三聚氰胺毒牛奶事件对中国乳制品行业造成了巨大冲击。 为保证食品安全, 贯彻国家相关管理规定, 在乳制品收购环节开展液态乳中三聚氰胺快速检测具有重要的现实意义。 研究通过絮凝过滤进行液态乳中三聚氰胺快速分离的前处理方法, 样品使用碱式氯化铝(PAC)絮凝后经水性滤膜过滤, 即可有效去除液态乳中的脂肪等非水溶性干扰物, 得到澄清滤液用于后续检测。 通过实验确定碱式氯化铝的添加质量比例为2%～3%时有较高的过滤效率; 当混合液为弱碱性条件下具有较好的絮凝效果。 采用高效液相色谱方法实验测得样品回收率在90%以上, 并估算了回收率的置信区间。 采用本方法前处理所得样品与离心前处理方法相比更澄清, 采用增敏拉曼方法获得的光谱曲线基线更平整, 除杂质效果更好。 该前处理方法通用性好, 分离效果好, 比现有三聚氰胺检测标准方法前处理过程更简单、 快速, 如用于现有快速液相法和拉曼光谱法中前处理步骤将使检测效率大大提高。

The present paper proposed for the first time the flocculation-filtration method for separation of interfering substances in milk, such as fat. In this method only two steps were carried out. Firstly, aluminum chloride (PAC, Al2(OH)nCl6-n) is used to flocculate the milk; Secondly, water filter was used to filter the mixture. Then the clear filtrate could be used for the detection of melamine. The whole preprocessing would not take more than one minute. The pretreatment process was optimized. Experiments show that the adding proportion of PAC should be about 2%～3% for best filtration efficiency, and that it would have the best flocculation effect when the mixture was mildly alkaline. High performance liquid chromatography experiments show that the melamine recovery of this method is more than 90%. Samples pretreated by the flocculation-filtration method were clearer and the baselines of spectral curve obtained by sensitizing Raman method were more smooth which means better purification compared to those samples pretreated by centrifugal pretreatment method. The pretreatment method proposed can be used in HPLC and Raman spectroscopy methods for rapid detecting melamine in liquid milk. This method shows better separation effect, simpler operation, and lower time and money cost than those pretreatment processes in the existing standard melamine detection method for milk. By use of this pretreatment method, the melamine rapid detection efficiency would be greatly improved.