A gradient clean-up method for the quantification of five kinds of banned drugs (two hormones, two sedatives, and one chloramphenicol) in milk powder was developed. We used the combination of solid-phase extraction purification with gas chromatography and mass spectrometry. Milk powder was initially hydrolyzed by β-glucuronidase/arylsulfatase, and then the hydrolyzed solution was concentrated and purified using a C8 and cation resin solid-phase extraction column. To isolate hormones and chloramphenicol drugs, products from the previous step were diluted with methanol and further purified using a silica and diatomite solid-phase extraction column. After derivatization, the drugs were analyzed by gas chromatography with mass spectrometry, and the hydrolyzed solution was diluted with 5% ammoniated methanol to purify sedatives before gas chromatography with mass spectrometry analysis. Results showed that after adding the banned drugs at concentrations of 0.3-10.0 μg/kg, the average recovery range was 78.2-97.3% with relative standard deviations of 5.3-12.5%. The limit of quantification of the banned drugs (S/N ≥ 10) was 0.3-5.0 μg/kg, whereas the limit of detection (S/N ≥ 3) was 0.1-2.0 μg/kg. The solid-phase extraction gradient purification system was simple, rapid, and accurate, and could satisfy the detection requirements of hormone, sedatives, and chloramphenicol drugs when used together with gas chromatography and mass spectrometry.
Keywords: Banned drugs; Gas chromatography with mass spectrometry; Gradient purification; Milk powder.
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