TID – Thermionic Ionization Detector


  • Highly selective to nitro functional groups
  • Also responds to chlorinated phenols
  • Detects down to 1 ppb
  • Convenient bead design
  • Can be run gas-less in the field
TID – Thermionic Ionization Detector
TID Bead
Basic Model

The Thermionic Ionization Detector is similar in design to the FID and NPD. The electrically heated thermionic bead (TID bead) is positioned so that the column effluent contacts the hot bead surface.

Analyte molecules containing NO2 (nitro) functional groups such as TNT (trinitrotoluene) undergo a catalytic surface chemical reaction. The resulting ions are attracted to a collector electrode, amplified, and output to the data system.

The TID is extremely selective, having little or no response to most aromatic and aliphatic hydrocarbons. The TID also responds to chlorinated phenols such as pentachlorophenol (PCP) at slightly less sensitivity.

For best sensitivity, the TID requires air for operation. If air is used as the carrier gas, no other detector gases are required. An air makeup gas is provided so that nitrogen or another gas can be used as a carrier. The TID can also be operated in a nitrogen-only environment with similar but not identical response characteristics.

The TID is featured on our explosives GC, which was tested by the EPA’s Environmental Technologies Verification (ETV) program for measuring explosives in soil.

8690-0017 TID detector