Certain Regularities in the Composition of Volatile Organic Pollutants in the Urban Atmosphere B. V. loffe", V. A. Isidorov, and 1. G. Zenkevich Chemistry Department, Leningrad State University, 199164 Leningrad, USSR
w Data are reported for a detailed comparative analysis of organic compounds in the atmosphere of six large cities in the USSR, in different geographic and climatic zones using a uniform methodology to eliminate methodological differences between the sampling sites. Organics were concentrated on hydrophobic carbonaceous sorbents and subsequently analyzed by GC and GC/MS. The qualitative composition of the hydrocarbons collected was relatively constant. Atmospheric C4-C13 hydrocarbons were comprised of paraffins (-50%), aromatic compounds (-3o%), and alkenes (--10-20%), regardless of geographic location. Divergencies in the quantitative group composition are found in cities with specific additional sources of pollution (e.g., increased levels of naphthenes and olefins were observed near deposits of naphthenic oil and large petrochemical plants, respectively). It is suggested that the toluene/benzene ratio in air cannot serve as a reliable criterion for the significance of exhaust gases as a source of atmospheric hydrocarbon pollutants; instead of this, the ratio of the sum of aromatic hydrocarbons to the sum of paraffins is suggested as a more reliable value. It is also shown that the direct evaporation of automobile fuel can represent a n important source of hydrocarbon pollutants in air. Detailed information on the composition of organic micropollutants in the urban atmosphere is of great interest for establishing certain regularities and peculiarities due to geographical, climatic, and other factors. T o obtain strictly comparable data, detailed information on the composition of organic pollutants should be obtained under identical conditions. Unfortunately, only a limited number of papers have reported on the detailed analysis of volatile organic pollutants present in the atmosphere. In these, analyses were carried out using different methods, and different sorbents were used for the preconcentration of the trace components. This is regrettable because recent comparative tests of the sorbents used have shown great differences in their sorbing capacities ( I , 2). At present, not a single existing sorbent can meet all the requirements. An ideal sorbent should exhibit high thermal stability and no catalytic activity a t desorption temperatures, have high capacity for a wide range of organic compounds of various classes, and exhibit little affinity for water. Unfortunately, the range of sorbents satisfying even two of these three requirements is fairly limited. Such thermally stable and hydrophobic materials as Tenax GC and thermally graphitized carbon blacks sorb only very slightly the compounds with low molecular weight and polar compounds; on the other hand, hydrophobic polymers of the Porapak Q type have high sorption capacity for organic compounds but are not thermally stable. Activated charcoal has a high affinity for organic compounds, but thermal desorption from its surface is difficult and is often accompanied by chemical modification of the substances. This may be avoided by recovering the pollutants by extraction or elution with a solvent; however, this procedure is more complex and involves a loss in sensitivity as a result of dilution. This problem can be solved by using complex sorbents consisting of several substances with complementary properties. However, for the selection of a satisfactory system, first a detailed study of the principles of a combination of different sorbents is necessary. This was the aim of our investiga864
Environmental Science & Technology
