基于高效液相色谱-电感耦合等离子体质谱法的牛乳中铬的价态分析

采用高效液相色谱-电感耦合等离子体质谱仪测定牛乳中Cr(Ⅲ)和Cr(Ⅵ)的含量。采用PRP-X100阴离子交换柱,研究流动相浓度、流动相pH值和流速对Cr(Ⅲ)和Cr(Ⅵ)的分离度和保留时间的影响,最终选择流动相NH4NO3的浓度为0.10 mol/L、pH值为7、流速为1.0 mL/min。在优化得到的最佳实验条件下,以52Cr/53Cr自然丰度比为参考值排除了质谱和离子干扰,确定出Cr(Ⅲ)和Cr(Ⅵ)的保留时间分别为2.227 min和1.856 min;Cr(Ⅲ)和Cr(Ⅵ)线性方程的线性关系良好,且相关系数分别为0.9995和0.9997,方法检出限分别为0.015 μg/L和0.016 μg/L;样品中Cr(Ⅲ)和Cr(Ⅵ)的加标回收率在71.52%~90.27%之间。本研究确定的方法适用于牛乳中不同价态的Cr(Ⅲ)和Cr(Ⅵ)的同时测定。

Analysis of Cr Valence States in Milk by High Performance Liquid Chromatography Coupled with Inductively Coupled Plasma Mass Spectrometry

In this paper, Cr (Ⅲ) and Cr (Ⅵ) in milk were determined by high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). A PRP-X100 cation exchange column was used. The influence of mobile phase concentration, pH value and flow rate on the degree of separation and retention time was investigated. The mobile phase selected was NH4NO3solution (0.10 mol/L, pH 7) at a flow rate of 1.0 mL/min. Under the optimized conditions, the mass spectrometric and ion interferences were eliminated by using the natural abundance ratio of 52Cr to 53Cr as reference value, and the retention time of Cr (Ⅲ) and Cr (Ⅵ) were determined to be 2.227 and 1.856 min, respectively. Good linearity was observed for Cr (Ⅲ) and Cr (Ⅵ) with correlation coefficients of 0.999 5 and 0.999 7, respectively. The detection limits were 0.015 and 0.016 μg/L, respectively. The overall recoveries for the two valence states were in range of 71.52% to 90.27%. This method proved to be useful for simultaneous analysis of different Cr valence states in milk and dairy products.