DART is an ambient MS ionization technique developed by JEOL . The ionization process is divided into two steps (Figure ). The gas plasma is formed where the gas (helium, argon or nitrogen) enters a discharge chamber and comes into contact with a discharge needle (typically 1-5 kV). Then, the hot plasma gas is transferred to the ion source where it interacts with the sample and transfers its charges to the analyte molecules. Several ionization processes can occur in the DART source, such as Penning ionization, proton transfer or charge transfer .