Voltammetric Detection of Vanillylmandelic Acid and Homovanillic Acid Using Urea-Derivative-Modified Graphite...

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Computational Chemistry

Background:

• Vanillylmandelic acid (VMA) and homovanillic acid (HVA) are key diagnostic markers for neuroblastoma.
• Accurate detection of VMA and HVA is crucial for early diagnosis and monitoring of neuroblastoma.

Purpose of the Study:

• To elucidate the mechanism behind the selective discrimination of VMA and HVA using a urea-derivative-modified graphite electrode.
• To understand the interactions between the electrode surface and these structural analogues at a molecular level.

Main Methods:

• Density Functional Theory (DFT) calculations to model binding sites and interactions.
• Fourier-Transform Infrared (FTIR) spectroscopy to analyze surface modifications and analyte binding.
• Electrochemical impedance spectroscopy (EIS) to study interfacial properties.
• Differential Pulse Voltammetry (DPV) for quantitative detection.

Main Results:

• DFT calculations identified optimal binding sites and revealed differences in analyte interactions.
• FTIR analysis indicated variations in NH vibrations, suggesting different orientations of the urea moiety for carboxylate discrimination.
• A stronger hydrogen-bonding interaction was observed with the more basic anion (VMA).
• The modified electrode successfully detected VMA and HVA individually at a concentration of 1.99 × 10⁻⁵ M with good recovery and precision.

Conclusions:

• The urea-derivative-coated graphite electrode effectively discriminates between VMA and HVA based on their chemical properties.
• The study provides molecular-level insights into the electrochemical sensing mechanism.
• This approach offers a promising method for the sensitive detection of neuroblastoma biomarkers.