Department of Chemistry, University of Warwick, Coventry, UK.
J Am Soc Mass Spectrom. 2011 Jan;22(1):138-47. doi: 10.1007/s13361-010-0006-7. Epub 2011 Jan 28.
FT-ICR mass spectrometry has been limited to magnitude mode for almost 40 years due to the data processing methods used. However, it is well known that phase correction of the data can theoretically produce an absorption-mode spectrum with a mass-resolving power that is as much as twice as high as conventional magnitude mode, and that it also improves the quality of the peak shape. Temporally dispersed frequency sweep excitation followed by a time delay before detection results in a steep quadratic variation in the signal phase with frequency. Viewing this, it is possible to find the correct phase function by performing a quadratic least squares fit, modified by iterating through phase cycles until the correct quadratic function is found. Here, we present a robust manual method to rotate these signals mathematically and generate a "phased" absorption-mode spectrum. The method can, in principle, be automated. Baseline correction is also included to eliminate the accompanying baseline drift. The resulting experimental FT-ICR absorption-mode spectra exhibit a resolving power that is at least 50% higher than that of the magnitude mode.
傅里叶变换离子回旋共振质谱仪由于所使用的数据处理方法，在过去的 40 年中一直局限于幅度模式。然而，众所周知，通过对数据进行相位校正，可以在理论上产生具有比传统幅度模式高两倍的质量分辨率的吸收模式谱，并且还可以改善峰形的质量。在检测之前，经过时间分散的频率扫描激发和时间延迟，导致信号相位随频率呈陡峭的二次变化。从这个角度来看，可以通过执行二次最小二乘拟合来找到正确的相位函数，通过迭代相位循环来修改，直到找到正确的二次函数。在这里，我们提出了一种强大的手动方法来对这些信号进行数学旋转，并生成一个“相”吸收模式谱。该方法原则上可以自动化。还包括基线校正以消除伴随的基线漂移。得到的实验傅里叶变换离子回旋共振吸收模式谱的分辨率至少比幅度模式高 50%。
