The droplets breakup and compounds ionization in the heated capillary were investigated; the ionization method was named Aerodynamic Thermal Breakup Droplet Ionization (ATBDI). The mass spectrometric analysis was performed for solutions of trinitrotoluene (TNT) in water, ethanol, and acetonitrile. Considering the total current and the target analyte peaks, the ionization efficiency in the heated capillary was correlated with the physical properties of the solvents. For aqueous and ethanol solutions of TNT, the limit of detection (LOD) was obtained when using the ATBDI mass spectrometry. It was estimated to be 10−7 g mL−1 and 10−6 g mL−1 for water and ethanol solutions, respectively.