Electrically Compensated Fourier Transform Ion Cyclotron Resonance Cell for Complex Mixture Mass Analysis

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• 作者：Nathan K. Kaiser ; Joshua J. Savory ; Amy M. McKenna ; John P. Quinn ; Christopher L. Hendrickson ; Alan G. Marshall
• 刊名：Analytical Chemistry
• 出版年：2011
• 出版时间：September 1, 2011
• 年：2011
• 卷：83
• 期：17
• 页码：6907-6910
• 全文大小：733K
• 年卷期：v.83,no.17(September 1, 2011)
• ISSN：1520-6882

文摘

Complex natural organic mixtures such as petroleum require ultrahigh mass spectral resolution to separate and identify thousands of elemental compositions. Here, we incorporate a custom-built, voltage-compensated ICR cell for Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), based on a prior design by Tolmachev to produce optimal mass resolution. The compensated ICR cell installed in a custom-built 9.4 T FTICR mass spectrometer consists of seven cylindrical segments with axial proportions designed to generate a dc trapping potential that approaches an ideal three-dimensional axial quadrupolar potential. However, the empirically optimized compensation voltages do not correspond to the most quadrupolar trapping field. The compensation electrodes minimize variation in the reduced cyclotron frequency by balancing imperfections in the magnetic and electric field. The optimized voltages applied to compensation electrodes preserve ion cloud coherence for longer transient duration by approximately a factor of 2, enabling separation and identification of isobaric species (compounds with the same nominal mass but different exact mass) common in petroleum, such as C₃ vs SH₄ (separated by 3.4 mDa) and SH₃¹³C vs ¹²C₄ (separated by 1.1 mDa). The improved performance of the ICR cell provides more symmetric peak shape and better mass measurement accuracy. A positive ion atmospheric pressure photoionization (APPI) petroleum spectrum yields more than 26鈥?00 assigned peaks, Fourier-limited resolving power of 800鈥?00 at m/z 500 (6.6 s transient duration), and 124 part per billion root mean square (rms) error. The tunability of the compensation electrodes is critical for optimal performance.