Asakawa highlighted the impact of the capillary interface (capillary-skimmer vs. capillary-RF Lens) of an ESI-triple quadrupole tandem mass spectrometer ) With a capillary-skimmer interface, the internal energy distributions of ions are much lower and narrower (blue curve in Figure ) than with the capillary-RF lens interfaces (yellow and red curves in Figure ). The effect is huge: the average internal energy can vary by a factor of two. In addition, the gas throughput into the first vacuum stage also influences the internal energy distribution of the ions . The density of molecules and atoms, present in ion transfer/focusing electrodes in the first vacuum stage, increased with the gas throughput.