University of Warwick crest Dr. Mark P. Barrow: Research in mass spectrometry

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FT-ICR calculations

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This page is divided into two sections so that users may calculate the maximum theoretical resolution using different methods. The first section will, after the user has defined the experimental parameters, calculate the theoretical maximum resolution (obtained under ideal conditions, where the signal lasts the entirety of the acquisition time, regardless of how long it is) of a chosen peak, the frequency of the peak of interest, and the acquisition time. The second section will calculate the theoretical maximum resolution and the frequency of a peak of interest when the user has defined the magnetic field strength, the m/z of the peak of interest, and the acquisition time.

The first section is more useful for those wanting information based on actual experimental parameters. By keeping the low m/z limit constant and varying the peak of interest, it is possible to see how the resolution will vary throughout a particular mass spectrum. The acquisition time is determined by the dataset size and twice the sampling frequency (the highest frequency, linked to the lowest m/z, within the detection range of a given mass spectrum), in accordance with the Nyquist theorem.

The second section is more useful for monitoring how resolution varies as a function of magnetic field strength for the same acquisition time or examining how the resolution is adversely affected by damping of the signal to zero before the end of the acquisition time (i.e. this is similar to operating with a shorter acquisition time than actually determined by the experimental parameters).

Note that, in both cases, the maximum resolution is calculated based on ideal conditions, such as a perfect vacuum and no space-charge effects.

1) For a full acquisition time (limited only by experimental parameters):

Parameters:

Dataset size (eg. 256 k, 512 k, 1024 k, etc):

k

Low m/z limit of mass spectrum:

Magnetic field strength:

tesla

m/z of peak of interest:

Results:

Maximum FWHM resolution:

Acquisition time (Tacq):

seconds

Frequency of peak of interest:

Hz

2) For a user-defined acquisition time:

Parameters:

Magnetic field strength:

tesla

m/z of peak of interest:

Acquisition time (Tacq):

seconds

Results:

Maximum FWHM resolution:

Frequency of peak of interest:

Hz