浊点萃取-高效液相色谱法检测牛奶中苯甲酸

Determination of benzoic acid in milk by cloud point extraction-high performance liquid chromatography detection

建立了基于浊点萃取(CPE)测定牛奶中苯甲酸的高效液相(HPLC)色谱法。以非离子表面活性剂聚氧乙烯山梨糖醇酐单月桂酸酯(Tween-20)为萃取剂,考察了萃取剂的浓度、盐的浓度、加热温度及时间、pH值等因素对浊点萃取效果的影响。CPE方法的优化条件:Tween-20的浓度为3%(V/V)、(NH4)2SO4的浓度300g/L、在pH值为4的条件下90℃萃取10min;色谱条件:色谱柱为VenusilMPC18(4.6mm×150mm,5μm),流动相为乙酸铵水溶液(0.02mol/L)-甲醇(体积比为90:10),流速为1.0mL/min,检测波长230nm。在上述实验条件下,苯甲酸在0.2-2μg/mL时其浓度与检测信号呈线性关系,相关系数为0.9998,检出限为0.025μg/mL;在牛奶样品中加标回收率为98.90%～100.16%,相对标准偏差为1.2%～2.5%。

A method based on cloud point extraction was developed to determine benzoic acid in milk using high-performance liquid chromatography detection.The non-ionic surfactant Tween-20 was chosen as extraction solvent,the extraction parameters affecting extraction efficiency,such as concentrations of Tween-20 and（NH4）2SO4,equilibration temperature,equilibration time and pH were evaluated and optimized.The optimum CPE conditions were：3%（V/V）Tween-20,300g/L（NH4）2SO4,pH4,equilibration temperature 90℃ for 10min;chromatographic conditions were：mobile phase of ammonium acetate buffer-methanol 90：10（V/V）,flow rate 1mL/min,the detection wave length 230nm.Under the above optimized conditions,the linearity of the calibration curve for benzoic acid was in the range of 0.2～2.0μg/mL,the limits of detection was 0.025μg/mL,the correlation coefficient was 0.9998.The recovery for the standard addition of the benzoic acid in the milk ranged from 98.90% to 100.16%,the relative standard deviations was in the range of 1.2%～2.5%.