高效液相色谱-四级杆/静电场轨道肼高分辨率质谱检测蜂蜜中的4-甲基咪唑和2-甲基咪唑

Direct determination of 4-methylimidazole and 2-methylimidazole in honey by high performance liquid chromatography - quadrurpole/electrostatic field orbitrap high resolution mass spectrometry

中文关键词:  高分辨率质谱  蜂蜜  焦糖色素  4-甲基咪唑  2-甲基咪唑

英文关键词:high resolution mass spectrometry (HRMS)  honey  caramel colours  4-methylimidazole  2-methylimidazole

中文摘要:

      目的 建立高效液相色谱-四级杆/静电场轨道肼高分辨率质谱法直接测定蜂蜜中4-甲基咪唑和2-甲基咪唑的方法。方法 用水溶解蜂蜜样品, 经0.22 μm粒径的微孔膜过滤后, 采用Agilent HILIC Plus(2.1 mm × 100 mm, 3.5 μm)色谱柱进行分离, 以体积比为8:2的乙腈与5 mmol/L乙酸铵水溶液为流动相进行等度洗脱。质谱采用正离子模式, 在质荷比(m/z)50~400范围内通过高分辨质谱全扫描模式提取目标化合物的精确质量数。结果 在本文建立的色谱条件下, 4-甲基咪唑(4-MI)和2-甲基咪唑(2-MI)能够得到较好的分离, 高分辨率质谱提取的质量准确度小于5×10-6(5 ppm)。该方法对4-MI的检测限可达50 μg/kg, 对2-MI的检测限可达25 μg/kg。两种待测物质采用外标法定量, 线性良好, 相关系数均大于0.99。通过加标验证, 在50、100和150 μg/kg 三个加标水平下, 蜂蜜中4-MI和2-MI的平均回收率为73.2 %~107.9 %, 相对标准偏差(RSD)小于9.7 %。结论 该方法样品处理过程简单, 不使用有机溶剂, 灵敏度高, 适用于任何蜜种的测定, 可以作为蜂蜜中是否掺入焦糖色素的检测方法。利用该方法对国内外各地区12个蜜种的30个蜂蜜样品进行检测, 均未检出4-MI和2-MI。

英文摘要:

      Objective A method of high performance liquid chromatography- quadrurpole/ electrostatic field orbitrap high resolution mass spectrometry (HPLC-Q/qrbitrap MS) was developed to determine 4-methylimidazole and 2-methylimidazole in honey. Methods The honey samples were diluted with deionized water, and then filtered by a polytetrafluoroethylene (PTFE) membrane with pore size of 0.22 μm. The analytes were separated on an Agilent HILIC Plus (2.1 mm × 100 mm, 3.5 μm) column through isocratic elution with acetonitrile and 5 mmol/L of ammonium acetate aqueous solution (v:v, 8:2). Full scan experiments were performed over the range of m/z 50~400 in positive mode to extract the accurate mass of analytes. Results Under the optimal condition, 4-methylimidazole (4-MI) and 2-methylimidazole (2-MI) were well separated, and the accuracy of extracted mass routinely detected was below 5×10-6. The detection limits for 4-MI and 2-MI were 50 μg/kg and 25 μg/kg, respectively. Good linearities were provided in their respective linear ranges with correlation coefficients higher than 0.99. The average recoveries at three spiked levels (50, 100 and 150 μg/kg) were in the range of 73.2 %~107.9 % and the relative standard deviations (RSDs) lower than 9.7 %. Conclusion The proposed method was simple, on use of organic solvents, sensitive, and can therefore meet the requirements of the determination of caramel color in all kinds of honey. The method was applied to 30 honey samples of 12 species from domestic and other countries. The results showed that neither 4-MI nor 2-MI was detected.