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- Posts: 5
- Joined: Sat Nov 12, 2016 12:00 pm
The LC-MS system I am using is ABsiex API3000 coupled with Water Acquity UPLC and the column is Hypercarb 3um 1.0*100mm. The problem I encountered recently is after running first three purified biological samples, the peak areas of standards dropped to only 50% and then after another three samples, the peak areas dropped to 30~40%, compared to the standard injected before running the samples. However, after overnight standby, the peak areas of standards return to almost the same, but the same problem appeared again after running the samples. I have tested 20 consecutive injections of standards only, the peak areas were stable. Could it be the ion source, tubing or column contamination by biological matrix?
The samples I injected were tissue extracts but purified by one LL extraction and two different SPE. And the LC method is first 6 min hold then 5% to 95% ACN gradient followed by two gradient washing step and finally 10 min equilibration.
Thank you in advance for your great help!
Yu