Characterization of the Internal Energy of Ions Produced by Electrospray Ionization Using Substituted Benzyl Ammonium Thermometer Ions
Characterization of the Internal Energy of Ions Produced by Electrospray Ionization Using Substituted Benzyl Ammonium Thermometer Ions
复制标题
使用取代的苄基铵温度计离子对电喷雾电离产生的离子的内能进行表征
DOI：
10.1021/jasms.2c00116
复制
发表时间：
2022
影响因子：
3.2
通讯作者：
Saikusa Kazumi
中科院分区：
文献类型：
--
作者：
Asakawa Daiki;Saikusa Kazumi
我们建议使用取代的苄基铵物种作为温度计离子的电喷雾电离（ESI）产生的离子的内部能量分布的特征。重要的是，我们发现苄基铵物质的活化优先通过N-Cα键断裂提供苄基阳离子。此外，在CCSD（T）/cc-PVTZ//M06-2X-D3/6-311++G（d，p）水平上的计算表明，所测试的模型离子的碎裂阈值能量在86 ~ 192 kJ mol-1之间，明显低于传统的4-取代苄基吡啶温度计离子的碎裂阈值能量.因此，取代的苄基铵适合于在典型实验条件下表征ESI过程。此外，发现离子的内能取决于离子漏斗的射频电压，其用于增加离子从大气到真空条件的传输效率。我们报告的方法将有助于确定最佳的离子漏斗射频电压的小分子，如代谢物的分析。此外，苄基铵是市售的，这将有助于常规和广泛的测量离子的内部能量分布。
We propose the use of substituted benzyl ammonium species as thermometer ions to characterize the internal energy distribution of the ions produced by electrospray ionization (ESI). Crucially, we found that the activation of the benzyl ammonium species preferentially provided a benzyl cation via N–Cα bond cleavage. In addition, calculations at the CCSD(T)/cc-PVTZ//M06-2X-D3/6-311++G(d,p) level of theory revealed that the threshold energies of fragmentation of the tested model ions ranged from 86 to 192 kJ mol–1, significantly lower than those of conventional 4-substituted benzylpyridinium thermometer ions. Thus, the substituted benzyl ammoniums are suitable for the characterization of the ESI process under typical experimental conditions. Further, the internal energies of the ions were found to depend on the radiofrequency voltage of the ion funnel, which is used to increase the transport efficiency of the ions from atmospheric to vacuum conditions. Our reported method will aid the determination of the optimum ion-funnel radiofrequency voltage for the analysis of small molecules such as metabolites. Furthermore, benzyl ammoniums are commercially available, which will facilitate the routine and widespread measurement of the internal energy distributions of ions.