2- dimension gc/fid/ms 8890/5977C

Hello. We have a 2- dimension gc/fid/ms 8890/5977C with a masshunter software. Our aim is to quantify molecular markers (e.g. 1,3,5-Tri-tert - Butylbenzene) used in gasoil to trace fraud. For quantitation we use a sim method (Quantification sim 231 and qualification sim 246 for the aforementioned molecule). We spot the retention time in the first column with a solution of the marker in o-xylene by using the FI detector and then we make a baseline in ms by using standards of the marker in diesel. Our heartcut window is 0.2 min around the retention time.  We achieve a very good linearity but our baselines differ when we use different substrates for the standards (different types of diesel : ligher and heavier). Both sets of standards run under repeatability conditions. We tried to broaden our window to 0.24 min (our instructions is not to go higher than 0.2 min) but we did not see any difference.

Do you have any suggestions?

Furthermore, when we tried the scan method (m/z from 50 to 500, different N, Gain 1, threshold 150, trace identification not checked) we didn’t see any peak in the ms chromatogram, although in the EI we spotted the sims 261 and 246 at the time period we expected the elution of the marker. The standard concentration we used was at the upper side of our calibration curve. We kept the same split and injection volume as in the sim method.

What can we do in order to have a peak of the marker in the ms chromatogram?

Thank you

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