The document discusses several methods for the detection and determination of carbon monoxide (CO), nitrogen oxides (NO and NO2), and carbon dioxide (CO2). It describes the chemiluminescence method for measuring NO using the reaction of NO with ozone to emit light, and the infrared absorption and ultraviolet absorption methods for measuring NO, NO2, and other gases. It also discusses determining CO using non-dispersive infrared analysis, resonance fluorescence, chemical absorption with cuprous salts, catalytic combustion on platinum, and various redox reactions.

1. Prepared BY:
Ishfaq Ahmad
Topic:
CO,CO2 ,NO and NO2 Detection and
determination
Determination Nitrogen oxides and CO
Environmental measurement is accomplished in many
ways. Air samples may be collected using sample bags or
containers and analysed using gas chromatography. Air Quality

2. Monitoring International accords such as the Montreal protocol,
or Kyoto accords call on all industry everywhere to monitor,
control and reduce their emissions before discharging them into
the environment. There are a number of different particulate and
gaseous emissions which result from smoke stack emissions in
many industries including manufacturing, chemical and
petrochemical, and power generation.
1. Chemiluminescence method NO
The chemiluminescence reaction which occurs with NO
and ozone is used to measure the concentration of NO. The NO
in the sample gas and the O3 produced from air using silent
discharge or the radiation of ultraviolet rays are mixed with each
other in the reaction cell. A part of the mixed gas becomes
NO2 (NO2*) in the excited state. When this NO2* returns to the
normal state, it emits light. The intensity of this light is measured
with a silicon photodiode or a photomultiplier to obtain the
concentration of NO.
To measure nitrogen dioxide NO2
(a) The sample gas is passed through a converter filled with
reducing catalyst and the concentration of nitrogen oxides is
measured; and
(b) This concentration is deducted by the value (for nitrogen
monoxide) obtained without using the converter. The gas which
has l eft the reactor still contains corrosive
ozone. Therefore, this ozone is eliminated using adsorption or
thermal decomposition before the gas is exhausted.
This method features a high sensitivity, a broad dynamic range, a
fast response, and measurements free from any interference other
than CO2. The effect of CO2 varies depending on the structure of
the reactor, the ratio of gas flow rates, and the internal pressure.
If these factors are assumed to be constant, the effect is
dependent on the concentration of CO2 and the reading of NO is
affected accordingly. This means that when the concentration of

3. CO2 remains stable, the interference of CO2 is eliminated from
the reading of NO by electrically compensating for that value.
The converter which converts nitrogen dioxide into nitrogen
monoxide has a limited service life, requiring periodical
replacements and checks of its conversion efficiency.
2. Infrared absorption method
The changes in the volume of infrared rays in the
neighborhood of 5.3 micro-m absorbed by NO are measured
using a selectivity detector, and then the concentration of NO is
obtained. The principle used for this method is the same as that
for the analyzers for SO2, CO, and CO2. NO2 is not directly
measured, but first reduced to NO through a reducing type
converter and then measured as NO and NO2 .This method is less
affected by the flow rate of the sample gas and makes the daily
maintenance of control of the relevant analyzer easier.
It is, however, affected by the interference of moisture and
CO2 contained in the sample gas. The countermeasures against
this interference include using a gas filter filled with gases of the
interference components, an optical solid filter which selects only
the wavelength band absorbed by NO, or a compensatory
detector which compensates for the effect by obtaining the
signals for the interference components.
3. Ultraviolet absorption method
In this method, the concentration of NO or NO2 is obtained
by measuring the changes in the volume of ultraviolet rays in the
range from 195 to 230 nm absorbed by NO or in the range from
350 to 450 nm absorbed by NO2. To measure the concentrations
of NO and NO2 as the concentration of NOx, there are two
methods available. One is to individually measure the
concentrations of NO and NO2 and then add the measured values.
The other is to pass the sample gas through an oxidation type
converter to convert NO into NO2 and then measure the