tions. In the present work, layers of carbonaceous sorbents differing in their sorption properties, placed consecutively in a concentrator tube, were used for the condensation of atmospheric trace pollutants. We have used two sorbents: Carbochrome K-5 ( 3 ) and PSKT, a new 'material developed by Professor A. V, Kiselev (State University, Moscow) by depositing pyrocarbon on S K T , a commercial activated charcoal. Another important problem in the investigation of the nature and sources of atmospheric pollutants is the establishment of convenient and reliable criteria for the comparative characterization of the composition of volatile organic pollutants. In this work the group composition of the hydrocarbons is used as such a criterion. This method has been used for a long time in the petroleum industry and permits a direct comparison with the composition of oil products. Experimental
Sorbents Used and Their Characteristics. Specific retention volumes (V,) of representative compounds were determined with a Model Tsvet 6 gas chromatograph by using a stainless steel column (500 cm x 2 mm i.d.1, FID, and nitrogen as the carrier gas (30 mL/min), at 4-6 different temperatures ranging from 140 to 220 "C for Carbochrome K-5 and Carbopack B and from 160 to 380 "C for PSKT. Retention times a t each temperature were measured at least three times, and the calculated values of the specific retention volumes were extrapolated to 20 "C by the least-squares method, assuming the well-known linear relationship between log V , and 1/T (where T is the column temperature, in K). Table I lists the comparative data for Carbochrome K-5, Carbopack B, and P S K T obtained from Professor Kiselev. In its sorption properties, P S K T occupies an intermediate position between the activated charcoals and thermally graphitized carbon blacks. As a result of the modification of activated charcoal with pyrocarbon, the surface of P S K T becomes hydrophobic. T h e adsorption of water vapor by the initial S K T charcoal is 45 mg/g, while for P S K T this value is 3.5 mg/g and is close to the value for Tenax GC (1-6 mg/g). The values of V , show that P S K T adsorbs organic substances of various classes much better than the graphitized carbon blacks. This makes it possible to use such modified carbonaceous sorbents for trapping even the most volatile compounds. However, this sorbent retains too much of the relatively high boiling compounds. Hence, in this work a complex adsorbent was used consisting of consecutive layers of Carbochrome and PSKT. The weight ratios of the sorbents were selected in such a way that when 10 L of gas was passed through them, C; and higher hydrocarbons were completely retained by the Carbochrome layer. T h e minimum amount of the sorbent ensuring complete trapping of the analyzed substances was calculated by the method described by Cropper and Kaminsky ( 4 ) . T h e results of the calculation showed that when the air volume is 10 L and the temperature is 20 "C, toluene and acetone should be virtually completely retained by 0.8 g of Carbochrome and 0.5 g of PSKT. Sampling and Analysis. Air sampling was performed in six large cities of the USSR, Baku, Kemerovo, Leningrad, Murmansk, Tashkent, and Tbilisi. These cities are located in zones with widely differing geo-
0013-936X/79/0913-0864$01 .OO/O @ 1979 American Chemical Society
Table 1. Comparative Characteristics of Carbon-Based Sorbents SP surface sorbent
Carbopack B Carbochrome K-5
PSKT a
adsorptlon of H20
area, m2/g
vapor, mg/g
100 1 10 740
sp retention vol, Ve, L/g, 20 OC
* ethanol
acetone
0.1
0.08
0.1
0.1 3.5
0.04 9.9
0.08 35
chloroform
hexane
benzene
toluene
6.6
1.o
6.2
2.5
35
6.6 1 x 106
1.6 9 x 104
4.8
4.2 4 x 105
24
0.3 0.6, 380
Weight increase after passing 10 L of air with an absolute humidity of 11 mg/L at 18 ' C .
