WPI APOLLO 4000, Инструкция по эксплуатации

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APOLLO 4000
NITRIC OXIDE DETECTION
WORLD PRECISION INSTRUMENTS C-2
Calibration by the chemical generation of NO
(Type of NO sensor that can be calibrated with this method: ISONOP)
This method is recommended for use with the 2.0 mm sensor (ISO-NOP). However,
because it requires the use of strong acid it cannot be used with other NO sensors.
The first step is to prepare the following two solutions:
Solution #1:
0.1 M H
2
SO
4
+ 0.1 M KI
To make 500 mL of solution requires:
4.9 g of H
2
SO
4
(2.7 mL of concentrated H
2
SO
4
{18.4 M})
8.3 g of KI
Slowly add the sulfuric acid to about 400 mL of distilled water while stirring. Then
add the KI and mix; finally add distilled water to a final volume of 500 mL.
Solution #2:
50
µ
M KNO
2
(or NaNO
2
)
The recommended method for preparing this solution is to purchase an ion
chromatography liquid nitrite standard (NaNO
2
or KNO
2
) which may be diluted as
appropriate. Standard Nitrite is available from WPI, catalog #7357.
Alternatively, crystalline reagent KNO
2
may be used, but the user should note that
KNO
2
is extremely hygroscopic and degrades once exposed to atmospheric
moisture. It is therefore recommended that if the crystalline reagent is to be used
that the reagent packaged under argon be purchased (available from Eastman
Kodak Chem #105 7462), and that it be stored in a desiccator. While this will
extend the life of the reagent, it will need to be replaced more frequently than will
the liquid standard. The standard nitrite solution prepared from this compound
should be stored in a gas-tight bottle and refrigerated.
This method of calibration is based on the following reaction:
2KNO
2
+ 2KI + 2H
2
SO
4
→
2NO + I
2
+ 2H
2
O + 2K
2
SO
4
(1)
where a known amount of KNO
2
is added to produce a known amount of NO. The
quantity (and so the concentration) of NO generated can be calculated directly
from the stoichiometry if the concentrations of the reactants are known. Since KI
and H
2
SO
4
are present in great excess the limiting reagent is KNO
2
. Experiments