Ibuprofen [2- (p-isobutyl phenyl) propionic acid] is a nonsteroidal anti-inflammatory drug (NSAID) with high analgesic, antipyretic and anti-inflammatory properties. Due to its effectiveness in pain, fever and inflammation treatment, and its easy acquisition by consumers (it does not requires medical prescription), it has become one of the most consumed NSAIDs in the world (Bushra & Aslam, 2010). Recently, Sondergaard et al. (2017) reported heart diseases related to ibuprofen consumption in high and frequent doses; therefore, the quantification of this active compound in medicines has become a matter of great importance.
The United States Pharmacopoeia (USP-NF-26) and the European Pharmacopoeia (EP) establish official methodologies to carry out the quantification of these drug, however, these have some disadvantages compared to electroanalytical techniques, such as high analysis times and costs, previous pretreatment of the sample and more complicated procedures.
Among the electroanalytical techniques used to quantify drugs, voltammetry with carbon paste electrodes has demonstrated outstanding results, since these electrodes present important advantages compared to others. Carbon paste electrodes can be easily modified, due to the inclusion of nanostructures in order to improve the electrochemical transformation of electroactive molecules (Ramírez, 1996).
Metal oxide nanoparticles have been recently widely used for the modification of electrodes, due to its high catalytic activity, in which indirectly improves the analytical signal. Copper oxide nanoparticles have aroused great interest since they can be easily synthesized at a low cost, in addition to having a great catalytic activity, (Male et al., 2004).
Taking into account these advantages, this work presents the development of a voltammetric methodology based on a graphite-CuO nanoparticles paste electrode, optimized by the Box-Behnken method, in order to quantify ibuprofen. Cetyl trimethyl ammonium (CTAB) is used to improve the analytical signal of the proposed methodology.
Methodology
As part of the electrochemical characterization of the system, Cyclic Voltammetries were carried out to determine the electrochemical behavior of ibuprofen, optimize the pH medium, optimize the supporting electrolyte and optimize the working electrode’s composite composition
As part of the analytical characterization, Differential Pulse Voltammetry (DPV) was optimized using a Box-Behnken design in order to maximize the analytical signal. Calibration curves are used to determine the analytical parameters of the proposed methodology, the effect of possible interferences in the system is evaluated. The proposed methodology is then used for the quantification of ibuprofen in commercial drugs and validated with the official methodology.
Results
By means of cyclic voltammetry (CV), a composite mixture 99% graphite - 1% CuO nanoparticles could be established, using for the supporting electrolyte a mixture of 0.1 M phosphate buffer, 0.05 M of CTAB and 0.5 M of sodium sulfate with an optimum pH of 6.2. With CVs at different scan rates, it was possible to establish that the process governing ibuprofen oxidation of is diffusional.
Significant changes were observed in the electroanalytical signal for different ibuprofen concentrations in a range of 10-5 to 10-3 M. The resulting calibration curve showed two linear trends, one in the concentration range 10-5 to 10-4 M and the other from 10-4 to 10-3 M. The curve was constructed considering the optimal parameters of the DPV: step potential of 3 mV, pulse amplitude of 100 mV, pulse period of 100 ms and a pulse width of 80 ms, according to the Box Behnken design.
References
Bushra, R. y Aslam, N. (2010). An overview of clinical pharmacology of ibuprofen. Oman Medical Journal, (25), 3, 155 – 161.
Sondergaard, K. B., Weeke, P., Wissenberg, M., Schjerning Olsen, A. M., Fosbol, E. L., Lipper, F. K., Torp-Pedersen C. Gislason G. H., Folke Fredrik (2017). Non-steroidal anti-inflamatory drug use is associated with increased risk of out-of-hospital cardiac arrest: a nationwide case-time-control study. European Heart Journal Cardiovascular Pharmacotherapy, (3), 2, 100-107.
Male, K. B., Hrapovic, S., Liu, Y., Wang, D., Luong, J. (2004), Electrochemical detection of carbohydrates using copper nanoparticles and carbon nanotubes. Analytica Chimica Acta 516 35–41.
T. Ramírez Silva, Diferentes electrodos composite con matriz de grafito. Estudio comparativo de su funcionamiento y de sus potencialidades, Tesis Doctoral, Universidad Autónoma Metropolitana-Iztapalapa (1996).