Thermo Scientific 42iQLS, Instruction Manual

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Calibration
Equipment Required
4-2 42iQLS Instruction Manual Thermo Scientific
The quantitative nature of this reaction is such that when the NO
concentration is known, the concentration of NO
2
can be determined.
Ozone is added to excess NO in a dynamic calibration system, and the NO
channel of the chemiluminescence NO-NO
2
-NO
x
analyzer is used as an
indicator of changes in NO concentration.
When O
3
is added, the decrease in NO concentration observed on the
calibrated NO channel is equivalent to the concentration of NO
2
produced. Adding variable amounts of O
3
from a stable O
3
generator can
change the amount of NO
2
generated.
The following equipment is required to calibrate the analyzer:
●
Zero gas generator
●
Gas phase titrator
A zero air source, such as a Thermo Scientific 111iQ Zero Air Supply , free
of contaminants such as NO, NO
2
, and O
3
is required for dilution,
calibration, and gas phase titration.
The zero air source should be at an elevated pressure to allow accurate and
reproducible flow control and to aid in subsequent operations such as
drying, oxidation, and scrubbing. An air compressor that gives an output of
10 psig is usually sufficient for most applications.
Several drying methods are available. Passing the compressed air through a
bed of silica gel, using a heatless air dryer, or removing water vapor with a
permeation dryer, are three possible approaches.
NO is usually oxidized to NO
2
in order to ease its scrubbing. Oxidation
can be accomplished by either ozonation or chemical contact. During
ozonation, the air is passed through an ozone generator. The O
3
that is
produced reacts with the NO to form NO
2
. Care must be taken to allow
sufficient residence time for the ozonation reaction to go to completion.
Chemical oxidation is accomplished by passing the air stream through a
reacting bed. Such agents as CrO
3
on an alumina support or Purafil® are
very efficient at oxidizing NO to NO
2
. The chemical contact approach has
the advantage of needing no electrical power input for its application.
O
+
NO
O + NO
2 2
3

Equipment Required
Zero Gas Generator
Compression
Drying
Oxidation