4. concentration of NOx as that of NO2.
As can be seen from the absorption spectrum in Fig.4.2.4, this
method is not affected by CO, CO2, water, and ammonia which
coexist in the exhaust gas because these substances are not
absorbed. Since NO2 is measured using wavelength of around
400 nm, the wavelength range of ultraviolet rays absorbed by
SO2 can be avoided.
Absorption spectrum of NO, NO2
4. Potentiostatic electrolysis method
The NO and NO2 which have been dispersed and then
absorbed in electrolyte through a gas-permeable diaphragm are
electrochemically oxidized on an electrode which is maintained
at a constant potential. The electrolytic current generated during
this oxidation is used to continuously measure the concentration
of NOx in the sample gas. The analyzer using this method can be
designed to be smaller and lighter, making itself suitable for
portable use. When a large amount of NO2 is contained in the
sample gas, the detection sensitivity of the analyzer becomes
1:0.9 in a ratio of NO to NO2. Therefore, NO2 is converted into
NO using a reducing type converter and then the concentration of
NO is measured as that of NO. Since the interference of SO2 and

5. H2S is large, there is another method available, in which the
measurement is performed after this interference is eliminated
with an SO2 scrubber. The electrode has a limited service life,
requiring periodical replacements.
Determination of CO
Chromatography (GC)
Carbon monoxide (CO) from industrial processes and
incomplete combustion of wood, oil, gas and coal. Carbon
dioxide (CO2), Sulphur Dioxide (SO2), and Nitric oxides (NO
and NO2) from combustion of gas, oil and coal. Hydrogen
sulfide (H2S) and methyl mercaptan (CH3SH) from pulp and
paper mills. Hydrocarbons resulting from incomplete combustion
of fuels. Requirements for vehicle exhaust emission levels for
carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons and
oxygen (O2).In all areas, a variety of environmental pure gases
and calibration of gas standards are required.
Non-dispersive Infrared Analyser
For carbon monoxide detection we use a non dispersive
infrared analyser which is made up of following components;
 IR radiation sources
 Sensing cell
 demodulator amplifier
 reference cell
 sample Cell

6.  chopper
Sample cell in which a sample of air is kept having reference
sample the IR beam from source is reflected by a chopper
through the sample and reference cell. intensity of radiation
decreased when the carbon monoxide absorb some radiation. The
carbon monoxide detector absorb radiation and become hot in the
portion of detector in front of sample sale receiving lower
intensity and becoming less hot. Third eye from more from low
temperature quotient the high temperature foshan the distance of
diaphragm is proportional to the intensity difference of IR
radiation which is entered proportional to the concentration of
carbon mono oxide.
Advantages
 Not sensitive flow rate
 Required dry sample
 They are independent at air temperature changes
 Sensitive to wide concentration range
 The system is easy to use.
Resonance fluorescence
Carbon monoxide in a vacuum ultraviolet has been used in
hyper the high sensitive instrument. In this technique
atmospheric carbon balance monoxide absorb radiation in the
range of 150nm from radio frequency discharge lamp and
fluorescence from excited carbon monoxide is detected by
photomultiplier tube PMT. Lamp generate Plasma in a
continuous flow of carbon dioxide in argon. the pressure in the
fluorescence chamber must be maintained between 7 and 9 bar to
balance interference from Oxygen and Carbon mono oxide

7. signals. Permeation tube can also be used for preparing standard
mixture of such pollutant gases as Sulphur dioxide and Nitrogen
dioxide.
Determination of carbon monoxide by chemical absorption
cuprous salt solution are the most frequently used
volumetric absorption reagent for determination of CO in various
mixture reagent used are acid cuprous chloride, ammonical
cuprous chloride, beta-naphthol suspension in acid cuprous
sulphate cuprous chloride reagents rapidly absorb CO with the
formation of Cu2.Cl2.2CO.4H2O. An unstable molecular
Complex that reversibly decomposed in partly saturated reagent
unless certain partial pressure of unabsorbed carbon monoxide is
present in the residual gas above the solution. Fresh cuprous
chloride absorb almost all carbon monoxide but for the remaining
carbon monoxide we use two pipette. Some of carbon monoxide
detected by one pipet it and other remaining treaces are detected
by the other.
Beta naphthol absorbs carbon monoxide slowly
incompletely until saturated with the formation of stable
molecular complex. It is useful for low concentration
determination. Carbon monoxide absorbs in acid cuprous
chloride and beta naphthol acid cuprous sulphate mixture in
pippete. Most of the carbon monoxide absorbs in one and other
traces in other pipette. Cuprous chloride is a solution of 100
grams in 600 ml. Of concentrated hydrochloric acid solution is
stored in contact with Spiral of copper wire for some days it is
reduced to colourless cuprous condition does ready to use
inactive reagent maybe prepared by reduction absolution with
25% solution of stannous chloride in 1: 1 hydrochloric acid until

