The use of a custom mode electron capture detector to determine mixing ratios of environmental tracers: Sulfur hexafluoride, chlorotrifluoromethane and bromotrifluoromethane

► Resonance mode of ECD operation was optimized for detection of CF3Cl and CF3Br. ► 50-fold amplification of the ECD signal was obtained for CF3Cl. ► 3.5-fold amplification of the ECD signal was obtained for CF3Br. ► Activation energies of CF3Cl and CF3Br were determined.