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OpenLab CDS Peak Identification in New Sequences

Question asked by jwycech on Nov 18, 2020
Latest reply on Nov 24, 2020 by martin.adams

Hi all,

 

I am analyzing petroleum samples with a GC-MSD and I'm having trouble getting the software to identify peaks using OpenLab CDS (v. 2.5). I have optimized the data processing method for peak IDs based on standards and unknowns for a particular sequence, but when I upload a different sequence I cannot get the processing method to correctly ID some peaks even after I update the expected retention time (RT) for the time reference peak(s).

 

I have assigned 1-2 time reference peaks with large absolute RT windows (1.5-4 min) for each EIC. These reference peaks are easily identifiable and the large window should accommodate run-to-run RT shifts. The other peaks of interest have smaller absolute RT windows (0.1-0.2 min). In some cases, I made the RT window larger (~0.3 min) to ensure that the peak was correctly identified (see example below), but the software still refuses to ID the peak correctly. 

 

For example, in the chromatogram below the peak of "C25 22S Tricyclic" should be the left peak in the doublet (~44.25 min). As defined in the Compound ID table below, the targeted peak is the first peak within the RT window, but is still not assigned correctly. I also changed MS purity to 0% in the Compound Spectra section of the method to ensure this issue was not caused by a spectra mismatch between the reference and sample. 

 

EIC chromatogram of  two peaks, one of which the software considers missing (labeled in red)

 

Compound Identification table showing the details for the two peaks

 

I realize I could right click on the peak at 44.25 min, go to Assign Peak..., select the peak name, and check "update RT in the method". This will fix the issue in this sample but when I "Reprocess All", it leads to new misidentifications of the peak in other samples. Do I have to create a new processing method for each sample and update expected RTs for all "missing" (i.e. unidentified) peaks? That seems laborious and something that should be resolved using time reference peaks and appropriate RT windows.

 

Any advice you can give would be greatly appreciated. Thank you!

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