本文使用2,4-二硝基苯肼衍生法使白菜中甲醛生成甲醛-2,4-二硝基苯腙，再使用乙腈提取富集甲醛-2,4-二硝基苯腙（衍生物），后经液相色谱串联质谱对其浓度进行检测。结果显示，该法中甲醛的检出限为3.06μg/Kg，当白菜中甲醛添加含量在1-18mg/Kg时，甲醛线性良好（r2=0.994）。对白菜中三种浓度（0.5、1、5 mg/Kg）甲醛添加进行6平行回收实验结果表明，三种浓度平行添加回收率在102-105%之间，相对标准偏差为3-8%之间，回收稳定，精密度良好。

Formaldehyde in Chinese cabbage was derivated with 2,4-dinitrophenylhydrazine, extracted by acetonitrile and tested by liquid chromatography tandem mass spectrometry. Results showed that the detection limit of formaldehyde in this method was 3.06μg/Kg. When the spiking amout in Chinese cabbage was 1-18mg / Kg, the formaldehyde amout was linearly correlated to peak area. (r2= 0.994). When the adding amount of Formaldehyde was 0.5,1,5 mg/Kg, recoveries were between 102% to 105%, and the relative standard deviations were between 3% and 8% with good stability and precision.