A QuEChERS-LC-Q-TOF/MS analysis method for the detection of 255 pesticides in Radix Codonopsis and Angelica sinensis decoctions was established. The transfer behaviours of 22 frequently detected pesticides were analysed.

Background: Even though the use of β-agonists in livestock has been banned in many countries, β-agonists abuse is still out of control owing to time-consuming and complicated determination techniques. Objective: This study applied ambient thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS) as a new strategy for rapidly screening seven β-agonists. As it does not require pretreatment, this method allows on-site and real-time detection. Method: Samples were collected directly using a simple metal probe. Analytes on the probe were desorbed and ionized by TD-ESI, after which analyte ions were detected using a triple quadrupole mass analyser. Results: The results showed that a thermal desorption temperature of 320°C and nebulizer pressure of 3 psi demonstrated the highest sensitivity. Excellent linear relationships were obtained in concentrations ranging from 10 to 400 μg/kg. The limit of detection of the method was 1–10 μg/kg with RSDs of 7.2–14.6%. A positive sample was verified using HPLC coupled with triple quadrupole tandem mass spectrometry, consistent with the results from TD-ESI/MS. Conclusion: This method was the first to apply TD-ESI/MS to rapid analyse β-agonists in livestock hair and was proven to be accurate, fast, and environmentally friendly. Because qualitative screening for each analysis was completed within approximately 1 min, the method could contribute to preventing non-compliance in the flow of animal-derived food to the market. Highlights: This method was a promising method for the rapid screening of β-agonists in livestock hair at any time of breeding without imposing any harm to animal which proven to be a rapid, in situ, and non-destructive detection technique without any pretreatment.

Based on liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS), a high-throughput method was developed and validated for the simultaneous detection of 270 pesticides and two quality markers (Q-markers)—ferulic acid and ligustilide—in Angelica sinensis (AS) decoction. Among 50 batches of commercial samples, 15 pesticides were detected. This study dynamically monitored the effects of processing on the content of these 15 pesticides and the two Q-markers. The results showed that distinct differences were observed in the transfer behaviors of the pesticides and Q-Markers during soaking and the first and secondary boiling stages. The decoction transfer rates were calculated and incorporated to establish a risk assessment model applicable to AS. During the decoction, density functional theory (DFT) analysis, combined with LC-Q-TOF/MS confirmation, was employed to elucidate the thermal degradation mechanism of chlorpyrifos. DFT-based thermodynamic analysis was used to explain the significant differences in thermal loss between ferulic acid and ligustilide.

Rationale: Pesticide isomers are widely available in agricultural production and may vary widely in biological activity, potency, and toxicity. Chromatographic and mass spectrometric analysis of pesticide isomers is challenging due to structural similarities. Methods: Based on liquid chromatography-time of flight mass spectrometry (LC-Q-TOF/MS), identification of cis-trans isomeric pesticides was achieved through retention time, characteristic fragment ions, and relative abundance ratio. The cleavage pathways of six cis-trans isomers were elucidated through collision-induced dissociation (CID) to explain the origins of different fragment ions. The energy-resolved mass spectrometry combined with computational chemical density functional theory in terms of kinetics, thermodynamics, and bond lengths, the specific process of fragments were simulated to explain the reasons for the differences in characteristic fragment ions and abundance ratios. Results: Based on the above study, a high-resolution mass spectrometry method was developed for the separation and analysis of cis-trans isomers of pesticides in traditional Chinese medicine Radix Codonopsis , and six pesticide isomers were distinguished by retention time, product ions, and relative abundance ratios. The limits of quantification of the six pesticides were up to 10 μg/kg, and the linear ranges of them were 10-200 μg/kg, with the coefficients of determination (R ² )＞0.99, which demonstrated the good linearity of the six pesticides. The recoveries of the pesticides at the spiked concentrations of 10 μg/kg, 20 μg/kg, and 100 μg/kg reached 70-120% with the RSDs ≤20%. Conclusions: It was demonstrated that the application of the method was well-suited for accurate qualitative and quantitative analysis for each isomers with different structures which could avoid false negative results caused by ignoring another isomers effectively.