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Modification of a chemiluminescent ozone monitor for the measurement of gaseous unsaturated hydrocarbons
The Science of the Total Environment, 3 (1975) 323-328 © Elsevier Scientific Publishing Company, Amsterdam - Printed in Belgium
MODIFICATION OF A CHEMILUMINESCENT OZONE MONITOR FOR THE MEASUREMENT OF GASEOUS UNSATURATED HYDROCARBONS* N. Q U I C K E R T , W . J . F1NDLAY and J. L. M O N K M A N
Chemistry Division, Technology Development Branch, Air Pollution Control Directorate, Ottawa (Canada) (Received November 1st, 1974)
ABSTRACT
A chemiluminescent ozone monitor using the ozone-ethylene reaction has been adapted for measuring unsaturated hydrocarbons. The only change in the monitor was a replacement of the ethylene supply system with an electric discharge ozone source. Chemiluminescence was detected for all olefin-ozone reactions studied, including ethylene, substituted ethylenes (vinyl fluoride, chloride and cyanide), propylene, the butenes, 1,3-butadiene and several higher olefins. The intensity of chemiluminescence differed for the different olefins and appeared related to the ozoneolefin reaction rate. Saturated hydrocarbons and aromatics did not give a response. The minimum detectability for ethylene was 0.003 ppm and this value was somewhat lower for the higher olefins. Several important implications of the findings are discussed. These include the development of a more sensitive ozone monitor and the application of a total olefin monitor for the measurement of reactive hydrocarbons.
INTRODUCTION
The phenomenon of chemiluminescence has been successfully applied to the trace analysis of a number of air pollutants, notably nitrogen oxides 1 and ozone 2. For these compounds, commercial instrumentation is available for routine monitoring applications 3. Experiments have also been done to study the feasibility of chemiluminescence detection for such gases as carbon monoxide 1, sulfur dioxide 1 and total oxides of nitrogen (NO + N O 2 ) 1' 4. Chemiluminescence with certain hydrocarbons has been demonstrated by Krieger 5 using oxygen atoms as the reagent and Baity6 using active nitrogen. Both * Based on a presentation given at the 21st Canadian Spectroscopy Symposium, October 7-9, 1974, Ottawa, Canada.
323
of these studies required rather complicated instrumentation (high vacuum, microwave discharge, monochromator), which limits the application of these techniques for routine monitoring. The chemiluminescence of certain olefins with ozone has been reported 7'8 at pressures of 0.5 torr, although it is stated that no detectable chemiluminescence results at atmospheric pressure. This paper describes the application of a converted chemiluminescent ozone monitor to the measurement of unsaturated hydrocarbons. The initial phase of the work was to demonstrate that an ozone monitor, based on the ozone-ethylene reaction, could also be used for ethylene analysis. Subsequent experiments showed that the system also responded to a large number of other unsaturated hydrocarbons and could therefore play an important role in air pollution monitoring. EXPERIMENTAL Commercially available instrumentation was modified for the experiments. The analyzer used was an ozone monitor, model 612, manufactured by REM Incorporated*. The tubing which supplies ethylene to the reaction cell was disconnected and an ozone source was substituted. The ozone source with its power supply was obtained from a Leco Model CL-30 nitrogen oxide analyzer. The ozone source is typical of those used in commercially available oxides of nitrogen monitors and uses an electric discharge to produce ozone. A scrubber filled with charcoal was placed immediately after the reaction cell to destroy ozone which would otherwise damage the pump and flowmeter of the analyzer. All other features of the analyzer were used unchanged. It should be noted that any other ozone monitor (using chemiluminescence) could be similarly adapted. Oxygen was passed through the ozone source at 150 ml/min and the sampling flow-rate was 500 ml/min. The reaction cell of the analyzer was made of glass with a total volume of about 100 ml. The configuration of the entrance and exit ports was essentially the same as that described in the United States reference method for ozone 9. The output of the monitor was displayed on a strip chart recorder; the output range (for 03) was nominally 0-2 ppm. The ppm concentrations of gases for analysis were produced as follows. Mixtures of about 50 ppm (in N2) were prepared in metal cylinders using a recently published method lo. Concentrations in the low ppm range were obtained by diluting the cylinder mixture with a flow dilution system. The pure gases were C.P. grade and were used as received. RESULTS AND DISCUSSION Figure l shows the response of the converted ozone analyzer to ethylene and several other two- and three-carbon compounds. The response was linear with con-
* Address: 3107 Pico Boulevard, Santa Monica, Calif., U.S.A. 324
CO! ,,
C3H 6
/i// /
+¢
c,,,
+.c.,.cl
J
¢2H=F
2C~
C
=
2
l
~
3 4 ppm
5
6
Fig. 1. Chemiluminescent response as a function of concentration for acetylene, vinyl fluoride, vinyl chloride, ethylene and propylene.
