液相色谱-离子淌度-四极杆/飞行时间串联质谱法快速检测烟叶中蔗糖酯

Fast Detection of Sucrose Esters in Tobacco Leaf Using Liquid Chromatography Coupled with Ion Mobility-Quadrupole/Time of Flight Mass Spectrometry

  • 摘要: 本研究利用液相色谱-离子淌度-四极杆/飞行时间串联质谱(LC-IM-Q TOF MS)技术,建立了快速检测烟叶中蔗糖酯的定性分析方法。采用甲酸-甲醇-水混合流动相系统和正离子模式下的电喷雾离子化技术,使烟叶甲醇提取液中的蔗糖酯分子形成加钠的准分子离子,然后通过离子淌度漂移管的分离,被四极杆/飞行时间串联质谱仪检测。从烟叶中共检测出6类蔗糖四酯,它们在色谱柱上的分离相差0.2~0.8 min,在漂移管中的分离相差0.4~0.5 ms,质谱检测中的离子质量相差14 u。在此基础上,利用二级质谱解析,准分子离子的元素组成测定以及碰撞截面的测定等手段,对烟叶中6类蔗糖四酯进行结构上的定性分析。结果表明,LC-IM-Q TOF MS技术可以快速检测复杂样品中的蔗糖酯,结合多维数据定性技术能够显著提高定性分析的准确性。

     

    Abstract: Ion mobility spectrometry combined with mass spectrometry (IM-MS) has grown in popularity as a powerful analytical technique. IM is capable of separating ionized molecules in the gas phase based on their mobility in a carrier buffer gas, whereas MS is effective to measure the weight of these ions. It brings a two-dimensional correlation spectrum to obtain the relationship between the ratios of shape-to-charge from IM and the ratios of mass-to-charge (m/z) from MS. The ability to analyze a wide range of compounds makes IM-MS a valuable tool for an analytical research laboratory, which is often used to perform difficult qualitation that are not possible by other methods. Sucrose esters (SEs), as one of the major chemical compositions of tobacco leaves, are generated from one or more hydroxyl sucroses esterified with fatty acids. Research on SEs is paid more attention because of its responsibility for tobacco flavor. More than this, they are considered to be important in plant or insect interactions and possess both antibiotic and plant-growth regulating activities. Due to the complexity of esterification, the number and position of the acetyl groups in SE varies, there are a few of studies about the analysis of SEs that have been reported using GC/MS or LC/MS. But it is still difficult to characterize their structures in lack of the standard references. So it is valuable to improve the qualitative analysis of SEs in tobacco leaves. In this work, SEs in tobacco leaves were fast detected by liquid chromatography coupled with ion mobility-quadrupole/time of flight tandem mass spectrometry (LC-IM-Q TOF MS). The experiment was performed using an eluent of 0.1% formic acid in methanol-water (80∶20, V/V), and the electrospray ionization technique in positive ion mode was adopted. The sodium added quasi molecular ions of SEs from the extract of tobacco leaves were formed, separated in the ion mobility drift tube, and eventually detected by quadrupole/time-of-flight tandem mass spectrometry. As a result, six kinds of SEs were detected, with the difference of 0.2-0.8 min in LC retention time, the difference of 0.4-0.5 ms in IM drift time, and the difference of 14 u in MS ion mass. Furthermore, the SEs were identified using a multidimensional qualitative analysis approach consisting of MS/MS spectra, measurement of elemental composition for quasi molecular ion, and the calculation of CCS. In conclusion, LC-IM-Q TOF MS was proved to be one of the most efficient tools for the fast detection of SEs in complex matrices. It could improve the accuracy of qualitative analysis when coupled with the multidimensional qualitative approach.

     

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