Song Qingyu, Kothari Sameer, Senko Michael A, Schwartz Jae C, Amy Jonathan W, Stafford George C, Cooks R Graham, Ouyang Zheng
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
Anal Chem. 2006 Feb 1;78(3):718-25. doi: 10.1021/ac0512709.
A rectilinear ion trap (RIT) mass analyzer was incorporated into a mass spectrometer fitted with an electrospray ionization source and an atmospheric pressure interface. The RIT mass spectrometer, which was assembled in two different configurations, was used for the study of biological compounds, for which performance data are given. A variety of techniques, including the use of a balanced rf, elevated background gas pressure, automatic gain control, and resonance ejection waveforms with dynamically adjusted amplitude, were applied to enhance performance. The capabilities of the instrument were characterized using proteins, peptides, and pharmaceutical drugs. Unit resolution and an accuracy of better than m/z 0.2 was achieved for mass-to-charge (m/z) ratios up to 2000 Th at a scan rate of approximately 3000 amu/(charge.s) while reduced scan rates gave greater resolution and peak widths of less than m/z 0.5 over the same range. The mass discrimination in trapping externally generated ions was characterized over the range m/z 190-2000 and an optimized low mass cutoff value of m/z 120-140 was found to give equal trapping efficiencies over the entire range. The radial detection efficiency was measured as a function of m/z ratio and found to rise from 35% at low m/z values to more than 90% for ions of m/z 1800. The way in which the ion trapping capacity depends on the dc trapping potential was investigated by measuring the mass shift due to space charge effects, and it was shown that low trapping potentials minimize space charge effects by increasing the useful volume of the device. The collision-induced dissociation (CID) capabilities of the RIT instrument were evaluated by measuring isolation efficiency as a function of mass resolution as well as measuring peptide CID efficiencies. Overall CID efficiencies of more than 60% were easily reached, while isolation of an ion with unit resolution at m/z 524 was achieved with high rejection (>95%) of the adjacent ions. The overall analytical capabilities of the ESI-RIT instrument were demonstrated with the analysis of a mixture of pharmaceutical compounds using multiple-stage mass spectrometry.
将一个直线离子阱（RIT）质量分析仪集成到一台配备电喷雾电离源和大气压接口的质谱仪中。以两种不同配置组装的RIT质谱仪用于生物化合物的研究，并给出了相关性能数据。应用了多种技术，包括使用平衡射频、提高背景气体压力、自动增益控制以及具有动态调整幅度的共振喷射波形，以提高性能。使用蛋白质、肽和药物对该仪器的性能进行了表征。在扫描速率约为3000 amu/（电荷·秒）时，对于质荷比（m/z）高达2000 Th的离子，实现了单位分辨率且精度优于m/z 0.2，而在相同范围内，降低扫描速率可获得更高的分辨率且峰宽小于m/z 0.5。在m/z 190 - 2000范围内对捕获外部产生离子时的质量歧视进行了表征，发现优化后的低质量截止值为m/z 120 - 140，可在整个范围内提供相等的捕获效率。测量了径向检测效率作为m/z比的函数，发现其从低m/z值时的35%上升至m/z 1800离子时的90%以上。通过测量空间电荷效应引起的质量偏移，研究了离子捕获能力与直流捕获电势的关系，结果表明低捕获电势通过增加装置的有效体积来最小化空间电荷效应。通过测量隔离效率作为质量分辨率的函数以及测量肽的碰撞诱导解离（CID）效率，对RIT仪器的CID能力进行了评估。总体CID效率轻松超过60%，同时在m/z 524处实现了单位分辨率的离子隔离，对相邻离子的排斥率很高（>95%）。通过使用多级质谱对药物化合物混合物进行分析，展示了电喷雾电离 - RIT仪器的整体分析能力。
