Abstract
Gas-phase hydrogen/deuterium (H/D) exchange between D2O, CH3OD, CH3CH2OD, ND3 and ascorbic acid was examined, in an attempt to understand the mechanism responsible for the gas-phase ion/molecular reactions that occur in Direct Analysis in Real Time (DART)．Ionized water/ammonium clusters played an important role in the H/D exchange process, known as a transient microenvironment (TME)．Argon was used as an alternative DART gas to eliminate formation of ionized water clusters. These experiments clearly characterized the gas-phase H/D exchange process of positive-ion DART.
