus, an injection volume of 300 μL was chosen in the further experiments.…”

“…As presented, the higher flow rates provided the greater currents (Figure a, 4b and 4f) due to decreasing of the Nernst diffusion layer and poor precision and accuracy, considering that the sample zone passes quickly over the BDDE surface (acquisition of few points in the current plateau ). Low accuracy was also observed when using high stirring rates of the solution inside the BIA cell (Figure b, 4c and 4e) due to excessive dispersion of the sample zone (between pipette tip and BDDE surface) promoted by the high convection of the electrolyte .…”

“…Multiple Pulse Amperometry (MPA) technique apply from two to ten fast sequential potential pulses over the working electrode an shows the results as an independent amperogram for each pulse, which offers more analytical possibilities than classical amperometry, as: (a) improved reproducibility by applying additional potential for cleaning and/or activation pulses or by the ratio among signals of analyte and an internal standard ; (b) better selectivity by monitoring of analyte (or a redox product) in a pulse without interferers ; (c) verification of purity of an API in pharmaceutics ; (d) acquisition of a electrochemical profile (fingerprint) for drug screening ; (e) simultaneous determination of two or three species using one sensor. BDDE has been was used in most cases because combine smaller adsorption of organic compounds, wide potential window (up to 3 V) and lower capacitive currents in comparison with other solid electrodes .…”