牛奶中矿物元素和稳定同位素比的测定及在产地分析中的应用

Determination of Multi-elements and Stable Isotope Ratios in Milk and Discrimination Their Geographical Origin

摘要:

本文应用电感耦合等离子质谱仪（ICP-MS），同位素比质谱仪（IRMS）对牛奶中Li、Na等40种元素含量和碳、氮、氢、氧稳定同位素比值进行测定，并应用于牛奶产地分析中。牛奶样品经冷冻干燥成粉末后，通过ICP-MS对元素含量进行测定，EA-IRMS测定氮稳定同位素比值（δ15N），通过EA-IRMS直接测定牛奶中碳稳定同位素比值（δ13C），GasBench-IRMS测定牛奶水中的氢和氧稳定同位素比值（δ2H和δ18O）。应用上述方法对德国、西班牙、意大利、澳大利亚、新西兰、中国和奥地利的牛奶样品进行检测，并对测定结果进行多元统计分析（方差分析、主成分分析、聚类分析和判别分析），对牛奶产地的归属进行研究。研究结果表明，有10种元素（As、Se、Rb、Sr、Mo、Cd、Cs、Ba、Tl、Bi）和4种稳定同位素比（δ13C、δ15N、δ2H、δ18O）在不同国家和地区的牛奶中存在显著性差异（p<0.05），德国和意大利，中国，奥地利，澳大利亚和新西兰的牛奶可进行一定的聚类区分，应用As、Se、Rb、Sr、Mo、Cs、Ba、Tl、δ13C、δ15N和δ2H指标的组合分析，对7个国家牛奶产地的整体判别准确率为92.4%。

Abstract:

In this paper, the inductively coupled plasma mass spectrometry (ICP-MS) was used for the determination of Li, Na and other 38 elements, the elemental analysis-isotope ratio mass spectrometry (EA-IRMS) and GasBench-IRMS were used for the determination of the stable isotope ratios of carbon, nitrogen, hydrogen and oxygen in milk, and for the feasibility assessment of milk geographical origin in different country. The milk sample was freeze-dried into a powder, and then determined by EA-IRMS or ICP-MS to obtain stable isotope ratios of nitrogen (δ15N) and mineral elements. The milk sample was detected by EA-IRMS or GasBench-IRMS to obtain stable isotope ratios of carbon, hydrogen and oxygen (δ13C, δ2H and δ18O). The milk samples were collected from Germany, Spain, Italy, Australia, New Zealand, China and Austria, and then the stable isotope ratios of carbon, nitrogen, hydrogen, oxygen and multi-elements were detected. The values of δ13C, δ15N, δ2H, δ18O and multi-elements were distinguished by multivariate statistical analysis (including ANOVA, Duncan’s multiple comparison,correlation analysis, principal component analysis, cluster analysis and discriminant analysis) using the SPSS software package for windows. The results showed that the As、Se、Rb、Sr、Mo、Cd、Cs、Ba、Tl、Bi、δ13C、δ15N、δ2H and δ18O were significantly different (p< 0.05)，different clusters were observed in Germany and Italy, China, Austria Australia and New Zealand, and the accuracy of discrimination for milk geographical origin was 92.4% by the combined indicators of As, Se, Rb, Sr, Mo, Cs, Ba, Tl, δ13C, δ15N and δ2H.