Thermo Fisher Scientific
Model 42
i
Trace Level Instruction Manual
4-1
Chapter 4
Calibration
This chapter describes procedures for performing a multipoint calibration
of the Model 42
i
Trace Level. The information described here is considered
be adequate to perform the calibration. However, if greater detail is desired,
the user is referred to the Code of Federal Regulations, Title 40, Part 50,
Appendix F.
The calibration technique is based on the rapid gas phase reaction between
NO and O
3
which produces stoichiometric quantities of NO
2
in
accordance with the reaction:
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 sections discuss the
required apparatus and procedures for calibrating the instrument:
●
“
Equipment Required
” on page
4-1
●
“
Pre-Calibration
” on page
4-8
●
“
Calibration
” on page
4-9
●
“
Calibration in Dual Range and Auto Range Mode
” on page
4-16
●
“
Zero and Span Check
” on page
4-20
The following equipment is required to calibrate the analyzer:
ν
h
+
O
+
NO
O
+
NO
2
2
3
→
Equipment Required