trans 2 - G4He
iS 2 +C4HI
80-
t
t
/~114
~ 1°3-c4~6
7, / 6O
I / /
,i
/ P I~ 40
I /
I-C4Hs~
~ C , l l a
/
I
2
ppm
3
4
Fig. 2. Chemiluminescent response as a function of concentration for ethylene, l-butene, isobutene, cis-2-butene, trans-2-butene and !,3-butadiene. 325
centration except for propylene, which deviated from linearity above 1 ppm. Used as an ozone monitor, a response of 50 units corresponds to 1 ppm ozone. As an ethylene monitor, the response was about 40% of the ozone response, i.e., 20 units per ppm ethylene. The results confirm that the ozone--ethylene chemiluminescent reaction follows the simple relation 1 = k [ C 2 H , ] [03]
where 1 is the total light intensity, k is a constant and [C2H4] and [03] represent the concentrations of ethylene and ozone, respectively. When ozone is measured, [C2H4] is about 2% by volume. The ozone concentration used for ethylene measurement was not determined but was estimated to be about 1%. This would account for the lower response for ethylene measurement, assuming k a constant. The results indicate that a minimum detectability of 0.003 ppm ethylene is possible. This is about a factor of ten more sensitive than an analysis based on gas chromatography with flame ionization detection ~1. The minimum detection limits for the other compounds differ from ethylene as indicated by the slopes of the response curves shown in Fig. 1. In the present system some chemiluminescent response was noted with the analyzer sampling zero air. This background response had a magnitude of about 4 units and was therefore small with respect to the signals obtained during the measurements. It was possible to cancel out the background signal with the zero adjustment of the monitor. Such an effect has also been mentioned by Kummer et al. 7, who attributed the chemiluminescence to impurities adhering to the walls of the reaction cell. Figure 2 shows the responses obtained as a function of concentration for the five different four-carbon olefins. Ethylene is included for comparison. For the concentrations studied, trans-2-butene and 1,3-butadiene gave straight lines while cis-2-butene, 1-butene and isobutene gave curves. As in Fig. 1, there are considerable differences in the chemiluminescent responses for the different olefins. The response for trans-2-butene is about five times greater than the response for ethylene. This has important implications for chemiluminescent ozone monitors, since it implies that a more sensitive ozone monitor will result if the ozone-trans-2-butene reaction is employed. It is interesting to speculate why there are such large differences in sensitivity for similar compounds. The response of the instrument will depend on several factors, namely the reaction rate of ozone with the olefin, the nature of the chemiluminescent species formed and the spectral characteristics of the light-emitting species. The photomultiplier of the instrument sensed all radiation produced in the reaction cell since no optical filters were used. The maximum spectral response of the photomultiplier is limited, however, to the 400 nm region and decreases to about 50% at 500 nm. It has been shown that the ozone-ethylene chemiluminescence has its maximum intensity 7 at 430 nm while a higher olefin, trimethylethylene, had the maximum shifted to 520 nm (total pressure 0.5 torr). The lower overall response of the 1-butenes compared to ethylene may therefore be caused by the spectral response 326
characteristics of the photomultiplier. The reaction of ozone with 1-butene is 2.26 times faster than ozone with ethylene 12. For compounds where the light-emitting species is probably the same, the different responses can probably be traced to different reaction rates of the olefins with ozone. An example is the series ethylene, vinyl chloride and vinyl fluoride. In each case the chemiluminescent species is probably an excited formaldehyde 7'a. It is expected that the ozone reaction rate with the olefins decreases in the order ethylene, vinyl chloride and vinyl fluoride, since chlorine and fluorine are strongly electronegative and decrease the electron density of the double bond. In the same way, the electron donating properties of the methyl group in propylene lead to an increase in the ozone reaction rate 12. Cvetanovic12 has found that the reaction rate of ozone with propylene is 2.1 times faster than with ethylene, while the observed chemiluminescent response of propylene and ethylene differs by a similar amount, a factor of 1.8 (Fig. 1). The large difference in response between cis- and trans-butene-2 (Fig. 2) cannot be explained