Perry Richard H, Hu Qizhi, Salazar Gary A, Cooks R Graham, Noll Robert J
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
J Am Soc Mass Spectrom. 2009 Aug;20(8):1397-404. doi: 10.1016/j.jasms.2009.02.011. Epub 2009 Feb 12.
A method is described to improve resolution and peak shape in the Orbitrap under certain experimental conditions. In these experiments, an asymmetric anharmonic axial potential was first produced in the Orbitrap by detuning the voltage on the compensator electrode, which results in broad and multiply split mass spectral peaks. An AC waveform applied to the outer electrode, 180 degrees out of phase with ion axial motion and resonant with the frequency of ion axial motion, caused ions of a given m/z to be de-excited to the equator (z = 0) and then immediately re-excited. This process, termed "rephasing," leaves the ion packet with a narrower axial spatial extent and frequency distribution. For example, when the Orbitrap axial potential is thus anharmonically de-tuned, a resolution of 124,000 to 171,000 is obtained, a 2- to 3-fold improvement over the resolution of 40,000 to 60,000 without rephasing, at 10 ng/microL reserpine concentration. Such a rephasing capability may ultimately prove useful in implementing tandem mass spectrometry (MS/MS) in the Orbitrap, bringing the Orbitrap's high mass accuracy and resolution to bear on both the precursor and product ions in the same MS/MS scan and making available the collision energy regime of the Orbitrap, approximately 1500 eV.
本文描述了一种在特定实验条件下提高轨道阱分辨率和峰形的方法。在这些实验中，首先通过使补偿电极上的电压失谐在轨道阱中产生不对称非谐轴向势，这会导致质谱峰变宽并出现多重分裂。施加到外部电极的交流波形与离子轴向运动相位相差180度且与离子轴向运动频率共振，使给定质荷比（m/z）的离子去激发到赤道面（z = 0），然后立即重新激发。这个过程称为“重新定相”，使离子包具有更窄的轴向空间范围和频率分布。例如，当轨道阱轴向势如此非谐失谐时，在10 ng/μL利血平浓度下，可获得124,000至171,000的分辨率，相较于未进行重新定相时40,000至60,000的分辨率提高了2至3倍。这种重新定相能力最终可能被证明在轨道阱中实施串联质谱（MS/MS）时很有用，使轨道阱的高质量精度和分辨率在同一次MS/MS扫描中同时作用于前体离子和产物离子，并开启轨道阱约1500 eV的碰撞能量范围。
