Response Surface Methodology-Optimized QuEChERS Combined with Liquid Chromatography–Quadrupole-Time-of-Flight Mass Spectrometry for Simultaneous Screening of Pesticides and Mycotoxins in Astragalus

This study used the QuEChERS method in combination with liquid chromatography–quadrupole-time-of-flight mass spectrometry (LC-Q-TOF/MS) to develop a method for simultaneous detection of 187 pesticides and 10 mycotoxins in Astragalus. The samples were extracted using an acetonitrile–water solution containing 5% formic acid, and the amount of purification materials was optimized through response surface methodology. The results show that 197 compounds exhibit good linear relationships within their respective linear ranges (R2 > 0.995). The screening detection limits (SDLs) and the limits of quantification (LOQs) ranged from 0.001 to 0.02 mg/kg and 0.002 to 0.02 mg/kg, respectively. At the spiked levels of 1, 2, and 10 times LOQ, compound recoveries ranged from 61.5% to 118.9%, 67.1% to 119.6%, and 72.0% to 119.3%, respectively, with relative standard deviations (RSDs) all less than 20.0%. The intra-day precision and inter-day precision are less than 10% and 20%, respectively. This method was applied to detect 20 batches of commercially available Astragalus samples. Six compounds (three pesticides and three mycotoxins) were detected; the residues of aflatoxin and ochratoxin A in two batches exceeded the maximum residue limits and required attention. The established method is simple, rapid, and highly sensitive. It is also reproducible and meets the requirements for the accurate quantitative analysis of multiple pesticide residues and mycotoxins in Astragalus.