Abstract: This paper describes a method for determination of vitamin K2 (menaquinone-7, MK-7) in milk powder using high performance liquid chromatography (HPLC). The sample was hydrolyzed with lipase (250 mg/g) for 2 h, saponified with potassium carbonate (500 mg/g), extracted with n-hexane, concentrated by rotary evaporation, reconstituted with methanol/isopropanol (4:1), and post-derivatized with C18 column and reduced column before being analyzed by HPLC with a fluorescence detector. The analyte was quantified by external standard method. The results showed that the peak of MK-7 appeared at about 19.47 min, and the calibration curve for it showed a good linear relationship in the range of 0.0–1.5 μg/mL (R2 = 0.999 95). The recoveries for blank samples spiked at 5, 10 and 25 μg/100 g were between 87.9% and 94.3%, with relative standard deviations of 0.9%–6.4%. When 2 g of sample was taken and the volume was made up to 1 mL, the detection limit was 0.15 μg/100 g and the quantification limit was 0.5 μg/100 g. The method was simple with high accuracy, sensitivity and stability, and could be used for the detection of vitamin K2 (MK-7) content in milk powder.

Key words: milk powder; vitamin K2; menaquinone-7; high performance liquid chromatography; fluorescence detector; quantitative determination

摘要： 建立使用高效液相色谱快速检测乳粉中VK2（七烯甲萘醌（menaquinone-7，MK-7））含量的方 法。乳粉样品用250 mg/g脂肪酶酶解2 h，经500 mg/g碳酸钾皂化，正己烷提取，旋转蒸发浓缩，甲醇-异丙醇 （4∶1，V/V）复溶，用C18色谱柱及还原柱柱后衍生，经高效液相色谱-荧光检测器测定，外标法定量。结果表明： MK-7在19.47 min附近出峰，标准曲线在MK-7质量浓度0.0～1.5 μg/mL范围内呈良好线性关系（R2=0.999 95）；空 白乳粉样品中MK-7添加量为5、10、25 μg/100 g时，加标回收率为87.9%～94.3%，相对标准偏差为0.9%～6.4%； 取样量为2 g、定容体积为1 mL时，MK-7检测限为0.15 μg/100 g，定量限为0.5 μg/100 g。本检测方法前处理简单， 具有较高准确度、灵敏度和稳定性，可以用于乳粉中VK2（MK-7）含量的检测。

关键词: 乳粉；VK2；七烯甲萘醌；高效液相色谱；荧光检测器；定量测定