Calibration
Equipment Required
4-6
Model 42
i
Trace Level Instruction Manual
Thermo Fisher Scientific
A source of zero air free of contaminants should be used as described earlier
in this chapter. Contaminants can cause a detectable response on the
instrument and may also react with the NO, O
3
, or NO
2
during the gas
phase titration.
Use the following definitions for the remainder of this chapter.
P
R
=
Dynamic parameter specification to ensure complete reaction of the
available O
3
, ppm-min
[NO]
RC
=
NO concentration in the reaction chamber, ppm
t
R
=
residence time of the reactant gases in the reaction chamber, min
[NO]
STD
=
Concentration of the undiluted NO standard, ppm
F
NO
=
NO flow rate, sccm
F
O
=
O
3
generator air flow rate, sccm
V
RC
=
Volume of the reaction chamber, cc
F
T
=
Analyzer demand plus 10 to 50% excess
The O
3
generator (ozonator) airflow rate and the NO flow rate must be
adjusted such that the following relationships hold:
min
-
ppm
2.75
t
x
]
[NO
=
P
R
RC
R
≥
)
F
+
F
(
F
]
[NO
=
]
[NO
NO
O
NO
STD
RC
min
2
<
F
+
F
V
=
t
NO
O
RC
R
Use the following procedure to determine the flow conditions to be used in
the GPT system.
1.
Determine F
T
, the total flow required at the output manifold, which
should be equal to the analyzer demand plus 10 to 50 percent excess.
2.
Establish [NO]
OUT
as the highest NO concentration that will be
required at the output manifold. [NO]
OUT
should be about equal to
Zero Air
Dynamic Parameter
Specifications for
Gas Titrator
Determining GPT System
Flow Conditions
