sr {rNMR}R Documentation

Chemical shift referencing


GUI for adjusting chemical shift references in one or more spectra.




Displays a chemical shift referencing GUI. Changes are only applied to files selected from the files list. Double-clicking on a file name within the files list will switch the current spectrum to the file selected. To set a chemical shift reference, enter a numeric value for the shift (or use the Get shift button to use a point in the current spectrum) and then define the reference point by pressing the Point button or the Region button. In both cases, the selected spectra must have the same nuclei and number of points and dimensions as the current spectrum.

The Point button allows the reference point to be selected manually by clicking on a point within the main plot window. The corresponding position (in ppm) is then used as a chemical shift reference for the selected spectra.

The Region button defines the reference point by the location of the maximum intensity observed within a select region. Two successive mouse clicks indicate opposite corners of the region being defined.

The shift referencing GUI also allows shifts to be adjusted manually (without a reference) using the arrow buttons. The value for the adjustment increment is in ppm and must be a positive number. Manual shift adjustment is best used to align spectra in conjunction with the overlay tool (see ol). Chemical shift referencing should be performed prior to designating ROIs (see roi). Unlike peak lists, ROI tables are not updated after chemical shift referencing.

One-dimensional spectra may be referenced automatically using the Auto button. Automatic referencing sets the chemical shift of the furthest upfield peak with an intensity above the 1D threshold (see pp) to 0 ppm. The Default button restores the original (as collected) shift reference to the selected spectra.


Ian A. Lewis, Seth C. Schommer

See Also

pp for peak picking; roi for ROI's; ol for overlays; rNMR for other rNMR help topics.

[Package rNMR version 1.1.9 Index]