• •
•
Thermionic Surface Ionization
Unique GC detection technology converts selected chemical
compounds into measurable ion currents using a family of
electrically-heated, catalytically-active ionizing surfacesmade
of proprietary ceramic materials.
Optimumconcentriccylinderdetectorgeometryusedon theAgilent6890/7890NPDand
all DET hardware features a cylindrically-shaped ion source positioned on the axis of
an ion collector cylinder, with top access for easy interchange of ion source types.
4 parameters determine selectivity
THERMIONIC IONIZATION DETECTOR DESIGN
(CONCENTRIC CYLINDERGEOMETRY)
and sensitivity:
1. catalytic ionizing activity of the ion
source as determined by the
Ceramic
Ion Source
composition of its ceramic coating
(1/16
in. dia.)
(an unlimited number of ceramic
formulations are possible);
ture of the ion source
the range
300 • 900°C);
I
tion of the gases flowing
past the ion source (e.g., N
2 ,
Air, O
2 ,
I
I
N
2
0 ,
H
2 ,
and combinations thereof);
I
I
I
r
!~:
Sample Inlet
Gas 2
J
:
L
Gas
2
I
(Air,
N 2)
4. the magnitude of the polarizing
r
I
L
Sample & Gas
1
&
Makeup (Gas
3)
voltage between the ion source and
(H 2, N 2,
Air)
collector (typical ranqe - 4 to • 100 V).
Multiplemodes of detection are achieved using the same basic equipment, achoice of
different ion sourceceramics, and various permutationsof the
4
operating parameters
detector selectivity choices include compounds containing N, P,
0,
CI, Br, I, Pb, Sn, or
Si atoms, or
N0
2 ,
Pyrrole, CH
2 ,
and certain other functional groups - new compound
selectivitiescontinue tobe identified, aswell asmanytandem combinationsofdifferent
detection modes.
Inexpensive equipment based on Thermionic Surface Ionization principles
provides detection capabilities unmatched by any other type of GC detector.
D
E
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