建立了高效液相色谱仪（HPLC）与电感耦合等离子质谱仪（ICP-MS）联用同时测定乳制品中的三价铬和六价铬的方法。样品在EDTA缓冲液中煮沸，冷却后在离心机中以8000 r/min离心10 min沉降蛋白质，取清液用0.45 μm滤膜过滤，就完成了三价铬和六价铬的同时提取。以NH4NO3为流动相（pH=7.0~7.2），流速为0.6 mL/min，使用HPLC-ICP-MS仅需4 min就完成了提取液中三价铬和六价铬的分离和测定。本文着重分析了各种前处理条件对测定结果的影响。EDTA加入量要过量以消除钙、镁等元素的影响；煮沸能显著加快EDTA与三价铬的络合速度，但时间不能过长，以2~3 min为宜；pH值在7.0~7.2时两种形态的铬回收率高，分离效果好。实验表明，三价铬和六价铬的线性范围在0.2~20 μg/L，相关系数均大于0.9995，检出限分别为0.034 μg/L和0.066 μg/L。本方法操作简单，灵敏度高，准确性和精密度好。

A method was developed for the simultaneous determination of chromium(Ⅲ) and chromium(Ⅵ) in dairy products by high performance liquid chromatography(HPLC) coupled with inductively coupled plasma-mass spectrometry(ICP-MS). The sample was boiled in EDTA buffer solution, cooled down and centrifuged at 8000 r/min for 10 min to separate the protein. Then the supernatant was filtrated through 0.45 μm filter membrane, and chromium(Ⅲ) and chromium(Ⅵ) were simultaneously extracted. Using NH4NO3 as mobile phase (pH=7.0~7.2), Chromium(Ⅲ) and chromium(Ⅵ) were separated and detected in 4 min by HPLC-ICP-MS at a flow rate of 0.6 mL/min. The effects of various pretreatment conditions on test results were researched. The amount of EDTA should be excessive to eliminate the influence of calcium, magnesium and other elements. The complexation rate of EDTA with Chromium(Ⅲ) was significantly increased by boiling, but the time should not be too long, and 2~3 min was appropriate. The two chromium species had good recoveries and separation effect under pH 7.0~7.2. The results showed that the linear ranges for Chromium(Ⅲ) and chromium(Ⅵ) were between 0.2 and 20 μg/L with linear coefficients more than 0.9995, and the detection limits were 0.034 and 0.066 μg/L. The method had a simple pretreatment procedure, high sensitivity and good accuracy and precision.

广东省质量技术监督局科技项目资助（2011CS09）