Resolution and signal-to-noise in Fourier transform mass spectrometry

White, Robert L.; Ledford, Edward B.; Ghaderi, Sahba.; Wilkins, Charles L.; Gross, Michael L.

doi:10.1021/ac50059a034

Cited by 51 publications

(16 citation statements)

References 29 publications

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“…As a result, the mass resolving power increased over a m/z range of 1084 ([Arg]8-vasopressin) to ~12,500 (cytochrome C), a realistic range for most biological mass spectrometric applications, especially when using electrospray ionization. For spectral peaks containing the same number of ions, S/N increased with increasing mass resolving power, as was first described in 1980 [33]. The increase in S/N afforded by trap compensation is approximately an order of magnitude.…”

Section: Discussionsupporting

confidence: 53%

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Ion behavior in an electrically compensated ion cyclotron resonance trap

Brustkern

Rempel

Gross

2011

International Journal of Mass Spectrometry

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We recently described a new electrically compensated trap in FT ion cyclotron resonance mass spectrometry and developed a means of tuning traps of this general design. Here, we describe a continuation of that research by comparing the ion transient lifetimes and the resulting mass resolving powers and signal-to-noise (S/N) ratios that are achievable in the compensated vs. uncompensated modes of this trap. Transient lifetimes are ten times longer under the same conditions of pressure, providing improved mass resolving power and S/N ratios. The mass resolving power as a function of m/z is linear (log-log plot) and nearly equal to the theoretical maximum. Importantly, the ion cyclotron frequency as a function of ion number decreases linearly in accord with theory, unlike its behavior in the uncompensated mode. This linearity should lead to better control in mass calibration and increased mass accuracy than achievable in the uncompensated mode.

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Section: Discussionsupporting

confidence: 53%

“…Along with an increase in mass resolving power comes an increase in S/N obtained by decreasing the spread in frequencies of a single m/z at a constant observation time. Given that peak area is a measure of ion number, the same ion count at improved mass resolving power gives an increase in S/N [33]. …”

Section: Resultsmentioning

confidence: 99%

Ion behavior in an electrically compensated ion cyclotron resonance trap

Brustkern

Rempel

Gross

2011

International Journal of Mass Spectrometry

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“…In addition, the relationship of important instrument performance metrics can be affected by factors with no- or convoluted field dependences. For example, the relationship between mass accuracy and resolution is blurred by anything that affects ideal peak shapes [15–17]. …”

Section: Introductionmentioning

confidence: 99%

Transformative effects of higher magnetic field in Fourier transform ion cyclotron resonance mass spectrometry

Karabacak

Easterling

Agar

et al. 2010

J. Am. Soc. Mass Spectrom.

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The relationship of magnetic field strength and Fourier transform ion cyclotron resonance mass spectrometry performance was tested using three instruments with the same design but different fields of 4.7, 7, and 9.4 tesla. We found that the theoretically predicted "transformative" effects of magnetic field are indeed observed experimentally. The most striking effects were that mass accuracy demonstrated ϳsecond to third order improvement with the magnetic field, depending upon the charge state of the analyte, and that peak splitting, which prohibited automated data analysis at 4.7 T, was not observed at 9.4 T. Numerous performance parameters in FT-ICR MS are predicted to improve with magnetic field, including linear improvements in mass resolving power and acquisition speed, and higher order improvements in mass accuracy, dynamic range, kinetic energy, and peak coalescence [2][3][4][5][6][7]. All of these parameters combine to determine the figure of merit of a mass analyzer, but not in a manner that is easily predicable. Improving FT-ICR MS performance is critical in many fields such as proteomics, petroleomics, and MALDI imaging, and in many cases enables, rather than improves, analytical capabilities. In practice, however, a component with no a priori field dependence, for example field homogeneity [8] vacuum strength, or acquisition speed, which set fundamental limits on resolution [2], or a phenomenon with a convoluted electrical and magnetic field dependence such as peak coalescence [9] or phase locking [7, 10 -14], can become the limiting factor and the determinant of performance. In addition, the relationship of important instrument performance metrics can be affected by factors with no-or convoluted field dependences. For example, the relationship between mass accuracy and resolution is blurred by anything that affects ideal peak shapes [15][16][17].There are isolated literature examples of what Marshall terms the "transformative effects" of higher magnetic fields. For example, post processing of 14.7 T FTMS spectrum to simulate a 7 T FTMS spectrum revealed that three compounds that were identifiable at 14.7 T appeared to be a single compound at 7 T [18]. In another example, the instrument's sensitivity for a complex and highly charged sample (29 kDa protein dissociation products) significantly increased when going from 6 T to 9.4 T FT-ICR [19]. On the other hand, despite the availability of 15 T instruments, the highest published resolving powers of ϳ8,000,000 (m/z 1148) [20], ϳ17,000,000 (m/z 1084.5) [21], ϳ1,000,000 (m/z 12,360) [22] were acquired (in one case 11 years ago [20]) at 9.4 T or 7 T, illustrating the importance of factors other than magnetic field. While the effects of field homogeneity upon instrument performance have been characterized [8], we are aware of no publication that systematically explores the relationship of FT-ICR MS performance and gross magnetic field. Here, we make an empirical determination of the merit of higher magnetic field, using the same instrument type, the same...

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“…These workers further observed that peak linewidth increases (hence, resolution decreases) as the pressure of the system increases, because of the concurrent increase in "reduced" collision frequency (24,25). This was demonstrated experimentally for a fixed number of ions at a variety of pressures by White and co-workers (26). One of the earliest experimental examples of the high-resolution potential of FTMS is found in report of obtaining a mass spectrum of a mixture of CO, NZ, and ethylene with a ratio of peak frequency to peak width at half-height (mlAm) of 2.5 x lo5 (27).…”

Section: A High-resolution Measurementsmentioning

confidence: 78%

“…These results can be contrasted with McIver's early trapped-cell ICR measurement where resolution of 5700 was obtained at torr (29). Others subsequently have provided additional experimental verification of the ultra-high resolution of FTMS by obtaining resolution of 7.6 X lo5 at mlz 78 (26), 6.0 x lo4 at mlz 1166 (15), and 1.5 x lo6 for the mlz 166 ion from tetrachloroethylene (8). Based upon this series of measurements, Ghaderi and co-workers have predicted unit mass resolution at mlz 20,000 if an 8.5-T magnet were used (30).…”

Section: A High-resolution Measurementsmentioning

confidence: 90%