Recyclable magnetic HNTs@MIPs-Based SERS sensors for selective, sensitive, and reliable detection of capsaicin for gutter oil discrimination

Abstract

Gutter oil, which poses a serious threat to human health and has generated widespread attention in recent years, is misused as cooking oil, creating a major food safety concern. Capsaicin has been identified as a promising indicator for the detection of gutter oil. Hence, in this study, we introduce a novel hybrid approach for capsaicin detection that combines magnetic molecular imprinting (MMIP) with surface-enhanced Raman scattering (SERS) technology to rapidly and accurately identify gutter oil. A magnetic molecularly imprinted polymer is developed with the incorporation of purified halloysite nanotubes, which provide a large specific surface area. The resulting product, magnetic halloysite molecularly imprinted polymers (MHNTs@MIPs), serves as a specific isolation material for the enrichment of capsaicin from complex matrices. The Ag NPs@Si (silver nanoparticles deposited on a silicon wafer surface) and Au NPs (gold nanoparticles), known for their excellent signal enhancement capabilities, work synergistically as the SERS substrate. Substantially enhanced SERS peaks are observed at 1173 cm⁻¹, indicating the potential of this method for capsaicin detection and gutter oil identification. A strong log-linear relationship between SERS intensity and the logarithm of capsaicin concentration is established across a wide range of 0.05–100 μM, with a detection limit of 67.7 nM. Furthermore, for both simulated and real gutter oil samples, capsaicin recovery rates of 95.5%–110.3% and 96.3%–104.9% were achieved using the SERS sensor, demonstrating good consistency with certified high-performance liquid chromatography (HPLC) results. Therefore, this SERS sensor can be served as efficient method for detecting capsaicin and monitoring oil quality.