Terahertz metamaterial sensor-based detection of procymidone and chlorpyrifos residues in Ligusticum chuanxiong

Pesticide residues in Traditional Chinese Medicine (TCM) have raised significant concerns due to their potential health risks. Conventional pesticide residues detection methods are often limited by prolonged detection times and complex sample pretreatment procedures. Therefore, developing a rapid and highly sensitive method for pesticide residue detection is essential. In this paper, we present a terahertz (THz) metamaterial sensor for rapid detection of trace procymidone and chlorpyrifos residues in Ligusticum chuanxiong. The sensor exhibits a theoretical sensitivity of 360 GHz/RIU and offers a minimum detectable level of 1 μg/L, while the entire workflow can be completed within 30 min. Based on the THz metamaterial sensor, quantitative concentration-frequency shift models for chlorpyrifos and procymidone in organic Ligusticum chuanxiong were established (fitting coefficient R² > 0.98). These models, combined with the proposed Leave-One-Out Cross-Validation (LOO-CV) based calibration method, were applied to the detection of pesticide residues in commercial Ligusticum chuanxiong. The final average prediction error was approximately 3.8%, providing a novel and rapid testing solution for the quality control of TCM.