erate the olefin. The interference of benzene in the analytical method for the determination of olefin? in concentrated sulfuric acid has been determined b y generating benzene and 1-hexene in two parallel diffusion cells, The sensitivity of a gas chromatographic detector to benzene a as measured b y using a diffusion cell to prepare a benzene in helium gas mixture. The response of a mass spectrometer to several hydrocarbons in the 10- to 100p.p.m. range was ascertained b y passing the hydrocarbon in air or nitrogen gas stream past the capillary inlet system of the mass spectrometer. Diffusion cells have also been used in a preliminary may to calibrate continuously monitoring instruments. Elsewhere (8) more extensive use of diffusion cells for the calibration of continuous monitoring colorimeters has been made. Diffusion cells have also been used in our laboratories and elsewhere (f9) to obtain approximate concentrations of odorants in very low concentration ranges. The use of diffusion cells has many advantages in terms of simplicity, reproducibility, and flexibility. The inacroscopic diffuqion eqnations should
be fairly exact. Equations based on simplified molecular models can be very useful in providing approximate diffusion rates when applied to molecules which do not fit the model used. Satisfactory diffusion rates can be calculated for systems which do fit the molecular model employed. Consequently, diffusion rates and diffusion coefficients can be determined using either completely empirical calibration or a theoretical calculation, n i t h a good degree of confidence in the method, if the limitations of each approach are understood. LITERATURE CITED
(1) Arnold, J. H., Znd. Eng. Chem. 22,
1091 11930’1. (2, Chambeis, F. S., Sherwood, T. K., Zbid., 29, 1415 (1937). (3) Cumminas. G. A . h4.. RlcLauehlin. E.. Ubbelohdc A. R.. J . ’Chem. SYc. 1955: 1141. (4) Cummings, G. -4. M., Ubbelohde, A. R.,Zbid., 1953,3751. (5) Fair, J. R., Lerner, B. J., A . Z. Ch. E . Journal 2, 13 (1956). (6) Fortuin, J. M. H., Anal. Chim. Acta 15, 521 (1956). ( 7 ) Gilliland, E. R., Znd. Eng. Chem. 26, 681 11934). (8) Gordon,’ C. Ii;, Rong-Woo, H., HelLvvig, H. I,., Techniques for the
Calibration of Atmospheric Analysers. Production of Dilute Gas Streams by ’Diffusion,”Air Pollution Control Association Meeting, Los Angeles, Calif., June 1959. (9) Hirschfelder, J. O., Bird, R. B., Spots, E. L., Chem. Reus. 44, 205 (1949). ( l o ) , Hirschfelder,lrJ. O., Curtiss, C. F., Bird, R. B., Molecular Theory of Gases and Liquids,’’ Wiley, New Torlr, 1954. (11) International Critical Tables, Vol. V, pp 62-3, AIcGraw-Hill, XeTv York, 1928. (12) Lee, C. Y., Wilke, C. R., Znd. Eng. Chem. 46, 2381 (1954). (13) McKelvey, J. PIT., Hoelscher, H. E., - ~ N A L .CHEM.29, 123 (1957). (14) Reid, R. C., Sherwood, T. K., “Properties of Gases and Liquids,]’ hIcGraw-Hill, Xem York, 1958, pp, 274-*5 ~~.
(15) Stefan, J., Fien. Ber. ( 2 ) 63, 63 (1871); 65, 323 (1872); 68,385 (1873); 98, 1418 (1889). (16) Trautz, hl., Ludwig, O., Ann. Physik. [ 5 ] 7,887 (1930). (17) Trautz, ll., Rluller, IT., Zbzd., [5] 22,329, 333 i1935). (18) Trautz, &I., Res, W.,Zbid., [ 5 ] 8 , 163 (1931). (19) Turk, A,, J . Agr. Food Chem. 1, 306 (1953). RECEIVED for review November 9, 1959. Accepted March 10, 1960. Division of Water, Sewage and Sanitation Chemistry, 136th Aleeting, ACS, Atlantic City, K.J., September 1959.
