元素分析-稳定同位素质谱技术在婴幼儿配方奶粉奶源地追溯中的应用

婴幼儿配方奶粉是婴幼儿的主要食品，为加强其品质监管，建立了元素分析-稳定同位素质谱（EA-IRMS）同时测定婴幼儿配方奶粉中酪蛋白δ¹⁵N和δ¹³C值的方法。通过优化的等电点沉淀法可以从婴幼儿配方奶粉中获得高纯度的蛋白（纯度大于96%）。利用纳升液相-四极杆飞行时间质谱对提取的蛋白进行定性分析，确认其为酪蛋白。利用EA IRMS测定分离得到的酪蛋白δ¹⁵N和δ¹³C值发现，δ¹⁵N 和δ¹³C与奶源产地有一定的相关性，同一产地的婴幼儿配方奶粉中酪蛋白的δ¹⁵N和δ¹³C值分布范围一致，而不同奶源产地的则存在差异。该方法前处理简单、重现性好、测试方便、准确度高，可以用来追溯国内市场上婴幼儿配方奶粉的奶源产地。

Traces of Infant Formula Milk Powders by Elemental Analysis-Stable Isotope Ratio Mass Spectrometry

In order to strengthen the supervision of the quality of infant formula milk powders which is the main food of infants，δ¹⁵N andδ¹³C of casein in infant formula milk powders were determined by elemental analysis-stable isotope ratio mass spectrometry(EA-IRMS). Casein which purity was over 96%， was extracted from milk powder by isoelectric-precipitation of proteins and identified by nano liquid chromatography & quadrupole-time-of-flight mass spectrometer(Nano LC-QTOF-MS). The ranges of δ¹⁵N and δ¹³C are correlated with the regional origins of infant formula powders. The values ofδ¹⁵N andδ¹³C of casein from the milk powders with the same origin are very similar, whereas they are quite different with different origins. It is a reliable and convenient method to determine the regional origin of infant formula powders.