Simultaneous determination of dopamine and cysteamine by flow injection with multiple pulse amperometric detection using a boron-doped diamond electrode

A flow injection analysis (FIA) system with multiple pulse amperometric (MPA) detection was proposed for the simultaneous determination of dopamine (DOP) and cysteamine (CYS) using a cathodically pre-treated boron-doped diamond electrode (CPT-BDD). The electrochemical behaviors of DOP and CYS were evaluated by cyclic voltammetry in a potential range from 0 to 1.7 V at a scan rate of 0.05 V s(-1) using 0.05 mol L-1 H2SO4 as supporting electrolyte. Two oxidation peaks were observed during anodic potential scanning, at potentials of 0.8 V (DOP) and 1.6 V (CYS). Under optimized experimental conditions, such as potentials E-1 = + 0.8 V 100 ms(-1) (pulse potential at which DOP was oxidized) and E-2 = + 1.6 V 200 ms(-1) (pulse potential at which both analytes were oxidized), the analytical curves were linear in the concentration ranges from 5.0 x 10(-7) to 1.3 x 10(-4) mol L-1 for DOP and from 5.0 x 10(-7) to 1.5 x 10(-4) mol for CYS, with detection limits of 1.1 x 10(-8) and 1.3 x 10(-8) mol L-1, respectively. The BDD sensor showed good sensitivity, stability and repeatability (analytical frequency of 165 determinations per hour), and no interference in the electrochemical determination of these analytes in the presence of other compounds. The proposed method was successfully applied using the FIA-MPA method in river water and serum samples, with recoveries close to 100%.