Seek help! Why the cardiolipin response measured by Agilent 6495C QQQ is so low?

I measured the TIC response of the same concentration (50 μM) of phosphatidylcholine (PC 14:0/14:0 MW≈677) in the same MS parameter, MRM mode, up to E8. However, the response of cardiolipin (CL (14:0)4 MW≈1240) is only E4. Among them, the ion pairs selected by PC and CL are also the most responsive. PC selection is [M + HCOO] - and [14:0 FA - H] -, and CL choose [M - H] - and [14:0 FA - H] -.

  • Hi Xinyu, 

    You are comparing the results E4 against what system? The same from the past or another system (from Agilent or another vendor)?

    If another system, did you perform the Optimizer of the source and collision cell parameters?

    Prior to any injections, I always perform a matrix blank injection in MS2 scan (from the min m/z to 3000 m/z) to make sure I do not have any contamination. Please do so as presence of PEG's or other contaminants will lower your signal drastically.

    Thank you

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