奶粉中三聚氰胺HPLC-IC分析方法的比对

采用反相离子对色谱法、亲水相互作用色谱法及阳离子交换色谱法测定奶粉中三聚氰胺的含量。奶粉样品前处理采用水- 乙酸提取后过RP柱和甲酸提取后乙腈沉淀两种方法，反相离子对色谱法采用C18 柱和10mmol/L庚烷磺酸钠与10mmol/L 柠檬酸的缓冲溶液- 乙腈(85:15，V/V)的流动相；亲水相互作用色谱法采用HILIC 柱和20mmol/L甲酸胺- 乙腈(10:90，V/V)的流动相；阳离子交换色谱法采用IonPac CS17 阳离子交换柱和6mmol/L 硫酸的流动相。流速1.0mL/min，检测波长240nm。结果表明，3 种方法测定三聚氰胺在0.1～25.0mg/L 范围内线性均很好(r=1.0000)，样品加标回收率在93.91%～99.96% 范围内。3 种方法中，反相离子对色谱法对三聚氰胺的响应值最高，阳离子交换色谱法则能用最短的时间检测出三聚氰胺，而亲水相互作用色谱法在假阳性的判断上可作为其他两种方法的补充。

Comparison of Three Chromatographic Methods for the Determination of Melamine in Powdered Milk

Three chromatographic methods, i.e., reversed-phase ion pair chromatography, hydrophilic interaction chromatography and cation exchange chromatography, were established to determine melamine in powered milk. Before hydrophilic interaction chromatographic analysis, samples were extracted with formic acid, precipitated with acetonitrile for the removal of proteins and centrifugated. While for other two methods, the sample pretreatment was based on extraction with aqueous acetic acid solution, precipitation, centrifugation and cleanup on a RP column. The chromatographic separation was performed on a C18 column using a mobile phase composed of a buffer solution containing 10 mmol/L sodium heptanesulfonate and 10 mmolL citric acid and acetonitrile (85:15, V/V) in reversed-phase ion pair chromatographic analysis. A HILIC column and 20 mmol/L ammonium formate/acetonitrile (10:90, V/V) as mobile phase were used for hydrophilic interaction chromatographic analysis. The column and mobile phase employed for cation exchange chromatographic analysis melamine were CS17 column and 6 mmol/L of sulfuric acid. A mobile phase flow rate of 1.0 mL/min was employ for all three chromatographic methods and the detection wavelength was set at 240 nm. The results showed that the calibration curves of melamine derived from the methods were all linear within the range from 0.1 to 25.0 mg/L (r = 1.0000). The recoveries for melamine determined by reversed-phase ion pair chromatography, hydrophilic interaction chromatography and cation exchange chromatography were 95.75%, 99.96% and 93.91%, respectively. Reversed-phase ion pair chromatography had the highest response to melamine, cation exchange chromatography could detect melamine within the shortest time and while hydrophilic interaction chromatography could be used as a supplementary method for the determination of false positive samples.