Enhanced voltammetric detection of chlorogenic acid using a GCE modified with CNTs and ultrasonically assisted synthesized ZrO2 and W nanoparticles: Application to traditional coffee samples

Abstract

The increasing demand for antioxidant-rich coffee emphasizes the need for sensitive, reliable methods to detect chlorogenic acid (CGA), a key antioxidant in coffee. Accurate CGA quantification is challenging due to variations across different coffee types and preparation methods, posing difficulties for conventional analytical techniques. This study introduces a novel electrochemical platform for CGA detection, utilizing a composite of zirconium oxide (ZrO₂), tungsten (W) nanoparticles, and carbon nanotubes (CNT). The composite was applied to a glassy carbon electrode (GCE) via drop-casting, followed by electrochemical characterization using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The impedance data were interpreted using a R_s + (R_ct + (W‖C₁)) + C₂ equivalent circuit, revealing a low charge transfer resistance and favorable interfacial properties. The developed sensor was used to detect CGA in bitter, Turkish, and turpentine coffee samples via square wave voltammetry (SWV). The ZrO₂@W/CNT/GCE sensor exhibited high performance with an electroactive surface area of 0.368 cm², low charge transfer resistance (113 Ω), a broad detection range (4.0 × 10⁻¹⁰ to 5.0 × 10⁻⁶ M), and a low detection limit (1.4 × 10⁻¹¹ M). It accurately quantified CGA levels in coffee samples: 46.9 ± 0.9 mg/L in bitter coffee, 36.1 ± 0.5 mg/kg in Turkish coffee, and 43.3 ± 0.8 mg/kg in turpentine coffee. The platform demonstrated excellent reproducibility, stability, and selectivity, showing potential for reliable CGA detection in coffee analysis.