Investigation of the electrochemical properties of entacapone and tolcapone drugs used in the treatment of parkinson disease and development of a method for voltammetric determinations

Parkinson's disease is a chronic, slow progressive and important brain disease that follows with the loss of nerve cells. Entacapone (ENT and tolcapone (TOL) are synthetic drugs and are used in the treatment of Parkinson's disease. This research involves the electroanalytical analysis of ENT and TOL on the surface of a boron-doped diamond electrode that has been subjected to electrochemical cathodic pretreatment using cyclic voltammetry and square-wave (SW) voltammetry techniques. The study explored how peak current and potential are influenced by several experimental variables, including scan rate, pH, SW parameters, and other factors. The SW voltammetric technique was applied to determine ENT in a H2SO4 solution, achieving a linear dynamic range from 1.0 to 40.0 μg mL-1 (3.3 x 10-6-1.3 x 10-4 M, vs. Ag/AgCl), with a detection limit of 0.25 μg mL-1 (8.2 x 10-7 M). For TOL, using the same technique in a 0.1 M phosphate buffer solution (pH 2.5), a positive linear response was observed at +0.66 V (vs. Ag/AgCl), with a range from 1.0 to 50.0 μg mL-1 (3.7 x 10-6 - 1.8 x 10-4 M) and a detection limit of 0.29 μg mL-1 (1.1 x 10-6 M). This methodology has proven effective for quantifying ENT and TOL in pharmaceutical preparations.