Simultaneous screening of pesticides and mycotoxins in dried goji berries and mulberries by QuEChERS-liquid chromatography-quadrupole-time of flight mass spectrometry

Goji berries and mulberries are susceptible to pest and pathogen invasion due to their high sugar content and the impact of growth environment. Their quality and safety are primarily influenced by pesticide residues and mycotoxins. This study has developed a simple， high-throughput， and sensitive analytical method for the simultaneous determination of 172 pesticides and 11 mycotoxins in the medicinal and edible substances of goji berries and mulberries using an improved QuEChERS method coupled with liquid chromatography-quadrupole-time of flight mass spectrometry （LC-Q-TOF/MS）. The sample was hydrated with 7 mL of purified water， and 10 mL of 5% formic acid in acetonitrile was added as the extraction solvent， along with 4 g of anhydrous MgSO₄ and 1 g of NaCl as extraction salts. The extract was purified using 400 mg of anhydrous MgSO₄， 150 mg of primary secondary amine （PSA）， 100 mg of octadecylsilane （C₁₈）， and 5 mg of multi walled carbon nanotubes （MWCNTs）. The supernatant was dried under nitrogen， and the residue was reconstituted in 1.0 mL of a methanol-water solution （3∶2， volume ratio）， homogenized by ultrasonication， and filtered through a 0.22 μm membrane prior to analysis. Separation was performed on a ZORBAX SB-C₁₈ column （100 mm×2.1 mm， 3.5 μm） using a mobile phase consisting of 0.1% formic acid in aqueous solution （containing 5 mmol/L ammonium acetate） and 0.1% formic acid in methanol. Detection was carried out using electrospray ionization in positive mode with full ion MS/MS （All Ions MS/MS） scanning. Quantitation was achieved using a matrix-matched external calibration method. The results showed that this method can effectively reduce matrix effects， and 183 compounds exhibited good linearity within their respective ranges， with linear correlation coefficients （<i>R</i>²） greater than 0.995. The screening detection limits （SDLs） and limits of quantification （LOQs） for 172 pesticides in goji berries ranged from 1 to 50 μg/kg and 5 to 50 μg/kg， respectively. For mulberries， the SDLs and LOQs ranged from 1 to 20 μg/kg and 5 to 20 μg/kg， respectively. Additionally， the SDLs for 11 mycotoxins in goji berries were between 1 and 20 μg/kg， with corresponding LOQs of 5 to 50 μg/kg. In mulberries， the SDLs ranged from 1 to 10 μg/kg， while the LOQs were between 5 and 20 μg/kg. Overall， the LOQs of 183 compounds in mulberries were less than 20 μg/kg， and the proportions of pesticides and mycotoxins with LOQs less than 20 μg/kg in goji berries were 98.3% and 81.8%， respectively. At the spiked levels of 1， 2， and 10 times LOQs， the recoveries of 183 compounds ranged from 70.0% to 118.5%， 70.6% to 118.8%， and 71.2% to 119.0%， respectively， with relative standard deviations （RSDs） all less than 20.0%. The intra-day precision and inter-day precision of goji berries were 0.7%-9.8% and 1.0%-17.3%， respectively， whereas for mulberries were 0.8%-9.9% and 1.5%-16.0%， respectively. This method was applied to detect pesticides and mycotoxins in 15 batches of goji berries and 10 batches of mulberries， and a total of 16 compounds （including 13 pesticides and 3 mycotoxins） were detected with contents ranging from 5.61 to 622.47 μg/kg. Both detection rate and average content of pesticides and mycotoxins in goji berries were higher than those in mulberries. In addition， a preliminary risk assessment was conducted on the neonicotinoid pesticides with high detection rates （acetamiprid and imidacloprid）. The results showed that the chronic dietary intake risk values （%ADI） of acetamiprid and imidacloprid in goji berries were 0.04% and 0.02%， respectively. Both values are below 100% of the ADI in goji berries and are within acceptable limits. To ensure the safety and quality of goji berry and mulberry products， it is necessary to enhance the management and storage condition control of pesticides and mycotoxins. The results indicated that this method is simple to operate， highly sensitive， and suitable for high-throughput qualitative screening and accurate quantification of multiple pesticide residues and mycotoxins in both goji berries and mulberries. This method can provide reference for high-throughput screening of pesticide residues and mycotoxins in other berry medicinal and edible substances. Furthermore， it can indirectly promote industrial upgrading， facilitate the internationalization of medicinal and edible substances， and achieve a win-win situation regarding health value and economic benefits through technological innovation and the enhancement of standards.