Parts-Per-Billion Fourier Transform Ion Cyclotron Resonance Mass Measurement Accuracy with a “Walking” Calibration Equation
2011; American Chemical Society; Volume: 83; Issue: 5 Linguagem: Inglês
10.1021/ac102943z
ISSN1520-6882
AutoresJ. Savory, Nathan K. Kaiser, Amy M. McKenna, Feng Xian, Greg T. Blakney, Ryan P. Rodgers, Christopher L. Hendrickson, Alan G. Marshall,
Tópico(s)Nuclear Physics and Applications
ResumoIon cyclotron resonance frequency, f, is conventionally converted to ion mass-to-charge ratio, m/z (mass "calibration") by fitting experimental data spanning the entire detected m/z range to the relation, m/z = A/f + B/f(2), to yield rms mass error as low as ~200 ppb for ~10,000 resolved components of a petroleum crude oil. Analysis of residual error versus m/z and peak abundance reveals that systematic errors limit mass accuracy and thus the confidence in elemental composition assignments. Here, we present a calibration procedure in which the spectrum is divided into dozens of adjoining segments, and a separate calibration is applied to each, thereby eliminating systematic error with respect to m/z. Further, incorporation of a third term in the calibration equation that is proportional to the magnitude of each detected peak minimizes systematic error with respect to ion abundance. Finally, absorption-mode data analysis increases mass measurement accuracy only after minimization of systematic errors. We are able to increase the number of assigned peaks by as much as 25%, while reducing the rms mass error by as much as 3-fold, for significantly improved confidence in elemental composition assignment.
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