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- Posts: 2
- Joined: Sun Sep 24, 2017 2:55 pm
I am relatively new to HPLC/LCMS, and I am currently working on the quantification of certain terpenes/alkaloids compounds in plants. My laboratory has been using SCIEX 6500 triple Quad and recently acquired Thermo TSQ Quantiva triple quad. We have established many methods in SCIEX that worked satisfactorily and now trying to transfer the method established in 6500 to Quantiva. However, I have been having unstable signal problems in optimizing the condition in TSQ Quantiva.
The system I am using is a Thermo Dionex Ultimate 3000 UPLC and TSQ Quantiva triple quad. I have already tuned my compounds in Quantiva and manual tuning by infusing the standard compounds into the MS seems normal with stable signal of RSD<15%. However, when I tried to setup the whole program with LC and MRM conditions, the signals of all my target analytes fluctuates, say every 5-10 injections, there would be one injection that the signals of all analytes became nearly half. But when I tried to do replicate injections of reserpine, everything seems alright.
I have checked the UPLC part but the flow rate, pressure, etc looks normal. I have also cleaned the source, needles etc, but that doesn't improve much. Previously I have got relatively more stable signal with the same conditions for my target analytes, but then after doing replicate injections for nearly 60 times, the instrument never became stable again. I have tried all the other analytes that worked previously but still everything went unstable except reserpine.
I have been encountering this problem for several months but still cannot solve it. Would be grateful if anyone can share their expertise here.
Many thanks!