The flow injection-MS n analysis was performed by a Vanquish Duo UHPLC system coupled to an Orbitrap ID-X (Thermo Fisher Scientific) instrument. The instrument was calibrated in positive and negative ion mode with the Pierce™ FlexMix™ calibration solution prior to a library batch. Different setups were tested to extend the peak width for more MS n experiments, to reach the mass analyzer quickly, and to avoid sample carryover. Two pumps were connected with a T-piece. The first pump, that is, the delivery pump, ran through the autosampler. The flow for this pump was initially set to 45 µL/min for the injection to reach the T connection quickly. After 0.27 min the flow was decreased to 5 µL/min and kept constant until 1.35 min. Over the next 0.15 min, the flow was increased to 45 µL/min and kept constant for another 1.5 min to clean the sample lines and avoid sample carryover. The second pump, that is, the makeup pump, was used to broaden the elution profile. To always keep a combined constant flow of 55 µL/min, the makeup pump started with 10 µL/min, was increased to 50 µL/min after 0.27 min, and was constant until 1.35 min. The flow was gradually decreased back to 10 µL/min over the next 0.15 min and kept constant for another 1.5 min. The whole runtime per injection was 3 min. Both pumps used an isocratic mixture of 50:50 water:ACN, both with 0.1% FA. The switching of the flow speed is important for cleaning because the delivery pump runs with a low flow rate of 5 uL/min during most of the time of the sample delivery. It needs to be noted that the method can be also used with a second pump running constantly with 50 µL/min, resulting in an altered flow rate of up to 95 uL/min during the analysis but with no big changes during the data acquisition.