Sensitive determination of caffeoylquinic acid in food and blood samples using nanostructured conducting polymer...

3-Caffeoylquinic acid (3-CQA), a prominent phenolic acid, plays a critical role in glucose metabolism and is associated with the prevention of type-2 diabetes. The selective and sensitive detection of 3-CQA remains challenging due to interferences from substances such as caffeine (CAF) and the instability of signals from unmodified electrodes. To address this, this study developed a nanostructured conducting polymer composite based on acid-functionalized multi-walled carbon nanotubes (FMWCNTs) and 3-amino-5-mercapto-1,2,4-triazole (AMTa), which was integrated onto a glassy carbon electrode (GCE) for the selective detection of 3-CQA. The composite electrode (GCE/OD/FMWCNTs/p-AMTa) was thoroughly characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and electrochemical analysis. In contrast to the unmodified GCE, which fails to maintain a stable voltametric profile for 3-CQA detection due to the deposition of its oxidation products, the composite-modified electrode demonstrates a stable electrochemical response, with a fourfold increase in the catalytic oxidation current. This improvement is attributed to the strong electrostatic and hydrogen-bonding interactions between the heteroatoms in the polymer backbone of p-AMTa and 3-CQA, as well as the π-π interactions between FMWCNTs and the aromatic ring of 3-CQA. Additionally, selective determination of 3-CQA is achieved even in the presence of 500 times the concentration of CAF. The amperometric i-t curve exhibits a significant increase in response to 3-CQA concentrations ranging from 0.1 to 200 μM, with a detection limit (LOD) of 30 nM (S/N = 3). The proposed sensor demonstrates excellent performance in detecting 3-CQA in blood, coffee, tea, and various food samples, yielding satisfactory recovery results.