Parts per million mass accuracy on an orbitrap mass spectrometer via lock mass injection into a C-trap
Parts per million mass accuracy on an orbitrap mass spectrometer via lock mass injection into a C-trap
复制标题
DOI：
10.1074/mcp.t500030-mcp200
复制
发表时间：
2005-12-01
影响因子：
7
通讯作者：
Mann, M
中科院分区：
文献类型：
--
作者：
Olsen, JV;de Godoy, LMF;Mann, M
质量准确度是质谱性能的关键参数。TOF仪器可以达到低的百万分之一，FT-ICR仪器能够提供更高的准确度，只要离子数得到很好的控制。在这里，我们展示了亚ppm的质量精度上的线性离子阱耦合通过一个无线电频率仅存储陷阱（C-陷阱）的轨道阱质谱仪（LTQ轨道阱）。在获取光谱之前，首先将源自环境空气的背景离子转移到C阱。然后将形成MS或MSn光谱的离子加入到该物质中，并将所有离子注入轨道阱进行分析。通过校正质量偏移对“锁定质量”进行真实的重新校准，消除了与质量标尺校准相关的质量误差。剩余的质量误差主要是由于弱信号引起的不完美峰，并通过对LC峰上的质量测量进行平均（按信号强度加权）来解决。对于蛋白质组学中的肽数据库搜索，我们引入了可变质量容差，并实现了0.48 ppm（标准偏差0.38 ppm）的平均绝对质量偏差和小于2 ppm的最大偏差。对于串联质谱，我们表现出类似的高质量的准确性，并讨论其对数据库搜索的影响。紧凑型仪器中的高常规质量精度将显著提高肽和小分子鉴定的确定性。
Mass accuracy is a key parameter of mass spectrometric performance. TOF instruments can reach low parts per million, and FT-ICR instruments are capable of even greater accuracy provided ion numbers are well controlled. Here we demonstrate sub-ppm mass accuracy on a linear ion trap coupled via a radio frequency-only storage trap (C-trap) to the orbitrap mass spectrometer (LTQ Orbitrap). Prior to acquisition of a spectrum, a background ion originating from ambient air is first transferred to the C-trap. Ions forming the MS or MSn spectrum are then added to this species, and all ions are injected into the orbitrap for analysis. Real time recalibration on the "lock mass" by corrections of mass shift removes mass error associated with calibration of the mass scale. The remaining mass error is mainly due to imperfect peaks caused by weak signals and is addressed by averaging the mass measurement over the LC peak, weighted by signal intensity. For peptide database searches in proteomics, we introduce a variable mass tolerance and achieve average absolute mass deviations of 0.48 ppm ( standard deviation 0.38 ppm) and maximal deviations of less than 2 ppm. For tandem mass spectra we demonstrate similarly high mass accuracy and discuss its impact on database searching. High and routine mass accuracy in a compact instrument will dramatically improve certainty of peptide and small molecule identification.