1. The problem statement, all variables and given/known data There are four scan modes for tandem MS: Product ion, Precursor ion, Neutral loss scan mode and MRM. e.g. In MRM, the result of graph is Intensity versus time, but NOT versus m/z. What does the "time" in the graph refers to? 2. Relevant equations 3. The attempt at a solution For MRM, ions are selected in MS1 and fragmented in collision cell. The daughter ions then selected in MS2 and go to the detector. The result of graph should be intensity versus m/z. But it is against time. Does it means it the selected m/z in MS2 undergo LC after that? Or the time is the detection time?