A common method for reducing the size of the data without discarding information when saving mass spectrometry data is to only store data points where the intensity is greater than zero. This can result in the data points in any two spectra containing different m/z values (for example in one spectrum there may be a peak at 798.55 and therefore a corresponding data point, but in the next spectrum this peak was not detected and therefore this value is not present in the spectrum).
This method of storing spectra can cause issues for spectral visualisation, combining spectra (such as calculating an average, or generating a ‘data cube’) or performing preprocessing methods (such as smoothing or baseline correction).
Preprocessing Workflow Editor
by selecting Edit
button in Spectral Preprocessing
panel.Zero Filling
method (see Choosing the most appropriate method section below) and click the adjacent +
button.OK
to close the Edit Preprocesing Method
window and then OK
again to close the Preprocessing Workflow Editor
. The chosen method(s) will now be automatically applied to any viewed spectrum.The most appropriate method to use depends on the data and the desired next step in the processing workflow. The methods included in SpectralAnalysis are described below.
Specify a m/z bin size, and a m/z range. The resulting m/z axis then spans the specified m/z range consisting of equally sized bins. All data points which fall within one of the bins are then added together to generate the resulting spectrum.
Specify a PPM bin size, and a m/z range. The resulting m/z axis then spans the specified m/z range consisting of bins of increasing size (each bin has a constant size in PPM, but as PPM is proportional to m/z, the bin size increases as m/z increases). All data points which fall within one of the bins are then added together to generate the resulting spectrum.
Specify a m/z bin size, and a m/z range. The resulting m/z axis then spans the specified m/z range consisting of equally sized bins. All data points are then interpolated onto the new m/z axis (linear interpolation).
Specify a PPM bin size, and a m/z range. The resulting m/z axis then spans the specified m/z range consisting of bins of increasing size (each bin has a constant size in PPM, but as PPM is proportional to m/z, the bin size increases as m/z increases). All data points are then interpolated onto the new m/z axis (linear interpolation).