synchronous SIM/scan GC/MS

Hello everyone,

I have created a simultaneous SIM/scan method and we're using a HS-SPME-GC-MS system (GC: Agilent 7890 A GC-System; MS: Agilent 5975C Inert XL MSD with Triple-Axis Detector; Software: Chemstation G1701EA E.02.00.493).

We get a TIC (Scan) and a SIM-TIC (last one is shown basically as the summation of den SIM ions and not the separate ion tracks). We try to get the EICs out of the SIM but unfortunately we've failed (Chromatogram -> Extract Chromatogram EIC). If we extract the masses of the SIM we select from the TIC (scan), we get in sum approximately the area of the displayed SIM. Is this normal? We thought it is a 'real' SIM has a higher selectivity and therefore a higher peak area? This method is intended to be suitable not only for known and unknown analytes, but also to visualize analytes that are obscured by 'impurities' in the scan. This works qualitatively, but quantification requires the individual EICs from the SIM, not the summation of the SIM (error propagation through the summation). The problem is that the EICs are usually so small that they can no longer be evaluated correctly. However, we had to choose quite small masses in terms of intensity, because they are very specific and the interfering matrix cannot be separated further and also has many of the fragments.

Thanks for your help!


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