using only the difference in reaction rates. The trans isomer reacts 1.4 times faster than the cis isomer with ozone 12, while the chemiluminescent response ratio was found to be 2.4. Several different types of organic compounds were also sampled to determine whether any response would be obtained. It was found that gaseous mixtures of methane (10 ppm), propane (41 ppm) and carbon monoxide (22 ppm) gave no response. For compounds that were liquids, a sample of the vapour above the liquid was introduced into the monitor and the response noted. This procedure is a qualitative test and leads to rather large concentrations being sampled. No response was obtained for the paraffins pentane, cyclohexane and isooctane or the compounds methanol, acetone and formaldehyde. Aromatics such as benzene, ethylbenzene, dimethylnapthalene and xylene (ortho, meta and para) also gave no response. Compounds which did give a response were heptene, triisobutylene, nonene, 2,4-1utidine and vinyl cyanide. It appears, therefore, that the chemiluminescent response in this system is restricted to compounds containing olefinic bonds. The presence of atoms such as F, Cl and N does not prevent chemiluminescence from occurring, as long as the molecule contains a carbon-carbon double bond. From an analytical point of view, the converted ozone monitor represents a new and very sensitive detection system for the analysis of unsaturated hydrocarbons. There is no selectivity at this stage but a study of the spectral distribution of the chemiluminescence may allow some selectivity to be incorporated. In cases where only one olefin is present, the monitor may be used as described. It can also be used as a detection system after some pretreatment of the sample has occurred, e.g., the separation of components in a gas chromatographic column. The non-selectivity of the monitor is an advantage when considered from an air pollution point of view. It has been established that the most reactive hydrocarbons photochemicaily are olefins and substituted benzenes ~3"~4. Given the typical breakdown of hydrocarbons in air ~5 the measurement of total olefins is expected to represent the major fraction of the reactive hydrocarbon content. This has obvious advantages over the determination of non-methane hydrocarbons, a quantity which 327
also includes such non-reactive h y d r o c a r b o n s as ethane, p r o p a n e a n d i s o b u t a n e 15. A n i m p o r t a n t a d v a n t a g e o f the chemiluminescence d e t e c t i o n is t h a t the olefins are weighted a p p r o x i m a t e l y a c c o r d i n g to their p h o t o c h e m i c a l reactivity. It has been shown t h a t the o z o n e - o l e f i n reaction rate is the m a j o r factor which determines the reactivity o f the olefins in a s m o g system 13. A g o o d c o r r e l a t i o n has been o b t a i n e d by C v e t a n o v i c 12 when the o z o n e reaction rate was p l o t t e d a g a i n s t reactivity for a n u m b e r o f olefins. T h e o z o n e - o l e f i n reaction rate also plays a m a j o r role in d e t e r m i n i n g the chemiluminescent response a n d hence the m o n i t o r as described s h o u l d give a g o o d measure o f t o t a l reactive olefinic h y d r o c a r b o n s . Note added in p r o o f
F u r t h e r experiments were carried out to d e t e r m i n e whether increased sensitivities w o u l d result f r o m using olefins o t h e r t h a n ethylene for ozone m e a s u r e m e n t . S a m p l i n g 1 p p m o z o n e a n d using the same flow-rate o f the olefins ( 2 % by volume), the relative responses were: ethylene, 1; 1,3-butadiene, 1.4; trans-2-butene, 0.55; propylene, 0.61 a n d 1-butene, 0.33. This indicates t h a t the increase in response indir a t e d by Figs. 1 a n d 2 does n o t occur when the olefins are in g r e a t excess. 1,3-Butadiene does give a 4 0 % increase in sensitivity over ethylene. It is p r o b a b l e t h a t quenching is b e c o m i n g m o r e i m p o r t a n t u n d e r these c o n d i t i o n s a n d t h a t the higher olefins are m o r e effective at q u e n c h i n g the chemiluminescence. REFERENCES 1 2 3 4 5 6
A. Fontijn, A. J. Sabadell and R. J. Ronco, Anal. Chem., 42 (1970) 575. G. J. Warren and G. Babcock, Rev. Sci. lnstrum., 41 (1970) 280. R. K. Stevens and J. A. Hodgeson, AnaL Chem., 45 (1973) 443A. F. M. Black and J. E. Sigsby, Environ. Sci. Technol., 8 (1974) 149. B. Krieger, M. Malki and R. Kummler, Environ. Sci. TechnoL, 6 (1972) 742. F. M. Baity, W. A. McClenny and J. P. Bell, presented at 167th National ACS Meeting, Los Angeles, California, March 31-April 5, 1974.
