Simultaneous voltammetric detection of ascorbic acid, dopamine and uric acid using a pyrolytic graphite electrode...

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Biosensors

Background:

• Simultaneous detection of neurotransmitters and biomolecules is challenging due to interference and electrode fouling.
• Pyrolytic graphite electrodes (PGE) are promising platforms for electrochemical sensing.
• Developing selective and sensitive electrochemical methods for detecting dopamine (DA), ascorbic acid (AA), and uric acid (UA) is crucial for biomedical applications.

Purpose of the Study:

• To develop a modified pyrolytic graphite electrode for the simultaneous and selective detection of dopamine, ascorbic acid, and uric acid.
• To investigate the role of pH in the electrode modification process and its impact on detection performance.
• To evaluate the applicability of the developed sensor for analyzing biological samples.

Main Methods:

• Electrode modification via a two-step anodization process in NaOH and dopamine solutions.
• Electrochemical characterization using cyclic voltammetry.
• Simultaneous detection of dopamine, ascorbic acid, and uric acid at different pH levels.
• Determination of detection limits and sensitivities.
• Analysis of uric acid in human urine, blood, and serum samples.

Main Results:

• A stable melanin polymeric film was formed on the PGE surface, preventing electrode poisoning.
• Effective simultaneous detection of AA, DA, and UA was achieved with significant peak potential differences (ΔE(AA-DA)=222 mV, ΔE(AA-UA)=360 mV, ΔE(DA-UA)=138 mV).
• Low detection limits were obtained: 1.4x10⁻⁶ mol L⁻¹ for UA, 1.3x10⁻⁵ mol L⁻¹ for AA, and 1.1x10⁻⁷ mol L⁻¹ for DA.
• High sensitivities were reported: 7.7±0.5 A mol⁻¹ cm⁻² for UA, 0.061±0.001 A mol⁻¹ cm⁻² for AA, and 9.5±0.05 A mol⁻¹ cm⁻² for DA.
• Uric acid was successfully quantified in human biological samples (urine, blood, serum) with high recovery rates (92-102%) and no matrix effects.

Conclusions:

• The developed modified pyrolytic graphite electrode offers a robust and selective platform for the simultaneous electrochemical detection of dopamine, ascorbic acid, and uric acid.
• The pH-dependent melanin film formation is key to preventing electrode fouling and enabling sensitive detection.
• The sensor demonstrates excellent potential for practical applications in clinical diagnostics and biological sample analysis without extensive sample preparation.