The reactions of CF3O-, CF3O-H2O and CF3O-HF with HNO3, HCOOH, and CH3COOH have been studied at room temperature in a flowing afterglow instrument. Apart from the reaction of CF3O-HF with CH3COOH, all reactions proceed at the collision rate. Bare CF3O- ions react with the three acids mainly by fluoride transfer. An unambiguous identification of the reaction mechanisms of CF3O-H2O and CF3O-HF with the three neutral reactants is difficult to assess. The possibility to perform in situ measurements of HNO3, HCOOH, and CH3COOH concentrations in the atmosphere by chemical ionization mass spectrometry (CIMS), using a CF3O- ion source will be discussed.