Comment on egusphere-2025-5685

Abstract. We have developed and characterized the performance of a portable time of flight chemical ionization mass spectrometer (Portable-TOF-CIMS) capable of detecting trace gases at parts per trillion by volume (pptv) mixing ratios in ambient air. The instrument is compact (0.063 m3), weighs less than 30 kg, and operates on 270 W of 24 VDC power. These characteristics allow it to be readily deployed on a range of mobile or stationary platforms with little electrical or structural engineering considerations. The mass spectrometer achieves a mass resolving power of (m/Δm) at mass-to-charge of 381 (m/Q) and a mass accuracy of < 10 ppm. The instrument can operate in both positive or negative polarity and therefore can detect a suite of different analytes depending upon the reagent ion chemistry. We demonstrate the instrument response to inorganic and organic trace gases using Iodide anion adduct and Benzene cation reagent ion chemistries and illustrate its performance sampling ambient air during a multi-week stationary deployment and mobile deployments from two different personal automobiles and from a cargo e-bike using only a battery to power the instrument during operation.