Simultaneous electrochemical determination of dopamine and 5-hydroxyindoleacetic acid in urine using a screen-printed graphite electrode modified with gold nanoparticles.

The authors describe a disposable screen-printed graphite electrode (SPGE) modified with gold nanoparticles (AuNPs). The electrode, designated as AuNPs-SPGE, was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The AuNPs-SPGE combines the electrochemical features of graphite and the disposability of screen-printed electrodes. It displays excellent electrocatalytic activity towards dopamine (DA) and 5-hydroxyindoleacetic acid (5-HIAA). Two well-defined, sharp, and fully resolved voltammetric peaks (at 525 mV for DA and at 415 mV for 5-HIAA, both vs. Ag/AgCl) were found. Square wave voltammetry was used to simultaneously determine DA and 5-HIAA in mixtures and in urine. The linear working range extends from 0.1 to 120.0 μM for both DA and 5-HIAA, and the limits of detection (based on 3× the baseline noise) are 14.0 and 5.7 nM, respectively. The fabrication method for the AuNPs-SPGE is highly reproducible. The performance of the AuNPs-SPGE was evaluated by analyzing spiked human urine, and the recoveries were found to be well over 94.0 % for both compounds. These results indicate that the AuNPs-SPGE represents a highly selective and sensitive sensor for simultaneous determination of DA and 5-HIAA in urine. Graphical Abstract Fabrication, characterization and electrochemical behavior of gold nanoparticles modified screen-printed graphite electrode towards dopamine and 5-hydroxyindoleacetic acid in human urine.