8. yellow reagent is obtained this reagent is useful for carbon
monoxide in gaseous mixture.
Ammonical cuprous chloride is a solution of 135 grams of
cuprous chloride in 150 grams of Ammonium Chloride in 500 ml
water. Before use it is reduced to colorless with metallic copper
in dilute with one third of its volume up concentration
Ammonium hydroxide before use. Brockner and Grobner
prepared neutral cuprous chloride by which carbon monoxide is
observed completely absorption capacity is 50% it is prepared by
dissolving 125 grams of cuprous chloride and 265 gram of
ammonium Chloride in 750 ml of water reduction with metallic
copper colorless reagent is ready to use.
Determination of carbonmomoxide by slow combustion on a
heated Platinum filament
CO may be determined by burning in air which Platinum
wire filament that is heated to bright yellow. This method is
called slow combustion method. Carbon monoxide is oxidized to
carbon dioxide. By measuring the volume contraction by burning
volume of carbon dioxide formed carbon monoxide present may
be determined by the formula .
CO=23(contraction + CO2)
For CO and H2 , CO =CO2
Hydrogen = 2/3 (contraction - carbon dioxide)
For CO and CH4
CH4 = 2/3 (contraction - CO2)

9. So CO= CO2 - CH4
Following formula is applied for calculation of three constituents
H2 = contraction - oxygen consumed
This technique is very sensitive,precise and accurate the result
object method was 99.9% accurate (Branham and Shepherd)
Carbon monoxide determination buy catalytic combustion in
air are Oxygen on platinized Silica Gel
In the presence of excess air and oxygen, carbon
monoxide, hydrogen and mehane can be oxidize catalytically and
platinised silica Gel, heated with control temperature furnace.
Calculation is similar to that of slow combustion method. It
reported that silica Gel with 0.125 percent platinum can oxidizes
hydrogen at 200 0C, carbon monoxide at 200 0C , methane at 500
0C, ethane at 165 0C, and propane at 150 0C carbon monoxide is
poisonous at 210 0C. Platinised Silica Gel tube is used with
different Orsat apparatus to determine paraffin. After removal all
the extra gases at 300 0C carbon monoxide can be determined by
passing the residual gases through a platinised silica at 500 0C.
Explosion may occur during experiment so protection and safety
must be required.
Carbon monoxide determination by Redox reactions
Carbon monoxide is readily oxidized to carbon dioxide by
variety of reagents most commonly used method is solid state
reduction method.
Solid state reagent

10. Various Platinum group metal and heavy metal used to
oxidize or catalyzed oxidation carbon monoxide in presence of
excess air.
The reaction involve
CO+metal oxide  metal +CO2
CO+ 12 O2 CO2 + 68kcal
It can be based on direct measurement of either thermal
increment in the oxidant mass resulting from heat of oxidation
are carbon dioxide formed. When concentration is low is pirated
through Hopcalite catalyst or silver permanganate zinc oxide is
used to oxidize ultimately thermal reaction takes place the heat
produced is proportional to carbon monoxide concentration. The
thermal effect can be measured by Thermocouple, thermopile,
thermistor or thermometer.
In general all solid state oxidants, and all ranges of carbon
monoxide concentration in a mixture by measure CO2. When
concentration is high then it is measured by gas volumetric
absorption or by gravimetric method. When concentration is low
then it oxidized to form small amount of carbon dioxide,
absorbed in dilute alkali solution and determined by electrical
conductivity or by acidimetric titration. Hopcalite is a granular
mixture of manganese dioxide and cupric oxide, which is capable

11. of catalyzing the oxidation of carbon monoxide with the
concentration at room temperature. The reaction is temperature
dependent moister. Hydrogen sulphide and hydrogen cyanide
poison its activity drying agent used to remove these effects.
Thermal effect of the oxidation is measured moisture promotes
the oxidation which is both catalytic and stoichiometric, and
silver permanganate is consumed .
Oxidant reagent solution
Most of colorimetric method use palladous salt, which is
reduced itself and gives black metallic palladium.
The reaction is given as
CO+PlCl2+H2O -----Pl0 +HCl+CO2 "Lamb and Larson" .