In this work, we have shown that the detection sensitivity (or limit of detection) of a new Atmospheric Pressure-interface Time-of-Flight Mass Spectrometer (API-TOF-MS) is in the parts per quintillion (i.e., 10−3 parts per quadrillion, ppq; which is ∼ 30 ions cm−3) range with temporal resolutions of 1 s. When increasing the temporal resolution up to 1 min, the detection sensitivity could be reduced to the 10 parts per sextillion (i.e., 10−5 ppq; which is ∼ 0.3 ions cm−3) range, enabling the system to measure gaseous ions of extremely low concentrations. We also show that the mass spectrometer has a transmission of up to 1 %, and a mass resolution of 23,000 for ionic masses of ca. 600 Da, while it can be used in ways to induce collision dissociation of the sampled ions by tuning the operating conditions of the Atmospheric-Pressure-interface stage.