Acidic gases are important trace components of the troposphere because they contribute to particle formation and acid deposition. Here, a mist chamber (MIST) was used to collect acidic gases into aqueous solutions, which were analyzed by ion chromatography (IC) or capillary electrophoresis (CE). A CE method was developed, in which anions were separated in either a didodecyldimethylammonium or dimethyldioctadecylammonium bromide modified capillary at pH 5.86 and detected by indirect UV absorbance using naphthalenedisulfonate as probe with detection limits of 10 to 20 µM. The MIST collection efficiency (COE) was determined by chemical ionization mass spectrometry using acetate reagent ion. For HCOOH, the COE was < 80% when deionized water was used as trapping solution. The mass spectrometer was calibrated by MIST – IC and was superior with respect to response time (1 s versus 10 min), detection limit (< 100 ppt versus ~6 ppb), and near-absence of inlet memory effects.