7 W. A. Kummer, J. N. Pitts, Jr. and R. P. Steer, Environ. Sci. Technol., 5 (1971) 1045. 8 J. N. Pitts, Jr., W. A. Kummer, R. P. Steer and B. J. Finlayson, Advan. Chem. Set., 113 (1972) 246. 9 Reference Method for the Measurement of Photochemical Oxidants Corrected for Interferences Due to Nitrogen Oxides and Sulfur Dioxide, U.S. Federal Register, Vol. 36, No. 84, 1971,p. 8195. 10 J. C. Hilborn, W. J. Findlay and N. Quickert, Environ. Sci. TechnoL, to be published. 11 J. C. Hilborn and N. Quickert, Chem. Instrument., 6 (1975). 12 Y. K. Wei and R. J. Cvetanovic, Can. J. Chem., 41 (1963) 913. 13 N. Niki, E. E. Daby and B. Weinstock, Advan. Chem. Ser., 113 (1972) 16. 14 J. M. Heuss and W. A. Glasson, Environ. Sci. Technol., 2 (1968) 1109. 15 A. P. Altshuller, W. A. Lonneman, F. D. Sutterfield and S. L. Kopczynski, Environ. Sci. Technol.. 5 (1971) 1009.
328
MODIFICATION OF A CHEMILUMINESCENT OZONE MONITOR FOR THE MEASUREMENT OF GASEOUS UNSATURATED HYDROCARBONS* N. Q U I C K E R T , W . J . F1NDLAY and J. L. M O N K M A N
Chemistry Division, Technology Development Branch, Air Pollution Control Directorate, Ottawa (Canada) (Received November 1st, 1974)
ABSTRACT
A chemiluminescent ozone monitor using the ozone-ethylene reaction has been adapted for measuring unsaturated hydrocarbons. The only change in the monitor was a replacement of the ethylene supply system with an electric discharge ozone source. Chemiluminescence was detected for all olefin-ozone reactions studied, including ethylene, substituted ethylenes (vinyl fluoride, chloride and cyanide), propylene, the butenes, 1,3-butadiene and several higher olefins. The intensity of chemiluminescence differed for the different olefins and appeared related to the ozoneolefin reaction rate. Saturated hydrocarbons and aromatics did not give a response. The minimum detectability for ethylene was 0.003 ppm and this value was somewhat lower for the higher olefins. Several important implications of the findings are discussed. These include the development of a more sensitive ozone monitor and the application of a total olefin monitor for the measurement of reactive hydrocarbons.
INTRODUCTION
The phenomenon of chemiluminescence has been successfully applied to the trace analysis of a number of air pollutants, notably nitrogen oxides 1 and ozone 2. For these compounds, commercial instrumentation is available for routine monitoring applications 3. Experiments have also been done to study the feasibility of chemiluminescence detection for such gases as carbon monoxide 1, sulfur dioxide 1 and total oxides of nitrogen (NO + N O 2 ) 1' 4. Chemiluminescence with certain hydrocarbons has been demonstrated by Krieger 5 using oxygen atoms as the reagent and Baity6 using active nitrogen. Both * Based on a presentation given at the 21st Canadian Spectroscopy Symposium, October 7-9, 1974, Ottawa, Canada.
