A method is described for detecting and measuring trace amounts of pollutants of the group consisting of ozone, nitrogen dioxide, and carbon monoxide in a gaseous environment. A sample organic solid material that will undergo a chemical reaction with the test pollutant is exposed to the test environment and thereafter, when heated in the temperature range of 100-200 C., undergoes chemiluminescence that is measured and recorded as a function of concentration of the test pollutant. The chemiluminescence of the solid organic material is specific to the pollutant being tested

Conway, E. J.

Richards, R. R.

Rogowski, R. S.

English

NASA Technical Reports Server

' United States Patent [ I I I 3,977,83 1 
Fletcher et ai. [451 Aug. 31, 1976 
[541 METHOD FOR DETECTING POLLUTANT§ 
[ 761 Inventors: James C. Fletcher, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of; Robert S. Rogowski, 
Hampton, Va.; Ralph R. Richards, 
Greenville, Ill.; Edmund J. Conway, 
Newport News, Va. 
[22] Filed: Dec. 30, 1974 
[21] Appl. No.: 537,480 
1521 U.S. @I. ............................ 231232 E; 231230 R; 
231232 R 
Int. CI .* ................... GOlN 25/00; GOlN 27/62 
Field of Search ........ 231230 R, 230 PC, 232 R, 
231232 E, 254 
[51 ] 
[ 5 8 ]  
[561 References Cited 
UNITED STATES PATENTS 
3,528.779 911970 Foutijn .................................. 231230 
3,659,100 411972 Anderson et  al. ................ 231230 X 
3,749,929 711973 Wooten e t  al. ....................... 231232 
OTHER PUBLICATIONS 
Bowman et al., Science, vol. 154, 1966, pp. 
1454-1456, Ozone-Induced Chemiluminescence of 
Organic Compounds. 
Measurement of Atmospheric Ozone with the Chemi- 
16 
POWER 
PHOTOMULTIPLIER- 
n 
luminescent Method, Regener, J. of Geophysical Re- 
search, vol. 69, No. 18. 
Emisson Spectra from Mixtures of Atomic Nitrogen & 
Organic Substances, Kiess et al., 7th Symposium on 
Comb., London, Oxford, 1958. 
Chemiluminescent Material, Am. Cyanamid, Report 
No. 2, ARPA, No. 299, Amend D., Contract Nonr 
42000( 00). 
Primary Examiner-Morris 0. Wolk 
Assistant Examiner-Michael S .  Marcus 
Attorney, Agent, or Firm-Howard J. Osborn; Wallace 
J .  Nelson; John R. Manning 
[571 ABSTRACT 
A method for detecting and measuring trace amounts 
of pollutants of the group consisting of ozone, nitro- 
gen dioxide and carbon monoxide in a gaseous envi- 
ronment wherein a sample organic solid material that 
wil! undergo a chemical reaction with the test pollut- 
ant is exposed to the test environment and thereafter, 
when heated in the temperature range of 100"-200°C., 
undergoes chemiluminescence that is measured and 
recorded as a function of concentration of the test 
pollutant and wherein the chemiluminescence of the 
solid organic material is specific to the pollutant being 
tested. 
6 Claims, 3 Drawing Figures 
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3,977.83 1 
1 
METHOD FOR DETECTING POLLUTANTS 
ORIGIN OF THE DISCLOSURE 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 
85-568 (72 Stat. 435; 42 USC 2457). 
BACKGROUND OF THE INVENTION 
The present invention relates to a method for detect- 
ing and measuring trace amounts of various pollutants 
in a gaseous environment. In one aspect, the invention 
relates to a method for detecting and measuring ozone; 
in another aspect, to a method of detecting and mea- 
suring trace amounts of nitrogen dioxide and in a third 
aspect, to a method of detecting and measuring carbon 
monoxide. 
There are many known methods of determining the 
presence of trace impurities or pollutants in a gas. 
However, several of these methods require the use of 
devices that are cumbersome, expensive, or both, and 
there is a need for a simple and inexpensive reliable 
technique. This need is particularly acute in spacecraft 
and other installations where weight and bulkiness are 
of primary importance. 
Accordingly, it is an object of the present invention 
to provide a simple and reliable technique for detecting 
and measuring trace amounts of various pollutants in a 
gas. It is a further object to provide such a technique 
which utilizes thin sheets or layers of organic solid 
materials which undergo chemical changes in the pres- 
ence of selected pollutants and thereafter undergo 
chemiluminescence when heated. 
Another object of the present invention is to provide 
lightweight, inexpensive pollution detectors with de- 
layed readout capabilities. 
BRIEF SUMMARY OF THE INVENTION 
According to the present invention the foregoing and 
other objects are attainable by providing a thin layer of 
