Application of Online Liquid Chromatography 7 T FT-ICR Mass Spectrometer Equipped with Quadrupolar Detection for Analysis of Natural Organic Matter

Abstract

In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), combined with quadrupolar detection (QPD), was applied for online liquid chromatography (LC) MS analysis of natural organic matter (NOM). Although FT-ICR MS has emerged as an important analytical technique to study NOM, there are few previous reports on online LC FT-ICR MS analysis of NOM due to the long acquisition time (2-8 s) required to obtain high-resolution mass spectra. The QPD technique provides a critical advantage over the conventional dipolar detection (DPD) technique for LC-MS analysis because a spectrum with the same resolving power can be obtained in approximately half the acquisition time. QPD FT-ICR MS provides resolving powers ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mfrac><mml:mrow><mml:mi>m</mml:mi></mml:mrow><mml:mrow><mml:mi>Δ</mml:mi><mml:msub><mml:mrow><mml:mi>m</mml:mi></mml:mrow><mml:mrow><mml:mn>50</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:mfrac></mml:mrow></mml:math> ) of ∼300000 and 170000 at m/ z 400 with acquisition times per scan of 1.2 and 0.8 s, respectively. The reduced acquisition time per scan allows increased number of acquisitions in a given LC analysis time, resulting in improved signal to noise ( S/ N) ratio and dynamic range in comparison to conventional methods. For example, 40% and 100% increases in the number of detected peaks were obtained with LC QPD FT-ICR MS, in comparison to conventional LC DPD FT-ICR MS and direct-injection FT-ICR MS. It is also possible to perform more quantitative comparison and molecular level investigation of NOMs with 2 μg of a NOM sample. The data presented herein demonstrate a proof of principle that QPD combined with LC FT-ICR MS is a sensitive analytical technique that can provide comprehensive information about NOM.