graphical and cliinatic conditions, including the Arctic region (Murmansk), the dry subtropics of the Transcaucasus (Tbilisi), the sea climate of the Baltic sea shore (Leningrad),and the continental climate of Siberia and central Asia (Tashkent and Kemerovo). Altitudes in these cities range from sea level to a height of 400 m. These are the first detailed analyses to be carried out on the Asiatic continent (Tashkent and Kemerovo), to the north of the Polar Circle (Murmansk), and in the immediate vicinity of oil fields (Baku). Stainless steel sampling tubes (210 mm X 6.5 mm i.d.) were filled with layers of 0.8 g of Carbochrome K-5 (with a particle size of 0.215-0.315 mm) and 0.5 g of PSKT (with a particle size of 0.25-0.50 mm) separated by glass wool. Prior to application, these tubes were heated for 20 min a t 500 "C in a helium flow (30 mL/min). Sampling was performed simultaneously in three tubes in such a manner that the air first passed through the Carbochrome layer. As a rule, sampling was made a t noon in dry sunny weather by passing 10 L of air a t a rate of 0.2 L/min. Thermal desorption was carried out for 20 min at 400 "C into a 50 m X 0.36 mm i.d. copper capillary column coated with dinonyl phthalate, the first section of which was cooled with liquid nitrogen. (This desorption temperature of 400 "C is possible for carbonaceous sorbents of this type ( 5 ) .Our specific experiments have confirmed this.) In the course of desorption helium passed in the direction opposite to that of the air flow during sampling. After desorption, the mixture was chromatographed by programming the temperature of the column (after the temperature of the first section was also raised to 30 "C) from 30 to 125 "C a t a rate of 3 "C/min, with a subsequent isothermal period a t 125 "C. From one of the simultaneously obtained samples identification was carried out by GC/MS (with an LKB Model 2091 mass spectrometer), while in another sample the pollutants were analyzed quantitatively by gas chromatography with a flame ionization detector on which the relative response factors of hydrocarbons of various classes are close to unity. T h e conditions of recording of the mass spectra have been described previously (3);the ionization voltage when recording the chromatograms was 20 eV. Use of Linear Retention Indices in the Identification of Atmospheric Pollutants. Linear retention indices (6) were calculated from the retention times recorded with an electronic integrator
z = 100[2 + ( t - t,)/(t,+1 - t , ) ]
(1)
where t , t,, and t z + l are the retention times for a given component and the n-alkanes emerging just before and after this component, having the number of carbon atoms of 2 and ( z + l ) ,respectikely. The linear retention index system can be used both when the temperature rise is linear and when an isothermal period exists and is very convenient for the identification of atmospheric pollutanis, since most of its reference peaks (n-alkanes) are already among the permanent constituents of the modern urban atrnosphere and, thus, are always present in the
CyClOhexane
hexene-2
* Supelco Inc., Bellefonte, Pa
chromatogram. Moreover, for the calculation of the linear retention indices one does not have to determine the gas holdup time, in contrast to the widely used Kovats retention index system. This is very important because, due to the way of sample collection and transfer into the column, it is difficult to establish the "start point" and the true gas holdup time. When mass spectrometric d s t a are supplemented with retention indices, an unequivoczl identification of the peaks in the chromatograms is possible n those cases where the signals of the main ions alone in the riass spectra are not sufficient to identify isomers (aromatic h jdrocarbons, some naphthenes and olefins; see Table 11). 7 he combination of the mass spectrometric and chromatog .aphic information permitted us to increase the ratio of completely identified constituents to about 60%. Under the conditions used, the mean error in determining the linear retention indices was &1 index unit. The ranges of indices of organic pollutants found in the atmosphere overlap only in a few cases. Consequently, in duplicate experiments it is not necessary to record the mass spectra, and the identification of the constituents can be made from the retention indices alone. The list of linear retention indices developed for atmospheric pollutants can be entered in the memory of a small computer. Thus, the treatment of a chromatogram containing about 100 peaks, including converting the integrator readings and printing out the list of the identified constituents, takes only about 20 min. Results and Discussion Sampling of atmospheric air was carried out in central residential districts of these cities about noon, usually in dry sunny weather with the exception of two cases: in Murmansk and Kemerovo sampling was carried out in cloudy weather (in Murmansk during a slight snowfall). The total number of organic pollutants detected in the air samples of these six cities was 146, 135 of them being hydrocarbons listed in Table 11. They include all 10 normal Cd-CI3 paraffins and 32 branched paraffins, 52 hydrocarbons with the composition of C,H2,, 36 aromatic Cc-Cl2 hydrocarbons, and five terpenes. About half of these hydrocarbons (66) were found in the air of all six cities, and they constitute 75-95% of the total amount of the Cd-C13 organic pollutants in the urban atmosphere. Concentrations of the detected compounds ranged from 0.001 to 0.7 mg/m3. Most of the permanent constituents are petroleum hydrocarbons. Almost all other pollutants in Table I1 were also identified several times, and 90% of them were found in a t least three cities. If we bear in mind that most of these constituents have also been found in the air of Zurich, Switzerland (121, Houston, Tex. (121, and Paris, France ( 5 ) ,it can be concluded that the qualitative composition of volatile pollutants in the atmosphere of large modern cities is very similar and permanent. In contrast to the data of other authors (5,11,12),a characteristic feature of the data reported here and in our previous paper ( 3 ) is the presence of a large number of unsaturated Volume 13, Number 7, July 1979
865
Table II. C4-C13 Hydrocarbons, Detected in the Air of Six Industrial Cities of the USSR serial no.