dry organic solid material that will undergo a chemical 
change in the presence of trace amounts of a specific 
pollutant in a gaseous environment and thereafter un- 
dergo chemiluminescence when heated. The total inte- 
grated light intensity measured during the heating cycle 
is a measure of the exposure to the concentration of the 
specific pollutant being tested. 
The dry sensitive solid organic material suitable for 
detecting trace quantities of ozone according to the 
present invention is selected from the group consisting 
of rubrene, poly( ethylene 2, 6-naphthalene dicarboxyl- 
ate) and 9,10 diphenyl anthracene. Organic solids that 
are specific for detecting trace amounts of nitrogen 
dioxide in a gaseous mixture are 3,5 diaminobenzoic 
acid and polyvinyl alcohol while the solid organic poly- 
vinyl pyrrolidone is specific for carbon monoxide. 
DETAILED DESCRIPTION 
A more complete appreciation of the invention and 
many of the inherent advantages thereof will be more 
clearly understood by reference to the following de- 
tailed descriution when considered in connection with 
2 
sion intensity from the exposed organic material ac- 
cording to the present invention, 
FIG. 2 illustrates the chemiluminescent spectra of 
ozonated and photo-oxidized rubrene, and 
5 FIG. 3 illustrates the chemiluminescent response 
curve for heated ozonated solid rubrene exposed to 
0.15 ppm ozone. 
Referring now to the drawings and mgre particularly 
to FIG. 1, there is shown the apparatus generally desig- 
10 nated by reference numeral 10 for detecting and mea- 
suring chemiluminescence according to the present 
invention. Apparatus 10 includes a housing 12 contain- 
ing a conventional photomultiplier tube 14 having yel- 
low response and in electrical connection with a suit- 
15 able power supply 16. A solid organic sample 18 that is 
to be measured for chemiluminescence is positioned in 
sample holder 20 adjacent heater element 21. Electric 
leads 22, 23 connect heater element 21 with a suitable 
power supply, not shown. A thermocouple 24 is in 
20 electrical connection with one of the pens on dual pen 
strip recorder 26 via lead wire 28. The other pen of 
recorder 26 is in eiectrical connection with an elec- 
trometer 30 via lead 31 to record the output received 
through lead 32 from photomultiplier 14. 
Housing 12 is provided with a pair of openings in the 
sidewall thereof as designated by reference numerals 
34 and 36 and shown closed, respectively, by covers 35 
and 37. The various components of apparatus 10 are 
conventional, commercially available items, for exam- 
30 ple, photomultiplier 14 may be an EM1 9558 photomul- 
tiplier (green-yellow response) available from Gencom 
Division, VARIAN/EMI, 80 Express Street, Plainview, 
New York 1 1803; electrometer 30 an Elcor integrating 
electrometer available from Elcor, Inc., Falls Church, 
35 Virginia, and dual pen recorder 26 is an Electronik 194 
from Honeywell, Inc., Fort Washington, PA 19034. 
Thermocouple 24 is a conventional chromel/alumel 
thermocouple soldered or otherwise thermally con- 
nected to sample holder 20 and electrically monitored 
40 by recorder 26 to continuously record the temperature 
of sample 18 as heated. When testing for ozone, sample 
18 will be a thin layer of material selected from the 
group consisting of rubrene, poly(ethy1ene 2,6 naptha- 
lene dicarboxylate) and 9,lO diphenyl anthracene. 
45 When testing for nitrogen dioxide the sample will be a 
thin layer of material selected from the group consist- 
ing of 3,s diaminobenzoic acid and polyvinyl alcohol 
and when testing for carbon monoxide the sample will 
be a thin layer of polyvinyl pyrrolidone. 
The operation of the device described above is now 
believed apparent. In one application of the invention, 
the sample 18 to be tested for chemiluminescence is 
placed in sample hoider 20 through one of the openings 
34, 36 and the container cover replaced to close the 
5 5  container. In this test, the sample 18 would have previ- 
ously been exposed to the test environment to permit 
the gas-solid reaction therewith. During exposure and 
testing of sample 18 care is exercised to prevent expo- 
sure of the sample to light to minimize reaction of the 
60 sample with oxygen in presence of ultraviolet radiation 
since some of the sample materials are known to pro- 
duce chemiluminescence when reacted with oxygen in 
the presence of light. 
The exposed solid sample 18 is heated to 
25 
50 
the specific' examples and accompanying drawings 65 100"-200°C. by heater element 21 and light emitted by 
