Hi to all,
I'm experiencing a too weird fact. I was studying how the matrix of my sample affected ylthe instrumental response of my analyte in LC MS. I use an esi detector, a c18 column. My analyte elutes at more than 10 minutes and the LC method is a gradient. Moreover, i divert LC flow to the waste for the first 10 minutes of the run to prevent MS source contamination from salts and other unwonted analytes. Mobile phases are methanol and water with me oh and ch3coonh4, with pH adjusted with formic acid.
The odd fact is that analyzing the analytes of interest dissolved in water, i have an instrumental response that is 100 fold lower compared to the response of this analyte when is in the final matrix that is NaCl+water.
Why I observe this? How does NaCl affect the instrumental response of the analyte? How is it possible if the analyte elutes too far from the "salt"elution region that is at the beginning of the run? I have excluded the first 10 minutes of the run from MS.
Moreover, I observe this increment only in MS, and not in UV. so it is not a reaction of my analyte with NaCl, but a matrix effect.
Do you have ever observed this? Have you some experiences, or literature to share?
Thank you