1 2 3 4
5 6 7 8 9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
866
hydrocarbon a
linear retention index
ldent method
n-butane trans-butene-2 cis-butene-2 2-methylbutane n-pentane n-pentene 2,2-dimethylbutane 2,3-dimethylbutane
400 419 430 464
115
500-
I
514 526 536
1115
C5H8 2-methylpentane 3-methylpentane n-hexane n-hexene
536 559 577 600 604 61 1 619 628 639 650 657 665 669 683 690 694 700 704 714 720 724 730 739
IV I I I Ill IV
+ cyclopentane
Cd12 2,4-dimethylpentane methylcyclopentane C7H14 3,3-dimethylpentane Pmethylhexane cyclohexane 3-methylhexane trans-I ,3-dimethylcyclopentane
cis-1.3-dimethylcyclopentane trans-l,2-dimethylcyclopentane n-heptane n-heptene C7H14
cis-l,2-dimethylcyclopentane benzene methylcyclohexane 1-trans-2-cis-4-trlmethylcyclopentane l-trans-2-cis-3-trimethylcyclopentane 2-methylheptane 4-methylheptane 3-methylheptane C8H16
CeH16 C8H16
trans- 1,4-dimethylcyclohexane n-octane n-octene trans- 1,2-dimethylcyclohexane dimethylcyclohexane isononane isononane toluene C8H16 (naphthene) efhylcyclohexane tfimethylcyclohexane CSH18 2-methyloctane 3-methyloctane trimethylcyclohexane C9H18 C9H18 C9H18 C9H 18 GHie C9Hie C9H18
Environmental Science & Technology
serial no.
115
61
114 GC (I4 GC
62 63 64
ii6c llSC
I I
IV I I I I llgd
llgd 118d
I 111 IV l18d I I
65 66 67 68 69 70 71 72
hydrocarbon a
n-nonane n-nonene methylethylcyclohexane methylethylcyclohexane isodecane isodecane methy lethy lcyclohexane ethylbenzene isodecane isodecane
73 74
ClOHI6 (terpene) p-xylene m-xylene a-pinene
75 76 77 78 79 80 81 82
C1oHzo CioHzo isodecane 2-methylnonane isodecane 3-methylnonane camphene 0-xylene
83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
CioHzo cumene styrene n-decane n-decene C10H20 isoundecane n-propylbenzene
Id
101
I Ill Id 111 111 Ill I 111 I
102 103 104
CioHzo m-ethyltoluene p-ethyltoluene A3-carene (?) butylcyclohexane mesitilene o-ethyltoluene isoundecane isoundecane limonene N -methylstyrene 1,2,44rlmethylbenzene m-cymene p-cymene
105 106 107 108 109
CiiHzz n-undecane n-undecene o-cymene methylstyrene
isododecane 1,2,3-trimethylbenzene mpropyltoluene n-butylbenzene p-propyltoluene 1,3-dimethyl-5-ethylbenzene indan
IV IV
110 111 112 113 114 115 116 117 118 119 120
IV
121
IV
122
Id
746
ll8d
757 761 767 772
I I I IV
778 784 794 800 805 812 816 822 828 834 840 845 849 852 859 867 870 874 880 884 888 890 892 895
IV IV
111
IV I I 111 IV IV IV
C i iHzz indene dimethylethyl benzene dimethylethylbenzene CllH24 n-dodecane
linear retention index
ident method
9000 905 908 911 915
I 111 Ill Ill 111 Ill 111 I 111 111 111 le
918 923 928 933 936 938 942 945 951 952 955 958 962 965 969 972 973 98 1 986 994 1000 1005 1009 1012 1018 1022 1031 1033 1039 1047 1053 1056 1062 1069 1073 1074 1078 1084 1093 1097 1100 1106 1106 1110 1111 1113 1128 1127 1122 1131 1136 1158
1195 1200
le
I IV IV 111
I 111 I I le
IV l13e 115
I 111 IV 111 l13e IV 115 e
l15e I I13d 115 e
l15e Ill 111 I 115
l15e l13e )I3e IV I Ill Ilge 111 111 l15e
)I4e 1158
114 e lIqe 115
IV 113
Ill Ill IV I
Table II. Continued serial no.
