Develop an external standard method for high-flux determination of veterinary drug residues liquid milk without solid phase extraction.

To get rid of the singularity of the detection of veterinary drug residues in liquid milk, a high-throughput determination was developed for 126 VDRs in 17 categories in liquid milk based on the one-step extraction coupled with LC-HRMS (UPLC-Q-Exactive-Orbitrap-MS). The results showed that adding 2.5 mL of 0.1 mol/L Na2EDTA-McIlvaine in acetonitrile-methanol extractant (50:50, V/V) could effectively improve the response intensity of veterinary drug residues in liquid milk, reduce the matrix effect and eliminate the need for expensive SPE purification. The established external standard quantitative method has a LOD of 0.01-0.30 μg/L for all categories of veterinary drug residues, good linearity in the concentration range of LOQ of 0.03-1.00 μg/L, and correlation coefficients (r) were all greater than 0.995. The spike recoveries at all three levels were between 80.30% and 119.95%. The positive detection rate of this method in 128 actual samples was 8.59%.