multi EA 5000
Nitrogen analysis with the CLD 5000
43
7
Nitrogen analysis with the CLD 5000
7.1
Function and design
7.1.1
Function and measuring principle
Expansion of the basic module with the detection module allows the determination of
the nitrogen content in solids, liquids, and gases via chemiluminescence.
Organic nitrogen compounds can be determined as a TN sum parameter with the analy-
sis system. Inorganic nitrogen compounds are only detected if they can be digested in
the combustion furnace. Pure nitrogen cannot be analyzed.
The chemiluminescence of the reaction between nitrogen monoxide (NO) and ozone
(O
3
) is used for the determination. This reaction creates nitrogen dioxide in its excited
state (NO
2
*) for a short time. During the transition to the base state, the nitrogen diox-
ide emits electromagnetic radiation in the visible light spectrum. The light emitted is
proportional to the NO
2
* concentration. This allows measurement of the concentration
via light. NO is the only substance involved in the reaction, which means that this
method is very selective and not influenced by any other constituents of the measuring
gas.
NO + O
3
→ NO
2
* + O
2
NO* → NO
2
+ hv
The measuring gas is created during incineration of organic nitrogen compounds in the
basic module. It contains a mixture of NO and NO
2
, generally known as NO
x
.
R-N + O
2
→ NO
x
+ CO
2
+ H
2
O
R: Hydrocarbon residue, NO
x
: Mixture of NO and NO
2
The measuring gas is passed through a converter which renders the NO
2
portion usable
for the reaction and hence for detection purposes. The converter reduces NO
2
to NO.
The ozone required for the reaction is created in the device from the supplied oxygen
(O
2
). Excess O
3
is removed in the ozone decomposer after the reaction. The toxic gas is
not released into the ambient air.
7.1.2
Design
The detection module is used to determine the nitrogen content via chemiluminescence.
All components required for determination are mounted inside the sealed housing.
