Development of a second type electrode based on the silver/silver ibuprofenate pair for ibuprofen quantification in pharmaceutical samples

Ibuprofen is a widely used pharmaceutical because of its therapeutic properties; it is considered a safe medicament, thus it does not require medical prescription to be sold. However, in order to ensure consumer's health it is indispensable that the pharmaceutical industry relies on analytic methods for its quantification. Potentiometry has proven to be a successful technique using second type electrodes, which in agreement with Nernst's equation can detect anions activity. On consideration of this, this research work presents the development of a second type electrode based on the silver/silver ibuprofenate pair. This involved modifying a pure silver wire using a sodium ibuprofenate solution, to obtain the redox pair. The following analytic parameters were obtained with the aid of the modified electrode: a sensitivity of -0.049 V decade [ibuprofenate]-1, 8 µmol L-1 for the detection limit and a quantification limit of 1.2 µmol L-1. The repeatability value in terms of the relative standard deviation was 5.9%. After performing an interferences analysis using some ions and excipients, it was corroborated that there were none, thus allowing appropriate quantification on a real sample.