THEORETICAL SIGNAL-TO-NOISE RATIO AND MASS RESOLUTION IN FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY

Theoretical expressions are derived for relative single-to-noise ratio in Fourier transform ion cyclotron resonance (FT-ICR) mass spectroscopy, for arbitrary sample pressure and arbitrary fraction of the total duty cycle spent in observing the time-domain FT-ICR signal. Plots of signal-to-noise ratio and resolution as functions of acquisition period at fixed sample pressure show that for optimal duty cycle, signal-to-noise ratio is maximized at a short acquisition period, while resolution is maximized at a long acquisition period; a suggested experimentally optimal acquisition period is 2-3 times as long as the FT-ICR time-domain signal damping constant. The present calculations and graphs confirm that the high-resolution capability inherent to fixed magnetic field FT-ICR operation can be realized while retaining most of the signal-to-noise enhancement devolving from the Fellgett multichannel advantage of Fourier data reduction. FT-ICR provides particularly convenient tradeoff of signal-to-noise ratio vsresolution, simply by varying the acquisition period at a given sample pressure. Finally, the common features of signal detection in ICR and in nuclear magnetic resonance are tabulated and discussed. © 1979, American Chemical Society. All rights reserved.