Temperature-dependent sensitivity of iodide chemical ionization mass spectrometers

Abstract. Iodide chemical ionization mass spectrometry (CIMS) is a common analytical tool used in both laboratory and field experiments to measure large suite of atmospherically relevant compounds. Here, we describe systematic ion molecule reactor (IMR) temperature dependence iodide CIMS analyte sensitivity for wide range analytes experiments. Weakly bound clusters, such as HCl, HONO, HCOOH, HCN, phenol, 2-nitrophenol, acyl peroxynitrate (PAN) detected via the peroxy radical cluster, all exhibit strong IMR ranging from ?3.4 % ?C?1 5.9 (from 37 47 ?C). Strongly Br2, N2O5, ClNO2, PAN carboxylate anion, little no 0.2 ?0.9 The relationships weakly clusters provide an estimate net reaction enthalpy, comparison with database values indicates that these are thermal equilibrium. Ground site HCOOH data collected summer 2021 Pasadena (CA) corrected show reversal diel cycle, emphasizing importance this correction (35±6 during day, -26±2 at night). Finally, recommend two approaches minimize effect field, namely heating or cooling IMR; latter technique has added benefit improving absolute sensitivity.