Dear all,

I got into trouble with LC-MS/MS quantitation in MRM mode. I do not know what I should call the phenomenon.

The preliminary mass transitions used for the analyte of interest and its internal standard is as follows: 340 > 239 (high-intensity ion), 340 > 194 (medium-intensity ion), 340 > 195 (low-intensity ion) and 237 > 194 (internal standard). When I used this condition, I got the good result regarding intensity and peak shape.

However, when I removed the medium-intensity and low-intensity transitions, I got a low intensity and poor peak shape of the internal standard even though I used the same analytical condition and same sample.

I have rechecked the phenomenon many times and I got the same result.
Hopefully, I could get some valuable advice on this issue from all of you.

Many thanks.