Development of Electrochemical Sensors and Their Application in Environmental and Clinical Analysis

Abstract

Electrochemical sensors were developed for the determination of hydroxylamine in environmental monitoring and the simultaneous determination of dopamine, uric acid, and glucose in clinical analysis. Two projects were undertaken. The first project reports the development of an electrochemical sensor for the detection of hydroxylamine by flow injection amperometry based on a glassy carbon electrode (GCE) modified with a nanocomposite of palladium nanoparticles and glassy carbon spheres (PdNPs-GCS). The surface morphology and electrochemical behavior of hydroxylamine on the PdNPs-GCS modified electrode were characterized by scanning electron microscope and cyclic voltammetry, respectively. The amount of PdNPs-GCS used to modify the electrode, the working potential, the sample volume and the flow rate were optimized. Under the optimal conditions, this sensor provided a wide linear concentration range of 25 to 25,000 μM. The limit of detection (LOD) and the limit of quantitation (LOQ) were 36 μM and 120 μM, respectively. Moreover, it provided good stability (%RSD <5.3 (n=73)). The second project involved the development of a novel electrochemical sensor using a system of dual working electrodes for the simultaneous determination of glucose, uric acid and dopamine. A graphene oxide-modified glassy carbon electrode (GO/GCE) was fabricated and used with adsorptive anodic stripping voltammetry to detect uric acid and dopamine while a chitosan/glucose oxidase/prussian blue-graphite modified glassy carbon electrode (Chi/GOx/PB-G/GCE) was fabricated and used for chronoamperometric glucose detection. The fabrication and operating conditions for both electrodes were optimized. Linearity was obtained in the ranges of 0.10 to 30 μM and 30 to 80 μM for dopamine, 0.20 to 10 μM and 10 to 30 μM for uric acid and 15 to 1,500 μM for glucose. The system provided detection limits (LOD 3G/S) of 0.080 μM, 0.11 μM, and 5.7 μM for dopamine, uric acid and glucose, respectively. This dual working electrode system showed good reproducibility and excellent recovery for the simultaneous determination of dopamine, uric acid, and glucose. When used to analyze dopamine, uric acid, and glucose in blood plasma samples, the results agreed well with those from conventional methods (P>0.05), confirming the potential of this system to simultaneously determine these three analytes in real samples.