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| Titel |
Statistical precision of the intensities retrieved from constrained fitting of overlapping peaks in high-resolution mass spectra |
| VerfasserIn |
M. J. Cubison, J. L. Jimenez |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 6 ; Nr. 8, no. 6 (2015-06-05), S.2333-2345 |
| Datensatznummer |
250116424
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| Publikation (Nr.) |
 copernicus.org/amt-8-2333-2015.pdf |
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| Zusammenfassung |
| Least-squares fitting of overlapping peaks is often needed to separately
quantify ions in high-resolution mass spectrometer data. A statistical
simulation approach is used to assess the statistical precision of the
retrieved peak intensities. The sensitivity of the fitted peak intensities
to statistical noise due to ion counting is probed for synthetic data
systems consisting of two overlapping ion peaks whose positions are
pre-defined and fixed in the fitting procedure. The fitted intensities are
sensitive to imperfections in the m/Q calibration. These propagate as a
limiting precision in the fitted intensities that may greatly exceed the
precision arising from counting statistics. The precision on the fitted peak
intensity falls into one of three regimes. In the "counting-limited
regime" (regime I), above a peak separation χ ~ 2 to 3
half-widths at half-maximum (HWHM), the intensity precision is similar to
that due to counting error for an isolated ion. For smaller χ and
higher ion counts (~ 1000 and higher), the intensity precision
rapidly degrades as the peak separation is reduced ("calibration-limited
regime", regime II). Alternatively for χ < 1.6 but lower ion
counts (e.g. 10–100) the intensity precision is dominated by the additional
ion count noise from the overlapping ion and is not affected by the
imprecision in the m/Q calibration ("overlapping-limited regime", regime
III). The transition between the counting and m/Q calibration-limited regimes
is shown to be weakly dependent on resolving power and data spacing and can
thus be approximated by a simple parameterisation based only on peak
intensity ratios and separation. A simple equation can be used to find
potentially problematic ion pairs when evaluating results from fitted
spectra containing many ions. Longer integration times can improve the
precision in regimes I and III, but a given ion pair can only be moved out
of regime II through increased spectrometer resolving power. Studies
presenting data obtained from least-squares fitting procedures applied to
mass spectral peaks should explicitly consider these limits on statistical
precision. |
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