Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602-5700, United States.
Anal Chem. 2012 Jun 5;84(11):4851-7. doi: 10.1021/ac300379a. Epub 2012 May 7.
We demonstrate a technique for determining molecular collision cross sections via measuring the variation of Fourier transform ion cyclotron resonance (FTICR) line width with background damping gas pressure, under conditions where the length of the FTICR transient is pressure limited. Key features of our method include monoisotopic isolation of ions, the pulsed introduction of damping gas to a constant pressure using a pulsed leak valve, short excitation events to minimize collisions during the excitation, and proper choice of damping gas (Xe is superior to He). The measurements are reproducible within a few percent, which is sufficient for distinguishing between many structural possibilities and is comparable to the uncertainty in cross sections calculated from computed molecular structures. These techniques complement drift ion mobility measurements obtained on dedicated instruments. They do not require a specialized instrument, but should be easily performed on any FTICR mass spectrometer equipped with a pulsed leak valve.
我们展示了一种通过测量傅里叶变换离子回旋共振（FTICR）线宽随背景阻尼气体压力的变化来确定分子碰撞截面的技术，在这种情况下，FTICR 瞬变的长度受到压力限制。我们方法的关键特点包括离子的单同位素隔离、使用脉冲泄漏阀以恒定压力脉冲引入阻尼气体、短激发事件以最小化激发过程中的碰撞以及适当选择阻尼气体（Xe 优于 He）。测量结果的重现性在百分之几以内，足以区分许多结构可能性，与从计算分子结构计算得出的截面不确定性相当。这些技术补充了专门仪器上获得的漂移离子迁移率测量。它们不需要专门的仪器，但应该可以在任何配备脉冲泄漏阀的 FTICR 质谱仪上轻松进行。
