- Background height: minimum intensity at peak boundaries
- Background area (named Background):
- rectangular area of background height times the length between peak boundaries (pre-v1.4 patch 1)
- total integrated area of the minimum of background height and intensity at each point (v1.4 patch 1 and later)
(Note: the unit of RT time is second for this calculation)
- Peak height (named Height): maximum intensity between peak boundaries minus background height
- Peak area (named Area): total integrated area within peak boundaries minus background area (Note: the unit of RT time is second for this calculation)
- area can be zero and background greater than total raw area (pre-v1.4 patch 1)
- area plus background always equals raw area (v1.4 patch 1 and later)
NOTE: Skyline uses points that have been linear interpolated from the raw data onto a uniform interval over the duration of the chromatogram in detecting its peak boundaries and calculating its peak areas. These are also the points Skyline displays in its chromatogram graphs. Skyline uses several types of smoothing (1st derivative, 2nd derivative and Savitzky-Golay) in order to place its automatically calculated peak boundaries. These smoothed curves are available for display in the Skyline chromatogram graphs. Skyline does not, however, use smoothed data in calculating peak areas (or area under the curve - AUC). It always uses the raw interpolated points presented in the unsmoothed graphs.
Example of calculation of peak height and background area:
Note: with v1.4 patch 1 and higher the light blue areas are not included in the background area.