ARTIFACTS IN FOURIER TRANSFORM MASS SPECTROMETRY

傅里叶变换质谱中的伪影

• 批准号: 7955973
• 负责人: PETER B. O'CONNOR
• 金额: $ 0.47万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2010-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7955973
• 关键词: Amplifiers; Appearance; Biology; Chemicals; Clip; Computer Retrieval of Information on Scientific Projects Database; Custom; Data; Equilibrium; Fourier Transform; Fourier transform ion cyclotron resonance; Frequencies; Funding; Grant; Institution; Ions; Isotopes; Lead; Mass Spectrum Analysis; Medicine; Modeling; Morphologic artifacts; Noise; Process; Radio; Research; Research Personnel; Resources; Sampling; Side; Signal Transduction; Simulate; Source; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Stress; United States National Institutes of Health; Work; analog; base; computerized data processing; design; digital; instrument; interest; mass spectrometer; simulation

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Recent work (Mathur et al., 2008) on a new, higher sensitivity preamplifier design for Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed a number of artifact peaks (spectral features) which do not contain useful chemical information. In order to determine the cause of these artifacts and eliminate them, these severely distorted spectra were compared with similarly distorted signal models (Mathur et al., 2009). C60 was chosen as the compound of interest, whose mass spectra were obtained using the custom built 7T MALDI FT-ICR mass spectrometer. Simulated spectra were generated using a MATLAB script. Three undamped sinusoidal functions were used to model the first three isotopes of C60. It was found that imbalance in the gain or bias of the amplifier could lead to overloading of the analogue to digital converter (ADC) which resulted in appearance of harmonics in the mass spectra. This observation was confirmed by simulation, where clipping of one side of the digital transient led to appearance of multiple harmonics peaks in the simulated spectra. Fold-over peaks due to under-sampling (aliasing) were also apparent for higher order harmonics peaks. It was further shown that severe overloading of the ADC (even when the amplifier is perfectly balanced with no DC offsets) could also cause distortion in the isotopic distribution of ions, which would make the automatic interpretation of the mass spectra difficult. Finally, radio-frequency interference (RFI) noise riding on the ICR signal causing imbalance and/or overloading of the ADC may also induce intermodulations between isotopic peaks and the RFI noise, leading to undesirable artifacts. Thus, the source of several common signal processing artifacts was thereby determined and correlated to RFI noise and saturation of the amplifier and/or the digitizer. Under such conditions, the fast Fourier transform (FFT) generates spectral artifact peaks corresponding to harmonics and mixing frequencies of the real signal peaks and RFI frequencies. While this study was done using the FT-ICR MS data, it is important to stress that these artifacts are inherent to the digitization and FFT process and thus are relevant to any FT-based MS instrument, including the orbitrap and FT ion trap.

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目和 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 对于中心来说，它不一定是研究者的机构。 最近的工作（Mathur 等人，2008）针对傅里叶变换离子回旋共振质谱（FT-ICR MS）的新型、更高灵敏度的前置放大器设计揭示了许多不包含有用化学信息的伪影峰（光谱特征）。为了确定这些伪影的原因并消除它们，将这些严重失真的光谱与类似失真的信号模型进行比较（Mathur 等人，2009）。 选择 C60 作为感兴趣的化合物，其质谱是使用定制的 7T MALDI FT-ICR 质谱仪获得的。使用 MATLAB 脚本生成模拟光谱。使用三个无阻尼正弦函数来模拟 C60 的前三种同位素。研究发现，放大器增益或偏置的不平衡可能导致模数转换器 (ADC) 过载，从而导致质谱中出现谐波。这一观察结果得到了模拟的证实，其中数字瞬态一侧的削波导致模拟频谱中出现多个谐波峰值。对于高阶谐波峰值，由于采样不足（混叠）而导致的折叠峰值也很明显。进一步表明，ADC 的严重过载（即使放大器完全平衡且没有直流偏移）也可能导致离子同位素分布失真，这将使质谱的自动解释变得困难。最后，ICR 信号上的射频干扰 (RFI) 噪声导致 ADC 不平衡和/或过载，也可能引起同位素峰值和 RFI 噪声之间的互调，从而导致不良伪影。因此，确定了几种常见信号处理伪影的来源，并将其与放大器和/或数字化仪的 RFI 噪声和饱和度相关联。在这种情况下，快速傅立叶变换 (FFT) 会生成与真实信号峰值和 RFI 频率的谐波和混合频率相对应的频谱伪影峰值。虽然这项研究是使用 FT-ICR MS 数据完成的，但需要强调的是，这些伪影是数字化和 FFT 过程所固有的，因此与任何基于 FT 的 MS 仪器（包括轨道阱和 FT 离子阱）相关。