A rapid precolumn derivatization combined with high performance liquid chromatography (HPLC) with fluorescence detection method for the determination of the 1-deoxynojirimycin (DNJ) content in functional milk powder. Samples were extracted with 60% methanol in water. In pH 8.5 borate buffer solution, o-phthalaldehyde was added as a derivatizing agent to remove the interference from primary amines. DNJ in samples reacted with 9-fluorenylmethoxycarbonyl chloride to form a complex with fluorescence absorption. The separation was performed on a C₁₈ column (150 mm × 4.6 mm, 2.7 μm). Mobile phase A was 10 mmol/L sodium acetate buffer solution, and mobile phase B was acetonitrile. Gradient elution was performed at a flow rate of 1.5 mL/min. The column temperature was 45 ℃. The excitation wavelength was 275 nm. The emission wavelength was 320 nm. Good separation of DNJ from other components was achieved. The detection limit was 4 ng/mL, and the calibration curve was linear in the range of 0.01 to 50 μg/mL, with a determination coefficient (R²) > 0.999. The recovery rates ranged from 101.8% to 104.1%. The method was validated to be stable and reliable, and could be used as an effective method for determining the content of DNJ in milk powder.

In this study, we established a method for the determination of three metabolic regulators including clomiphene, trimetazidine and meldonium in foods by pass-through solid phase extraction combined with ultra-high performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS). The samples were extracted with 5% formic acid in acetonitrile, and the extract was purified on a pass-through solid phase extraction column and chromatographically separated on an Amide column (3.0 mm × 100 mm, 1.7 μm). The separated analytes were detected in the multiple reaction monitoring (MRM) mode, and quantitated by an internal standard method. Good linearity was observed for clomiphene and trimetazidine within the concentration range of 1.0-40.0 ng/mL, and 5.0-200.0 ng/mL for meldonium. The average recoveries for spiked samples ranged from 81.3% to 100.7%, and the relative standard deviations (RSD) were between 0.3% and 6.1% (n = 6). The developed method was simple, rapid and practical with low matrix interferences, and was generally suitable for the determination of clomiphene, trimetazidine and meldonium in foods, which could provide effective technical support for the assurance of food safety for sports events.