Baseline correction with BF and FR
It is important to understand the differences among the choices for baseline correction. The page illustrates the results of 2 similar commands, BF (Baseline Flatten) and FR (Flatten Region). Both remove DC and linear tilt within the current Zoom limits, but they differ in how the remaining parts of the spectrum are affected.
Both commands act by adjusting the Zoom region to bring both ends of the region to zero. FR does not alter parts of the spectrum outside the chosen Zoom region. This can result in severe discontinuities at the ends of the Zoom region. BF avoids these discontinuities by applying a DC offset to the parts of the spectrum on each end of the Zoom region, such that the baseline remains continuous. It is important to understand that applying correction with BF will change the baseline of the entire spectrum, which will affect integrals.
Start with a spectrum with a severely rolling baseline.
A small section of the spectrum is selected with Zoom. (Note that it is not necessary to expand display to these Zoom limits.)
Results of applying FR.
Results of applying BF. (Same spectrum and same Zoom limits.)
2A To Average This allows the user to specify how many points are averaged at each end of the Zoom region to determine the adjustment required to flatten the chosen region.
FB interactive polynomial baseline correction
QB quick (non-interactive) polynomial baseline correction
BC Baseline Correction removes DC and tilt of the entire spectrum.
ID – Baseline correction from within the integration subroutine. A subcommand within integration allows DC and tilt to be corrected while viewing the integral trace. If done on a zoom region, rather than the entire spectrum, the result is similar to BF, in that the other parts of the spectrum are adjusted to avoid baseline discontinuities.
Last updated: 6/13/07.