Abstract: A method for determining urea in milk and milk powder was developed using high performance liquid chromatography with fluorescence detection (HPLC-FLD). Samples were extracted with a mixture of water and ethanol, the supernatant was derivatized with a solution of xanthydrol in acidic condition. The chromatographic separation was performed on a reversed-phase C18 column using a mobile phase consisting of acetonitrile and sodium acetate solution. The derivatized products were separated and tested using a fluorescence detector at λex 213 nm and λem 308 nm. The method showed a good linear relationship in the range of 0.1–10.0 μg/mL, with R2 > 0.999. The spiked recoveries of urea in formula milk powder and liquid milk samples were in the range of 104%–106% and 83.4%–101% with RSD 2.1% –5.7% and 3.2%–4.9%, respectively. The limits of detection (LODs) in formula milk powder and liquid milk were 30 and 12 mg/kg, respectively. This method proved rapid, sensitive, reliable and reproducible.

Key words: urea; milk; milk powder; high performance liquid chromatography-fluorescence detection; xanthydrol

摘要： 建立了高效液相色谱-荧光检测器法测定乳及乳粉中尿素的方法.样品经乙醇水溶液提取后,在酸性条件下与9-羟基呫吨衍生反应,以乙腈和乙酸钠溶液做流动相,C18反相色谱柱分离,荧光检测器λex为213 nm和λem为308 nm测定,外标法定量.结果表明:在0.1～10.0 μg/mL范围内线性良好,R2＞ 0.999,配方奶粉和液态奶中加标回收率分别为104％～106％和83.4％～101％,RSD分别为2.1％～5.7％和3.2％～4.9％.在乳粉和液态奶中方法检出限分别为30 mg/kg和12 mg/kg.该方法简便、快速,灵敏度高,结果准确可靠,检验数据重现性好.

关键词: 尿素；乳；乳粉；高效液相色谱-荧光检测法；9-羟基呫吨