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Mass Spectrometry Instrumentation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Yuan Su, Li-Rong Yu, Thomas P. Conrads, Timothy D. Veenstra
Fourier transform ion cyclotron resonance (FTICR) MS was developed in 1974 but has only recently generated great enthusiasm within the proteomics community (Comisarow and Marshall, 1974). FTICR-MS functions much like an ion-trap analyzer; however, the trap is positioned within a high magnetic field, typically ranging in field strength from 3 to 12 Tesla, as shown in Figure 14.11 (Marshall et al., 1998). Working at higher magnetic fields benefits at least eight parameters related to FTICR performance, the two most critical being resolution and mass accuracy. FTICR instruments have provided the highest resolution, mass accuracy, and sensitivity for peptide and protein measurements so far achieved (Bruce et al., 1999; Dilillo et al., 2017). The magnetic field causes ions captured within the trap to resonate at their cyclotron frequency. A uniform electric field that oscillates at or near the cyclotron frequency of the trap ions is then applied to excite the ions into a larger orbit that can be measured as they pass by detector plates on opposite sides of the trap. The ions within the trap can also be dissociated or ejected, depending on the amount of energy applied. The cyclotron frequencies of all the ions in the trap are then recorded, and the frequency values are converted into m/z values using a Fourier transform.
Molecular-level exploration of properties of dissolved organic matter in natural and engineered water systems: A critical review of FTICR-MS application
Published in Critical Reviews in Environmental Science and Technology, 2023
Mingqi Ruan, Fengchang Wu, Fuhong Sun, Fanhao Song, Tingting Li, Chen He, Juan Jiang
FTICR-MS has several powerful advantages and unique functions to decipher the “black box” of aquatic DOM, benefiting researchers to overcome technical challenges in DOM research. First, FTICR-MS has high resolution and mass accuracy, which achieves peak separation within an extremely small mass unit, overcoming the technical challenges of insufficient molecular information obtained by traditional low-resolution spectrometry. The low-resolution mass spectrum does not allow peak separation to distinguish molecules whose mass changes are less than one mass unit (Sleighter & Hatcher, 2007). However, the mass resolving power of FTICR-MS can reach more than 30000, and the errors in m/z value for single DOM molecule can be less than 0.5 ppm (Qi et al., 2022). Mass differences of a few millidaltons can be distinguished by FTICR-MS, which improves the ability to assign unique DOM molecules (Hsu et al., 2011). Second, electrospray ionization (ESI) of FTICR-MS preserves molecular integrity as much as possible by simplifying injection process, which allows the infusion of aqueous solutions into the mass spectrometer and coupling of mass spectrometry with liquid chromatography (Reemtsma, 2009). This overcomes the technical challenges of destructing and derivatizing DOM molecules and allows the direct analysis of complex DOM. Third, FTICR-MS presents composition and chemical reactions at the molecular level of DOM mixtures. This overcomes the technical challenges of identifying the molecular diversity in composition and transformation of aquatic DOM during various environmental processes. The abundant molecular formulas make FTICR-MS currently one of the few techniques available to observe majority individual DOM components (Minor et al., 2014). Compared to spectroscopy, specific FTICR-MS molecular formulas and indicators help explore deeper understanding of DOM properties. However, several drawbacks and limitations of FTICR-MS also need to be considered (see details in the section 6.1).