323
of these studies required rather complicated instrumentation (high vacuum, microwave discharge, monochromator), which limits the application of these techniques for routine monitoring. The chemiluminescence of certain olefins with ozone has been reported 7'8 at pressures of 0.5 torr, although it is stated that no detectable chemiluminescence results at atmospheric pressure. This paper describes the application of a converted chemiluminescent ozone monitor to the measurement of unsaturated hydrocarbons. The initial phase of the work was to demonstrate that an ozone monitor, based on the ozone-ethylene reaction, could also be used for ethylene analysis. Subsequent experiments showed that the system also responded to a large number of other unsaturated hydrocarbons and could therefore play an important role in air pollution monitoring. EXPERIMENTAL Commercially available instrumentation was modified for the experiments. The analyzer used was an ozone monitor, model 612, manufactured by REM Incorporated*. The tubing which supplies ethylene to the reaction cell was disconnected and an ozone source was substituted. The ozone source with its power supply was obtained from a Leco Model CL-30 nitrogen oxide analyzer. The ozone source is typical of those used in commercially available oxides of nitrogen monitors and uses an electric discharge to produce ozone. A scrubber filled with charcoal was placed immediately after the reaction cell to destroy ozone which would otherwise damage the pump and flowmeter of the analyzer. All other features of the analyzer were used unchanged. It should be noted that any other ozone monitor (using chemiluminescence) could be similarly adapted. Oxygen was passed through the ozone source at 150 ml/min and the sampling flow-rate was 500 ml/min. The reaction cell of the analyzer was made of glass with a total volume of about 100 ml. The configuration of the entrance and exit ports was essentially the same as that described in the United States reference method for ozone 9. The output of the monitor was displayed on a strip chart recorder; the output range (for 03) was nominally 0-2 ppm. The ppm concentrations of gases for analysis were produced as follows. Mixtures of about 50 ppm (in N2) were prepared in metal cylinders using a recently published method lo. Concentrations in the low ppm range were obtained by diluting the cylinder mixture with a flow dilution system. The pure gases were C.P. grade and were used as received. RESULTS AND DISCUSSION Figure l shows the response of the converted ozone analyzer to ethylene and several other two- and three-carbon compounds. The response was linear with con-
* Address: 3107 Pico Boulevard, Santa Monica, Calif., U.S.A. 324
CO! ,,
C3H 6
/i// /
+¢
c,,,
+.c.,.cl
J
¢2H=F
2C~
C
=
2
l
~
3 4 ppm
5
6
Fig. 1. Chemiluminescent response as a function of concentration for acetylene, vinyl fluoride, vinyl chloride, ethylene and propylene.
trans 2 - G4He
iS 2 +C4HI
80-
t
t
/~114
~ 1°3-c4~6
7, / 6O
I / /
,i
/ P I~ 40
I /
I-C4Hs~
~ C , l l a
/
I
2
ppm
3
4
Fig. 2. Chemiluminescent response as a function of concentration for ethylene, l-butene, isobutene, cis-2-butene, trans-2-butene and !,3-butadiene. 325
centration except for propylene, which deviated from linearity above 1 ppm. Used as an ozone monitor, a response of 50 units corresponds to 1 ppm ozone. As an ethylene monitor, the response was about 40% of the ozone response, i.e., 20 units per ppm ethylene. The results confirm that the ozone--ethylene chemiluminescent reaction follows the simple relation 1 = k [ C 2 H , ] [03]
where 1 is the total light intensity, k is a constant and [C2H4] and [03] represent the concentrations of ethylene and ozone, respectively. When ozone is measured, [C2H4] is about 2% by volume. The ozone concentration used for ethylene measurement was not determined but was estimated to be about 1%. This would account for the lower response for ethylene measurement, assuming k a constant. The results indicate that a minimum detectability of 0.003 ppm ethylene is possible. This is about a factor of ten more sensitive than an analysis based on gas chromatography with flame ionization detection ~1. The minimum detection limits for the other compounds differ from ethylene as indicated by the slopes of the response curves shown in Fig. 1. In the present