Determination of Nonylphenol in Milk Powder by High Performance Liquid Chromatography-Tandem Mass Spectrometry

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the determination of nonylphenol in milk powder. Samples were extracted with acetonitrile and cleaned up with a solid phase extraction column. The analytes were separated on a Waters ACQUITY UPLC BEH C₁₈ column (2.1 mm × 50 mm, 1.7 μm), detected by electrospray ionization in the multiple reaction monitoring (MRM) mode, and quantified by an external standard method. The results showed that good linearity was observed in the concentration range of 1–200 ng/mL (R² > 0.99). The limit of detection (LOD, R_S/N = 3) was 2 µg/kg and the limit of quantitation (LOQ, R_S/N = 10) was 5 µg/kg. The recoveries at different spiked levels were between 81.10% and 107.39% with relative standard deviation (RSD) ranging from 1.97% to 9.73%. This method has the advantages of accurate results, small background interference, simple operation, good stability and short pretreatment time, and is useful for the detection of nonylphenol in milk powder.