123 124 125 126 127 128
hydrocarbon a
n-dodemcene 1,2,4,5- andlor 1,2,3,5tetramethyl benzene n-amylhenzene
llnear retention Index
linear retention index
ident method
aerlai no.
Ill
129 130 131 132
n-tridecene dimethylindan (?)
133 134 135
n-hexylbenzene diphenyl naphthalene
1214
)I3
1222
113
methylindan methylindan
Ill 111
1,2,3,44etramethylbenzene
113
e
hydrocarbon a
ident method
Ill I 111 111
isotridecane
n-tridecane
1300
113 114 114
Compounds detected in ail six cities are italicized. I, individual identificationfrom complete mass spectra by comparison with data in the Atlas (7) or with spectra of known reference samples. 11, individual identification by the strongest peak indicated by subscript, using the Eighth Peak Index ( 8 ) .Ill, classification with a group of isomers with known structural fragments. IV, determination of the molecular formula by the mass numbers of the molecular ions and strong fragmentations. When literature data 'were used, the reference number is indicated: ref 6 ref 9: e refi 10. a
Table 111. Group Composition of C4-CI2 Hydrocarbons Determined Individually in City Air, in a Commercial Gasoline, and in Exhaust Gasa ( % ) hydrocarbons Cnkntz
City, daleb
-,
Murmansk 3/17/77' Leningrad 5 / 4 / 7 7 Leningrad 6/23/77 Leningrad 7/4/77 Kemerovo 7/14/77' Tashkent 7/19/77 Tashkent7/20/77 Tbilisi 5/24/77 Baku 5 / 1 9 / 7 7 Baku5/20/77 Baku5/20/77 gasoline exhaust gas
aromatlc hydrocarbons
sum of permanent compds
r (see Eq 2 )
97 94 95
23 21 23
33 38 31 34 20 34 26 34 28 35 26
75 94 89 92 86 94 83
0.6 0.9 0.6 0.6 0.4 0.7 0.6 0.7 0.8 1.1 0.6
7 1
33 63
89 90
0.6 2.6
C n Hzn
temp, OC (RH, %)
sum total
n-alkanes
sum total
naphthenes
-3.8 (89) 12.3 (31) 11.9 (42) 17.6 (78) 24.0 (77) 34.6 (16) 33.0 (18) 25.4 (35) 25.2 (14) 24.0 (23) 25.0 (23)
56 41 54 56 46 46 46 48 35 32 41
25 24 26 24 22 23 22 22 16 16 17
11 21 15 10 34 20 28 18 37 33 33
8 10 7 7 8 12 11 11
59 24
25 11
8 13
97
a Using the same gasoline as analyzed for this table. Month/day/year. Samples were collected by passing 0.5 L of exhaust gas through tubes containing the sorbent, located at a distance of 0.5 m from the exhaust pipes of a Volga automobile. Further analysis was carried out similarly to the analysis of atmospheric air.
