How to correctly use NIST search data base

Question

Good morning everyone, 
 Hope you all had a great new year. 
 
 So, the problem that I'm having is that sometimes, when processing a GCMS run through QUALI Masshunter I find some "unknown" compounds. So far so good. 
 The problem arise when trying to identify it using NIST. because if i double click the peak to select the mass spectra I get two different spectra for the same peak at the same height, see pictures 1 and 2, the first one is the spectra to the left of center and second the spectra to the right 
 
 When using NIST I get two different predictions (as expected) for the two integrations. The question is: which one should I use since both of them are at the highest point? 
 
 thank you in advance, 
 have a great day.

howard_sanford · Accepted Answer

Hi Teruaki , 
 This appears to be scan/SIM GCMS data, where the acquired data alternates between a scan spectrum and a SIM spectrum. You can see what type of spectrum you have extracted by checking the spectrum title.

SIM spectrum will not give meaningful results when searched. 
 If you want to make certain you are only extracting scan spectrum, you can extract a scan TIC by setting the the Extract Chromatograms dialog as follows.

How to correctly use NIST search data base

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