D
ET
innovations in chemical detection
TANOEM TID:
2
SIMULTANEOUSSIGNALS, many signal combinations arepossible
ELECTROMETER 2
Many different tandem signal combinations are
possible, depending on the type of thermionic
sources/FID probe used and the composition of
detector gases supplied. Some possibilities are as
follows:
TID-1-N
2/HWCID
- simultaneous detection of oxygen–
ates and hydrocarbons in gasolines;
TID-1-Air/NPD - simultaneous detection of organochlo–
rine and nitrogen/phosphorus pesticides;
FID/FTID-2 - simultaneous detection of hydrocarbons
and high concentration halogenates;
Response:
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GAS EXIT
•
•
L - GAS 1
&
GC
EPFLUENT
Each stage requires a thermionic source or FlOprobe,
and their separate heating current and polarization
electronics. The simultaneous signals from the two
stages require two negative ion electrometers for
measurement.
THERMIONIC
SOURce 1
In a TANDEM TID, two independently controlled
thermionic ionization detection stages are combined in
a series configuration. The first stage is a MODIFIED
TID/FID tower (Varian GC models) or a MODIFIED
REMOTE FID tower (Agilent 6890 and HP 5890 GC
models) that mounts onto the existing FlO base on the
GC. The second stage is a TID TRANSDUCER that
attaches to the exit port of the first stage. Two
different detector gases can be supplied through the
lines in the detector base which normally supply "H
2 "
and "air" to an FlO. A third gas inlet in the modified
first stage tower provides an additional detector gas
flow between the two stages. The two detection
stages can be easily decoupled to allow separate
operation of each structure. The f irst detection stage
can be purchased separately, and the second stage
may be added later as needed.
Equipment:
DETector Engineering
&
Technology, inc.