C 4 H ~ - C 9 H 1hydrocarbons. ~ This discrepancy is mainly due to the difference in the conditions of sampling: in our experiments the volumes of air for sampling were much smaller and as a rule did not exceed the value of V , for olefins on carbonaceous sorbents. Apart from hydrocarbons, the air of the cities investigated contains acetone, diethyl ether, dioxane, a C ~ H 1 4 0compound, and a series of halogen derivatives: n-propyl chloride, isopropyl chloride, n-butyl chloride, n-propyl bromide, trichloroethylene, tetrachloroethylene, and chlorobenzene. Depending upon weather conditions, the distances from pollution sources, and the time and place of sampling, the concentrations of organic pollutants in the atmosphere can vary 10- to 20-fold. Knowledge of the absolute concentrations is necessary for the hygienic characterization of the air, but data concerning the relative content of constituents are no less important. It has been suggested that the measurement of the concentration rat io of toluene to benzene should serve as an index for revealing the sources of atmospheric hydrocarbon pollutants (13). [n automobile exhaust gases the toluene/ benzene ratio varied from 1.0 to 2.8, the average being 1.8. In the cities of North America (Los Angeles, Calif., and Toronto, Ontario, Canada) it was much higher (2.4-2.5) (13),while in Zurich, Switzerland, it was much lower (0.7) (11).It has been attempted to interpret the great variations in this value as a result of differences in the climatic conditions, the gasoline
composition, and the sources of pollution. In particular, it has been suggested t h a t one reason for relatively high toluene concentrations is the added source from evaporation of solvents and gasoline (13). In our opinion, the toluenehenzene ratio is not very suitable for investigating the sources of atmospheric pollution. The range of this ratio is too wide both in crude oil and in motor fuel. Our experimental data for 15 samples of straight-run gasolines a t nine factories showed t h a t the toluene/benzene ratio varies over a range from 1.6 to 19.7, having an average value of 4.6. Reforming gasolines obtained from this raw material are characterized by the variation of this ratio from 3.6 to 20.9 (the average value being 7.1), whereas a direct comparison of the data obtained for a gasoline sample and for the exhaust gases of a Volga car using this fuel shows that after the combustion process the toluene/benzene ratio changed only from 3.7 to 1.2, Le., by much less than the possible differences in various fuel samples. Moreover, both benzene and toluene are produced in large scale a t factories which, in themselves, are sources of pollutants having no relationship to motor transport. To reveal the sources of complex mixtures of volatile hydrocarbons in the atmosphere, hydrocarbon group composition values are more suitable than those of any individual compound. These have been used for a long time in the petroleum chemistry and permit a direct comparison of the Volume 13, Number 7, July 1979
867
composition of atmospheric constituents, oils, and oil products. Table 111shows the calculated values of the group composition of C*-C12 hydrocarbons in urban air and also in a commercial gasoline used most widely in the USSR. These data show that paraffins make up the main fraction (about half) of atmospheric Cd-Cl2 hydrocarbons. They are followed by aromatic hydrocarbons (about one-third) and finally by hydrocarbons of the C,H2, series (10-20%). Considerable variations in the group composition of atmospheric hydrocarbons observed in some cases are probably caused by local factors rather than by geographical or climatic conditions. Thus, the presence of a large number of naphthene hydrocarbons in the air of Baku is due to the specific composition of local oils. Considerable local differences in the group composition are accompanied by a noticeable decrease in the fraction of permanent constituents found in all cities. Moreover, nonpermanent