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- Posts: 3
- Joined: Thu Apr 17, 2025 2:10 pm
Hi everyone,
I'm new with GC-MSMS methods and have the following problem with my Trace 1310/TSQ 8000:
I injected one solution containing seven standards (most of them are fatty acid ethyl esters) several times and measured them with the same oven/injector program and MS temperatures... The only difference was the MS mode: scan, SIM and SRM. In scan and SIM mode, I had some fluctuations (<10%) of the peak areas from run to run, but no problems within a run (peak ratios stayed the same, also <5% variation). In SRM mode, I have variations within one run, depending on the retention time. For example, compound 1-4 eluting at 15-19 min have constant peak ratios and compound 5-6 eluting at 22-23 min have the same ratios, but for example, compound 1 and 6 (both fatty acid ethyl esters) have different peak ratios over nine measurements (in one sequence) with 20-30% variation.
I tried retuning before starting the sequence, but it didn't solve the problem. I also tried the acquisition timed mode (small windows for every compound) as well as measuring all important transitions (7) over the whole time, but it also did not affect the peak ratios. The ion ratios stay nearly the same, so this is not the problem. Since I only measure standards in hexane, there could be no matrix effect, either.
Is it normal for intensities to fluctuate that much in one single run when measuring in SRM mode? Or is there anything I can do?
Thank you for any help or information about that problem!
I'm new with GC-MSMS methods and have the following problem with my Trace 1310/TSQ 8000:
I injected one solution containing seven standards (most of them are fatty acid ethyl esters) several times and measured them with the same oven/injector program and MS temperatures... The only difference was the MS mode: scan, SIM and SRM. In scan and SIM mode, I had some fluctuations (<10%) of the peak areas from run to run, but no problems within a run (peak ratios stayed the same, also <5% variation). In SRM mode, I have variations within one run, depending on the retention time. For example, compound 1-4 eluting at 15-19 min have constant peak ratios and compound 5-6 eluting at 22-23 min have the same ratios, but for example, compound 1 and 6 (both fatty acid ethyl esters) have different peak ratios over nine measurements (in one sequence) with 20-30% variation.
I tried retuning before starting the sequence, but it didn't solve the problem. I also tried the acquisition timed mode (small windows for every compound) as well as measuring all important transitions (7) over the whole time, but it also did not affect the peak ratios. The ion ratios stay nearly the same, so this is not the problem. Since I only measure standards in hexane, there could be no matrix effect, either.
Is it normal for intensities to fluctuate that much in one single run when measuring in SRM mode? Or is there anything I can do?
Thank you for any help or information about that problem!