wherein: chemiluminescence, is detected by photomultiplier 14, 
FIG. 1 is a schematic diagram of an apparatus useful amplified by electrometer 30 and recorded simulta- 
for measuring the integrated chemiluminescent emis- neously with the temperature on dual pen recorder 26. 
3,977-83 1 
3 
The light output from the sample rises to a maximum 
in a few seconds as shown in the graph of FIG. 2 for 
ozonated rubrene and then gradually decays to zero in 
approximately two minutes. 
The total integrated light intensity measured during 
the heating cycle is a measure of the exposure to the 
pollutant concentration being tested in the gas sample. 
Thus, the present invention may be used to test and 
measure even trace quantities of the test pollutants 
since the concentration thereof is integrated over the 
exposure time and the chemiluminescent light is re- 
leased in a very short period of time during the heating 
process. The limits on detection of trace amounts of the 
pollutants can therefore be increased by simply in- 
creasing the exposure time of the solid to the gas with 
no increase in the heating cycle being required for 
measuring the light output. 
In a similar operation of the present invention an 
unexposed sample 18 would be positioned within sam- 
ple holder 20 with covers 35 and 37 being removed and 
a test gaseous medium pumped through housing 12 via 
openings 34,36 to expose sample 18. After the desired 
time interval of exposure, the gas flow is stopped and 
heater element 21 actuated to heat the sample with the 
chemiluminescence of sample 18 being recorded, as 
before. 
Since the sample organic solid material is specific to 
the pollutant being tested, the presence of other gase- 
ous constituents do not interfere with the present in- 
vention. Thus, the presence of H2S, CO, NO, NO2, SO2 
and Nz do not interfere with the test of ozone when the 
sample organic solid is selected from rubrene, poly- 
(ethylene 2,6 naphthalene dicarboxylate) and 9,10 
diphenyl anthracene. Also, when the sample organic 
solid is selected from 3 3  diaminobenzoic acid and 
polyvinyl alcohol the test is specific for NO2 and vari- 
ous quantities of SO2, CO, NO, H2S, O2 and Nz in the 
gas will produce no light and will not degrade the sensi- 
tivity of the sample to NO2. The same specificity of 
polyvinyl pyrrolidone to CO prevents interference of 
this reaction with other constituents in a gaseous mix- 
ture. 
The system described is dry in the sense that no liquid 
solutions are required as in some known tests for these 
specific pollutants. The process as described herein- 
above is capable of detecting trace quantities of the 
pollutants using only thin layers of the sensitive organic 
solid material. For example, ozone in the 1-10 ppm 
range (in nitrogen) have been detected using only 
g of rubrene with a signal to noise ratio in excess of 
10: 1 after four minutes exposure to the ozone-nitrogen 
mixture. This sensitivity can be further increased using 
longer exposure times since the concentration mea- 
surement is integrated over the exposure time. 
As discussed hereinabove, it is not necessary to lo- 
cate the solid state sensitive material in the readout 
instrument. Samples could be placed at various loca- 
tions for monitoring average pollutant concentrations 
over a period of hours or days. These samples could be 
apart from the readout with a single instrument to elim- 
inate the expense of several electron packages. Also, 
the solid sensitive samples may be used for personal 
monitors to detect total exposure to the specific pollut- 
ants in much the same way that film badges are pres- 
ently used to monitor individual radiation exposure. 
This capability would be possible while still maintaining 
the sample protected from ambient light by enclosing 
the sample in a small container and utilizing a small 
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hand pump, or the like, to divert ambient air through 
the container to contact and expose the sample. Also, 
the solid organic samples described herein could be 
employed on thin film strips and adapted for controlled 
multiple exposure modes on a cassette-type pollution 
recording system. This latter packaging arrangement 
might prove particularly useful in aircraft, space flight 
and the like, where controlled time exposures to un- 
known gaseous environments could be tested and read 
out at postflight evaluation at a later date or by on- 
board readout equipment being signaled to rzmote 
