James_Ball wrote:
Unless doing MRM turn the collision and quench gas off, you will get much better sensitivity. Those are only needed for the fragmentation in the collision cell.
Thanks James. I still do not have answers why the instrument performed the EPA 525 method well for almost 2 years, until mid October 2017. I am running a curve today in EI (no EIEX) mode, with He@2.25, N2@0.5 (as I have run it in the past), cycloliner, splitless for 1.25 min at 300C. I have 2 methods setup, one 1uL injection, and the other one 0.5uL. I will report tomorrow. I am also thinking about creating MRM method for the problem compounds like metribuzin, butachlor, adipate, phthalate and methoxychlor to check. So you don’t have to read the entire thread - curve for the above mentioned compounds is convex (or concave up) and therefore the linear fit will not pass. I have made the curves so many times and in different ways. I would like to think that I am not the problem re: the curve prep.
I also ordered some new source parts to see if the cleaning had anything to do with it (just a reminder: the source was cleaned 3 times since early October, once during the annual PM by Agilent, second cleaning was done a different Agilent engineer about a week later, and the third cleaning by me few weeks ago).