system some chemiluminescent response was noted with the analyzer sampling zero air. This background response had a magnitude of about 4 units and was therefore small with respect to the signals obtained during the measurements. It was possible to cancel out the background signal with the zero adjustment of the monitor. Such an effect has also been mentioned by Kummer et al. 7, who attributed the chemiluminescence to impurities adhering to the walls of the reaction cell. Figure 2 shows the responses obtained as a function of concentration for the five different four-carbon olefins. Ethylene is included for comparison. For the concentrations studied, trans-2-butene and 1,3-butadiene gave straight lines while cis-2-butene, 1-butene and isobutene gave curves. As in Fig. 1, there are considerable differences in the chemiluminescent responses for the different olefins. The response for trans-2-butene is about five times greater than the response for ethylene. This has important implications for chemiluminescent ozone monitors, since it implies that a more sensitive ozone monitor will result if the ozone-trans-2-butene reaction is employed. It is interesting to speculate why there are such large differences in sensitivity for similar compounds. The response of the instrument will depend on several factors, namely the reaction rate of ozone with the olefin, the nature of the chemiluminescent species formed and the spectral characteristics of the light-emitting species. The photomultiplier of the instrument sensed all radiation produced in the reaction cell since no optical filters were used. The maximum spectral response of the photomultiplier is limited, however, to the 400 nm region and decreases to about 50% at 500 nm. It has been shown that the ozone-ethylene chemiluminescence has its maximum intensity 7 at 430 nm while a higher olefin, trimethylethylene, had the maximum shifted to 520 nm (total pressure 0.5 torr). The lower overall response of the 1-butenes compared to ethylene may therefore be caused by the spectral response 326
characteristics of the photomultiplier. The reaction of ozone with 1-butene is 2.26 times faster than ozone with ethylene 12. For compounds where the light-emitting species is probably the same, the different responses can probably be traced to different reaction rates of the olefins with ozone. An example is the series ethylene, vinyl chloride and vinyl fluoride. In each case the chemiluminescent species is probably an excited formaldehyde 7'a. It is expected that the ozone reaction rate with the olefins decreases in the order ethylene, vinyl chloride and vinyl fluoride, since chlorine and fluorine are strongly electronegative and decrease the electron density of the double bond. In the same way, the electron donating properties of the methyl group in propylene lead to an increase in the ozone reaction rate 12. Cvetanovic12 has found that the reaction rate of ozone with propylene is 2.1 times faster than with ethylene, while the observed chemiluminescent response of propylene and ethylene differs by a similar amount, a factor of 1.8 (Fig. 1). The large difference in response between cis- and trans-butene-2 (Fig. 2) cannot be explained using only the difference in reaction rates. The trans isomer reacts 1.4 times faster than the cis isomer with ozone 12, while the chemiluminescent response ratio was found to be 2.4. Several different types of organic compounds were also sampled to determine whether any response would be obtained. It was found that gaseous mixtures of methane (10 ppm), propane (41 ppm) and carbon monoxide (22 ppm) gave no response. For compounds that were liquids, a sample of the vapour above the liquid was introduced into the monitor and the response noted. This procedure is a qualitative test and leads to rather large concentrations being sampled. No response was obtained for the paraffins pentane, cyclohexane and isooctane or the compounds methanol, acetone and formaldehyde. Aromatics such as benzene, ethylbenzene, dimethylnapthalene and xylene (ortho, meta and para) also gave no response. Compounds which did give a response were heptene, triisobutylene, nonene, 2,4-1utidine and vinyl cyanide. It appears, therefore, that the chemiluminescent response in this system is restricted to compounds containing olefinic bonds. The presence of