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November 20-21, 2019 | Berlin, Germany
OF EXCELLENCE
IN INTERNATIONAL
MEETINGS
alliedacademies.comYEARS
ANALYTICAL CHEMISTRY AND
CHROMATOGRAPHY METHODS
2
nd
International Conference on
Analytical Chemistry 2019
MASS ACCURACY OF MULTI-REFLECTING TOFMS
Anatoly Verenchikov
Mass Spectrometry Consulting Ltd., Montenegro
A
nalytical chemistry becomes more and more alert of the importance of mass accuracy in mass spectral
measurements. With development of new data processing algorithms, true specificity and the separation
power of mass spectral measurements is primarily limited by mass accuracy rather than by the resolving power.
Sub-ppmmass accuracy is desired in proteomics for reduced number of incorrect identifications (an increase in
the confidence of hits) and it would extend the mass range and the elemental diversity of compound identifi-
cation in other areas of mass spectral analyses. As demonstrated on GCxGC-MS case [1], the separation capac-
ity of hybrid separation methods improves with mass accuracy. As been shown in [2], accurate mass defects,
in-large, correlate with mobility shifts and in this sense precise mass measurements duplicate the mobility
separations. Currently, commercial high-resolution instruments –time-of-flight MS, ICR FTMS and electrostatic
traps – are just approaching a barrier of sub-ppm mass accuracy. Back in 2006, multi-reflecting time-of-flight
mass spectrometers (MR-TOF) were demonstrated to reach 1 Million resolving power [3] for a narrow mass
range. At full mass range, the resolving power R is limited by the instrument size with typical R=200,000 to
300,000 [4], meaning that mass spectral peaks are 3-5ppm wide. With detected ion fluxes up to 1E+8ion/s, ion
statistics potentially allows reaching low 1ppb mass scatter at sub second spectral acquisition. However, the
true mass accuracy with internal calibration still remains in the order of 0.1ppm (i.e. 100ppb). The presentation
will discuss several already recognized limiting factors: In-spectra ion statistical limit, limiting mass accuracy
at low intensity signals or at fast spectral acquisitions; diversity of not fully resolved isobars from chemical
background systematic curvature and oscillations of mass calibration curve, produced by finite rise time and
oscillations induced on accelerator electrodes: Slow drifts and higher frequency noise of power supplies; Mass
and charge dependent parameters of ion beam in front of MRTOF; Effects of nanoampere currents within inter-
faces; Space charge effects within analyzers and Noise and saturation of the data system. Most of those factors
can be avoided or at least accurately recognized for producing reliable measurement results.
References
1.
Verenchikov et. al, IMSC 2014, MOS01-05
2.
Kozlov
ey.al,ASMS 2014
3.
Verenchikov
et.al, Technical Physics, Vol. 50, No. 1, 2005, pp. 82–86.
4.
Verenchikov
et.al, JASCM, 2017, 6, 1-22.
Anatoly Verenchikov, J Chem Tech App 2019, Volume 3
Journal of Chemical Technology and Applications | Volume 3