I am trying to expand the linearity of my method. There is in-source saturation (detector saturation is excluded by using isotopologues that did not improve linearity). However, at a certain retention time, where two of my analytes elute, there is a flat curve for one of the analytes but a perfectly linear curve for the other.
If there is an ionisation saturation in the source at a specific retention time, how is it possible that ions still can be formed in the source linearily for another analyte?
The two analyes are actually the same compound but a different transition is monitored.
Dear Asal Asali,
without having more detailed information about the equipment that you use, the analytes you want to detect, my first reaction would be mass specific detector overload. If you have co-eluting analytes which share some common mz values, they may get saturated, whereas some analyte specific mz/ values still show a perfect dose response reaction.
But to pinpoint the cause, I need more information about your experiment.
kind regards, Harrie Verhoeven
@Harrie A Verhoeven, excuse my late reply upon your quick response.
The analyte I am monitoring is M-glucuronide (MG). When I monitor the transition MG -> M, there is a saturation of the signal observed in the higher concentration calibration standards. However, when I monitor the M->X while injecting MG, I have a perfectly linear calibration curve. The M->X transition is actually the in-source fragmentation of MG, where the glucuronide moeity splits from the M. This makes me think of MS^3, but with a simple quadruple ms.