atoms such as F, Cl and N does not prevent chemiluminescence from occurring, as long as the molecule contains a carbon-carbon double bond. From an analytical point of view, the converted ozone monitor represents a new and very sensitive detection system for the analysis of unsaturated hydrocarbons. There is no selectivity at this stage but a study of the spectral distribution of the chemiluminescence may allow some selectivity to be incorporated. In cases where only one olefin is present, the monitor may be used as described. It can also be used as a detection system after some pretreatment of the sample has occurred, e.g., the separation of components in a gas chromatographic column. The non-selectivity of the monitor is an advantage when considered from an air pollution point of view. It has been established that the most reactive hydrocarbons photochemicaily are olefins and substituted benzenes ~3"~4. Given the typical breakdown of hydrocarbons in air ~5 the measurement of total olefins is expected to represent the major fraction of the reactive hydrocarbon content. This has obvious advantages over the determination of non-methane hydrocarbons, a quantity which 327
also includes such non-reactive h y d r o c a r b o n s as ethane, p r o p a n e a n d i s o b u t a n e 15. A n i m p o r t a n t a d v a n t a g e o f the chemiluminescence d e t e c t i o n is t h a t the olefins are weighted a p p r o x i m a t e l y a c c o r d i n g to their p h o t o c h e m i c a l reactivity. It has been shown t h a t the o z o n e - o l e f i n reaction rate is the m a j o r factor which determines the reactivity o f the olefins in a s m o g system 13. A g o o d c o r r e l a t i o n has been o b t a i n e d by C v e t a n o v i c 12 when the o z o n e reaction rate was p l o t t e d a g a i n s t reactivity for a n u m b e r o f olefins. T h e o z o n e - o l e f i n reaction rate also plays a m a j o r role in d e t e r m i n i n g the chemiluminescent response a n d hence the m o n i t o r as described s h o u l d give a g o o d measure o f t o t a l reactive olefinic h y d r o c a r b o n s . Note added in p r o o f
F u r t h e r experiments were carried out to d e t e r m i n e whether increased sensitivities w o u l d result f r o m using olefins o t h e r t h a n ethylene for ozone m e a s u r e m e n t . S a m p l i n g 1 p p m o z o n e a n d using the same flow-rate o f the olefins ( 2 % by volume), the relative responses were: ethylene, 1; 1,3-butadiene, 1.4; trans-2-butene, 0.55; propylene, 0.61 a n d 1-butene, 0.33. This indicates t h a t the increase in response indir a t e d by Figs. 1 a n d 2 does n o t occur when the olefins are in g r e a t excess. 1,3-Butadiene does give a 4 0 % increase in sensitivity over ethylene. It is p r o b a b l e t h a t quenching is b e c o m i n g m o r e i m p o r t a n t u n d e r these c o n d i t i o n s a n d t h a t the higher olefins are m o r e effective at q u e n c h i n g the chemiluminescence. REFERENCES 1 2 3 4 5 6
A. Fontijn, A. J. Sabadell and R. J. Ronco, Anal. Chem., 42 (1970) 575. G. J. Warren and G. Babcock, Rev. Sci. lnstrum., 41 (1970) 280. R. K. Stevens and J. A. Hodgeson, AnaL Chem., 45 (1973) 443A. F. M. Black and J. E. Sigsby, Environ. Sci. Technol., 8 (1974) 149. B. Krieger, M. Malki and R. Kummler, Environ. Sci. TechnoL, 6 (1972) 742. F. M. Baity, W. A. McClenny and J. P. Bell, presented at 167th National ACS Meeting, Los Angeles, California, March 31-April 5, 1974.
7 W. A. Kummer, J. N. Pitts, Jr. and R. P. Steer, Environ. Sci. Technol., 5 (1971) 1045. 8 J. N. Pitts, Jr., W. A. Kummer, R. P. Steer and B. J. Finlayson, Advan. Chem. Set., 113 (1972) 246. 9 Reference Method for the Measurement of Photochemical Oxidants Corrected for Interferences Due to Nitrogen Oxides and Sulfur Dioxide, U.S. Federal Register, Vol. 36, No. 84, 1971,p. 8195. 10 J. C. Hilborn, W. J. Findlay and N. Quickert, Environ. Sci. TechnoL, to be published. 11 J. C. Hilborn and N. Quickert, Chem. Instrument., 6 (1975). 12 Y. K. Wei and R. J. Cvetanovic, Can. J. Chem., 41 (1963) 913. 13 N. Niki, E. E. Daby and B. Weinstock, Advan. Chem. Ser., 113 (1972) 16. 14 J. M. Heuss and W. A. Glasson, Environ. Sci. Technol., 2 (1968) 1109. 15 A. P. Altshuller, W. A. Lonneman, F. D. Sutterfield and S. L. Kopczynski, Environ. Sci. Technol.. 5 (1971) 1009.
328