stations, in a conventional manner. 
The materials for making the solid sensitive organic 
samples are inexpensive due to the small quantities 
needed, costing less than one cent per exposure, and 
capital equipment for accurate measurement of expo- 
sures can be centrally located and efficiently process 
hundreds of exposures per day. 
Rubrene samples suitable for use in the present pro- 
cess have been prepared by spraying a solution of 10% 
rubrene in benzene onto small flexible aluminum 
squares. The samples were allowed to dry and were 
maintained under a nitrogen atmosphere and heated 
until the inherent chemiluminescence was absent be- 
fore exposure to controlled concentration of ozone. 
Samples of rubrene have also been prepared by sublim- 
ing rubrene in vacua onto flexible aluminum strips. 
These samples were then exposed to known concentra- 
tions of ozone from 0.03 to 0.30 ppm over an exposure 
range of 0 to 60 minutes and measured by the appara- 
tus shown in FIG. 1 to confirm the operation of the 
present invention. 
Thin sheets of the other solid sample organic materi- 
als discussed hereinbefore are also readily available 
and can be conventionally adhered to flexible strips 
adaptable for use in the present process. Poly(ethy1ene 
2,6 naphthalene dicarboxylate), for example, is avail- 
able in film strips as thin as 0.254 mm. 
Since some of the solid organic sample materials will 
luminesce when exposed to light, all samples should be 
initially heated to the 100"-200"C. cycle and main- 
tained in darkness while cooled and during subsequent 
exposure and testing to eliminate false readings. 
Although the invention has been described relative to 
use of precise equipment and with specific illustrative 
examples, it is not so limited. There are obviously many 
modifications and variations of the present invention 
that will be readily apparent to those skilled in the art 
in the light of the above teachings. For example, one or 
all of the specific solid organic sample materials may be 
spaced along the same film strip so as to give exposure 
thereof simultantously or sequentially to the same test 
gas. Also, other materials than those specifically dis- 
closed may prove specific for one of the test pollutants 
discussed and other materials may subsequently be 
found specific for other pollutants not discussed herein. 
It is therefore to be understood that the invention may 
be practiced otherwise than as specifically described 
herein within the scope of the appended claims. 
What is claimed as new and desired to be secured by 
Letter Patent of the United States is: 
1. A method for detecting and measuring trace 
amounts of pollutants of the group consisting of ozone, 
nitrogen dioxide and carbon monoxide in a gaseous 
environment comprising: 
selecting a sample organic solid having the inherent 
property characteristics of chemically reacting 
3,977,83 1 
5 6 
with the gaseous pollutant being tested and thereaf- 
ter undergoing chemiluminesence when heated, 
exposing the selected sample organic solid material 
to an environment suspected of containing at least 
one of said pollutants, and reacting said solid mate- 5 solid is a thin vapor deposited rubrene layer, 
rial with said one of said pollutants, 
selected from the group consisting of rubrene, poly- 
(ethylene 2,6 naphthalene dicarboxylate), and 9,lO 
diphenyl anthracene. 
3. The method of claim 2 wherein the sample organic 
4. The method of claim 1 wherein the atmospheric 
pollutant tested is nitrogen dioxide and the sample 
3,5 diaminobenzoic acid and polyvinyl alcohol. 
5. The method of claim 1 wherein the atmospheric 
pollutant tested is carbon monoxide and the organic 
Solid is Polyvinyl pyrrolidone. 
heating the reacted sample organic solid material in 
the temperature range Of ooo-200"c~ for approxi- organic solid is selected from the group consisting of mately one minute, 
detecting and measuring the light output from the 
sample solid organic material during the heating 
cycle, 
recording the total integrated light intensity mea- 
sured during the heating cycle as a concentration 
of the specific pollutant being tested. 
2. The method of claim 1 wherein the atmospheric 
pollutant tested is ozone and the sample organic solid is 
6. The method of claim 1 wherein the atmospheric 
15 pollutant tested is ozone and the exposure to the solid 
organic solid is in the absence of light. 
* * * * *  
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Method for detecting pollutants

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