Calibration
Equipment Required
Thermo Fisher Scientific
Model 42
i
Trace Level Instruction Manual
4-5
Use the NIST traceable NO standard and the GPT calibration procedure
to calibrate the NO, NO
x
, and NO
2
responses of the instrument. Also
determine the converter efficiency of the analyzer. Refer to the calibration
procedure in this manual and in the Code of Federal Regulations, Title 40,
Part 50, Appendix F for exact details.
Note
Ignore the recommended zero offset adjustments.
▲
Use the following procedure to calculate the NO concentration standard
and NO
2
impurity.
1.
Generate several NO concentrations by dilution of the NO working
standard.
2.
Use the nominal NO concentration, [NO]
NOM
, to calculate the diluted
concentrations.
3.
Plot the analyzer NO response (in ppm) versus the nominal diluted
NO concentration and determine the slope, S
NOM
.
4.
Calculate the [NO] concentration of the working standard, [NO]
STD
,
from:
S
x
]
[NO
=
]
[NO
NOM
NOM
STD
5.
If the nominal NO concentration of the working standard is unknown,
generate several NO concentrations to give on-scale NO responses.
6.
Measure and record F
NO
and F
T
for each NO concentration generated.
7.
Plot the analyzer NO response versus F
NO
/F
T
and determine the slope
which gives [NO]
STD
directly. The analyzer NO
x
responses to the
generated NO concentrations reflect any NO
2
impurity in the NO
working standard.
8.
Plot the difference between the analyzer NO
x
and NO responses versus
F
NO
/F
T
. The slope of this plot is [NO
2
]
IMP
.
Assaying a Working NO
Standard Against a NIST-
traceable NO Standard