I am trying to validate acrylamide analysis in LC-MS/MS but I can see arylamide at first and second injections after then I could not detect any peak. I am using C18 column and 99.5:0.5 (water:MeOH) mobile phase and 0.1%formic acid in 50%-50% (asetonitril-MeOH) for postwashing.
Mrs/Miss. Akgün,
There is a lack of problems at a level instrucmental features. So remains, error contribution to the data from the operator(s).
Conventional C18 columns will not handle 99.5% water. By running that much water you cause what is known as phase collapse, which is a condition under which your column quits working. It takes a very long time for the column to recover from this condition. You need to move to a much more polar phase ("aqueous" phases or fluoropropyl phases) or possibly try HILIC. Here is a reference that you can read:
https://az621941.vo.msecnd.net/documents/215cc3c5-6614-4dab-94b3-177a3d1746f4.pdf
If your response is linearly decreasing with time then your sample might be degrading. Change diluent in which sample are prepared.
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