constituents in Kemerovo and in one location in Tashkent proved to be olefins (20 and 7% of the total amount of hydrocarbons, respectively). Doubtless, apart from industrial exhaust gases, the exhaust gases of automobiles are also sources of olefins. In their toxicity olefinic hydrocarbons are 100-fold more dangerous than paraffins and approach the aromatic hydrocarbons. The presence of considerable amounts of unsaturated hydrocarbons in the urban atmosphere makes it necessary to develop simple and reliable methods for the routine control of their content. It is of great interest to establish the part played by exhaust gases in the formation of the composition of hydrocarbon constituents in the atmosphere. On the whole, the group composition of hydrocarbons in the atmosphere greatly differs from that of exhaust gases and approaches that of automobile fuel. The most convenient parameter for such comparisons is the ratio ( r ) of the sum of aromatic hydrocarbons to the sum of paraffins:
This parameter is relatively constant in the samples of reforming gasoline (0.73 & 0.15) and straight-run gasolines used as raw material for their production (0.18 & 0.03). The exhaust gases of automobile engines are characterized by a much higher value of r , since paraffinic hydrocarbons are burned more completely in the engine. The values of r found by us in the urban atmosphere vary in the range from 0.4 to 1.1,having an average value of 0.7 that virtually coincides with the data for the most common gasoline and is severalfold lower than
868
Environmental Science & Technology
the value for the exhaust gas. This interesting fact suggests that the evaporation of automobile fuel is a very important source of hydrocarbon emission into the urban atmosphere. Data reported by Leonard et al. (14) provide an idea as to the possible scope of this source of pollutants: in such a large city as Los Angeles, in 1965, the total loss of gasoline due only to evaporation was 350 tons per day. Hence, the control of atmospheric pollution by automobile transport should not be restricted to decreasing the content of toxic components in exhaust gases: it is equally important to prevent fuel evaporation during its storage and handling.
Acknowledgments The authors are greatly indebted to Professor A. V. Kiselev and Dr. N. V. Kovaleva (State University of Moscow, USSR) for providing a sample of the new PSKT sorbent, and wish to express their gratitude to Dr. L. S. Ettre (Perkin-Elmer Corporation, Norwalk, Conn.) for his help in the preparation of the manuscript and for editing the English text. Literature Cited (1) A. A. Isidorov, I. G. Zenkevich, and B. V. Ioffe, Dokl. A k a d . Nauh
S S S R , 235,618 (1977). ( 2 ) P. Ciccioli, G. Bertoni, E. Brancaleoni. R. Fratarcangeli, and F. Brunei-, J . Chromatogr., 126,757 (1976). (3) B. V. Ioffe, V. A. Isidorov, and I. G. Zenkevich, J . Chromatogr., 142,787 (1977). (4) P. R. Cropper and S. Kaminsky, A n d . Chem., 35,735 (1963). (5) A. Raymond and G. Guiochon, Enuiron. Sci. Technol., 8 , 143 (1974). (6) M. S. Vigdergauz and A. A. Martynov, Chromatographia, 4,463 (1971). (7) E. Stenhagen, S. Abrahamsson, and F. W. McLafferty, Eds., “Atlas of Mass Spectral Data”, Vol. 1, Interscience, New York, 1969. (8) “Eighth Peak Index of Mass Spectra”, Mass Spectrometry Data Centre, Aldermaston, 1970. 19) N. I. Vvkhrestvuk. V. P. Levenets, A. P. Lizomb. A. S.Zhurba, E. K. Bryanskaya, Yu. A. Slupitskii, and E. P.-Sobol’, Zh. A n d . C h i m . , 26,2007 (1971). 110) H. Mivake. M. Mittoka. and T. Matsumoto. Bull. C h e m . SOC. Jpn., 38,“1062 (1965). i l l ) K. Grob and G. Grob, J . Chromatogr., 62,1(1971). (12) W. Bertsch, 8. C. Chang, and A. Z k k i s , J . Chromatogr. Sci., 12,175 (1974). (13) S. Pilar and W. F. Graydon, Enuiron. Sci. Technol., 7, 628 (1973). (14) M. J. Leonard, E. I. Fisher, M. F. Brunelle, and J. E. Dickinson, J Air Pollut. Control Assoc., 26,359 (1976). Received for reuieu November 8, 1978. Accepted April 9, 1979.
