Treatment of Noise in Magnitude-Mode FT-ICR Spectra

Abstract

In FT-ICR spectroscopy it is often desirable to be able to determine ion abundances from the heights of small spectral peaks in the presence of substantial noise. When magnitude-mode transforms are used, the noise gives an apparent baseline shift, and it may be thought appropriate to measure peak heights from this apparent baseline. It is shown here that such a noise correction procedure is inappropriate, and that the peak heights measured from the original, noise-free baseline to the tops of the smoothed peaks give an excellent approximation to the true peak heights. Correction factors for peaks heights are given, which become significant at signal-to-noise ratios below about 3 and which may be useful when spectral accumulation is performed in the frequency domain.