Max Height minyg98  2021-07-15
 

Hi, Skyline team

Is the value of max height of a peptide coming from the highest point in the borderline I set?
I thought the max height in the picture attached was around 1.2e5, but when I checked in the csv file, it was 4.3e4

-Minyeong

 
 
Nick Shulman responded:  2021-07-15
Here is a web page that describes how Skyline calculates peak height and background:
https://skyline.ms/wiki/home/software/Skyline/page.view?name=tip_peak_calc

The "background" is the lowest intensity of the chromatogram at either the start or end of the peak. The "height" value that Skyline reports is the raw height minus the background.
The reason that the height that you are seeing is so much less than you expect is that the intensity at the start and end of that peak is very high.

-- Nick
 
minyg98 responded:  2021-07-15
Nick, thanks for the help!

In your powerpoint "Triggered acquisition support", it says background subtraction does not happen if Triggered Acquisition is turned on.

Is this applied only when calculating area?

-Minyeong
 
Nick Shulman responded:  2021-08-04
(Sorry for the slow response)

When the Triggered Acquisition checkbox is checked, background subtraction does not happen for either area or height.
Are you seeing any cases where Triggered Acquisition is turned on and it looks like background is being subtracted from the Max Height value?

Note that the peak Height and Max Height values are always going to be a little bit smaller than the actual maximum intensity point along the chromatogram. This is because all of the area and height calculations that Skyline does are done on "interpolated" chromatograms, and not original chromatogram.
That is, when Skyline is doing peak finding, the first thing that Skyline does is resample the points along the chromatogram so that the times of all of the points along the chromatogram are evenly spaced. This has a small effect on the areas and heights that Skyline reports. You can see the difference between the raw and interpolated chromatograms by right-clicking on a chromatogram and choosing "Transform > None" or "Transform > Interpolated".

Let me know if it looks like Skyline is getting the wrong numbers anywhere.
-- Nick