A new method for rapid screening for and identification of 11 foodborne stimulants and five alkaloids in hot pot soup base seasoning by ultra-high performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF/MS) was developed. The analytes from samples were extracted with 80% aqueous acetonitrile, cleaned up on a PRiME HLB column, and separated on a Kinetex F5 column prior to qualitative screening and quantitative analysis in the high-resolution scanning mode using multiple reaction monitoring (MRM). The relative deviations of the exact mass numbers of the 16 compounds were less than 5.0 × 10^-6, and the linearity of the calibration curves was good with correlation coefficient (R²) greater than 0.9970. The recoveries of the analytes were 75.2%–105.4%, with relative standard deviation (RSD) of 1.3%–7.4% (n = 6). The limit of detection (LOD) was 0.05–1.0 µg/kg, and the limit of quantitation (LOQ) was 0.10–2.0 µg/kg. The developed method is simple, rapid, accurate, and practical.

A method for the determination of 25 β-receptor agonist residues in milk and dairy products was established based on ultra-high performance liquid chromatography-tandem mass spectrometry. Samples were enzymatically hydrolyzed in 0.2 mol/L ammonium acetate solution at pH 5.2 for 16 h. After the removal of fat and protein through glass fiber filter paper, the filtrate was purified by solid phase extraction (SPE) using a PRiME MCX solid phase extraction column, and separated on a Waters BEH C₁₈ column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase composed of acetonitrile and 0.1% formic acid in water. Mass spectrometry was performed using an electrospray ionization source (ESI) in the positive ion mode with multiple reaction monitoring (MRM), and quantitative determination was performed using the internal standard method. The proposed method showed good linearity for all analytes in the concentration range of 0.2–50.0 ng/mL with coefficients of determination (R²) greater than 0.996; the recoveries ranged from 80.3% to 106.2% with relative standard deviations (RSDs) of 0.6%–8.5% (n = 6). The limits of detection (LOD) were 0.05–0.10 μg/kg, and the limits of quantification (LOQ) were 0.10–0.20 μg/kg. This method is simple, efficient and suitable for the determination of the 25 β-receptor agonist residues in milk and dairy products.