[Determination of 22 mycotoxins in milk by liquid chromatography-quadrupole/orbitrap mass spectrometry]

Mycotoxins have carcinogenic, mutagenic, hepatotoxic, nephrotoxic, immunotoxic, neurotoxic, and teratogenic properties. Thus, these substances have attracted significant attention because they pose a threat to human health. As research on mycotoxins deepens, new structural analogues of mycotoxins are constantly being discovered. In this study, a method based on high performance liquid chromatography-quadrupole/orbitrap mass spectrometry was established for the simultaneous determination of 22 mycotoxins in milk. A simple, effective, and rapid pretreatment method was optimized by focusing on the solvent type, extractant volume, and extracting salt based on the characteristics of the mycotoxins and sample matrix. The analytes were extracted using 0.5% formic acid acetonitrile solution and added with sodium chloride to separate fats from water. The samples were centrifuged at 8000 r/min (4 ℃) for 5 min using a centrifuge and then concentrated using nitrogen. The dry residue was dissolved with 50% methanol aqueous solution. Twenty-two mycotoxins were separated on a ZORBAX Eclipse Plus C₁₈ chromatographic column (100 mm×2.1 mm, 1.7 μm), and quantitative analysis was performed using the isotope internal standard method. The analytes were determined by liquid chromatography-quadrupole/orbitrap mass spectrometry in positive electrospray ionization mode. Qualitative analyses of the compounds were performed in full mass spectrometry/data-dependent tandem mass spectrometry (MS/dd-MS²) mode. Good linearities in the range of 0.5-100.0 μg/L were observed for the 22 mycotoxins, and the correlation coefficients (R²) were greater than 0.999. The limits of detection (S/N=3) and quantification (S/N=10) ranged from 0.3 to 0.5 μg/kg and from 1.0 to 1.5 μg/kg, respectively. The average recoveries of the 22 mycotoxins at three spiked levels of 1.5, 5.0, and 15 μg/kg were between 84.7% and 100.8%, with relative standard deviations (RSDs) of 1.2%-9.9%. These findings indicate that the method has high sensitivity and accuracy as well as good precision. Finally, the method was applied to the detection and analysis of mycotoxins in 25 actual commercial milk samples. The results revealed that the selected samples were not contaminated with any of the mycotoxins analyzed. Thus, the proposed method is useful as a quick preprocessing and confirmatory method for the simultaneous determination of mycotoxins in milk.