Separation and Characterization of Polynuclear Aromatic Hydrocarbons in Urban Air-Borne Particulates EUGENE SAWICKI, WALTER ELBERT, T. W. STANLEY, T. R. HAUSER, and F. T. FOX Air Pollution Engineering Research, Robert A. Tuft Sanitary Fngineering Center, Public Healfh Service, U. S. Departmenf of Healfh, Education, and Welfare, Cincinnafi 26, Ohio
b A simplfiied procedure is described for the characterization of polynuclear hydrocarbons in air-borne particulates. The method involves one pass through a chromatographic column and subsequent ultraviolet, visible, and fluorescence studies on the fractions thus obtained. The final step then involves a destructive method of analysis -e.g., spectral analysis in sulfuric acid-or a color test. The ultravioletvisible absorption spectra of analogous fractions obtained from different communities are closely similar. In the air-borne particulates of some 100 communities pyrene, fluoranthene, benzo[a]fluorene and/or benzo[b]fluorene, chrysene, benz[ a ]anthracene, benzo[ alpyrene, benzo[ e] pyrene, benzo[ klfluoranthene, perylene, benzo[ g,h,i]perylene, anthanthrene, and coronene are found consistently. 810
ANALYTICAL CHEMISTRY
A
SIMPLE standardized
analytical procedure is badly needed for the separation and identification of polynuclear aromatic hydrocarbons in the air-borne particulates of urban communities. A method was developed which involves one pass of the benzenesoluble fraction through a chromatographic column and then appropriate fluorometric studies and color tests dependent on the ultraviolet spectrum of each fraction. The pioneering work of Falk in column chromatographic and ultraviolet spectral studies of polynuclear hydrocarbons ( 1 ) and the fluorometric work of Van Duuren in cigarette tobacco tar (10 ) have been invaluable in application to air pollution studies. Extensive use has been made of the recently described activation and fluor t w t m p spectral techniques to identify a
fluorescent hydrocarbon in a mixture (e), This new analytical methodology is derived from the fact that in many instances it is possible to obtain the pure fluorescence spectrum of an aromatic compound in a mixture by determining the fluorescence spectrum of the mixture at an appropriate activating v-ave length maximum of the aromatic compound. The methods herein presented have been applied to samples from over 100 communities, with excellent reproducibility of analytical results. COLUMN CHROMATOGRAPHY
Procedure. T h e methods for t h e collection of air-borne particulates and the extraction of the benzenesoluble material from these particulates, as ne11 as t h e equipment and materials for column chromatography, have been described ( 7 ) .
301
tively. During this 2- to 3-hour operation the column mas protected from light, Fractions of 15 to 20 ml. were collected and then evaporated in a vacuum oven a t room temperature in the dark.
Figure 1 . Ultraviolet-visible bands useful in characterization of polynuclear aromatic hydrocarbons
241
'
I
I
1.2 254
W 0
Y
z
3 0.8 K
27
0
tn m
287
L
a
281 295 3ps"yo
0.4
I
250 Figure 2.
300 hmv
Discussion. Three factors t h a t affect t h e chromatography of a complex mixture are ( I ) t h e retardation volume-Le., t h e volume of eluent passing through t h e column per gram of adsorbent before t h e substance in question leaves t h e column, (2) t h e volume spread of t h e eluted substance-i.e., t h e volume of eluent in which the substance is found, and (3) t h e volume separation of t h e eluted substance from a second substance in a subsequent fraction. These factors can be affected by throe variabies: percentage of IT-ater in the alumina, percentage of ether in the pentane, and possible miscellaneous factors such as the composition a i d weight of the organic fraction. The retardation volume, the volunle spread, and the volume separation of aliphatic hydrocarbons and mono-, di-, tri-, and tetracyclic aromatic hydrocarbons are optimum in alumina containing 12 to 13% water for a pentane-ether eluent. For penta-, hexa-, and heptacyclic aromatic hydrocarbons alumina containing 14 to lS7, water works best. An increase in either the amount of water in the alumina or the percentage of ether in the eluent decreases the retardation volume. The effect of the composition of a complex mixture on the retardation volume and other factors is more difficult t o evaluate. For certainty of
' 340
350
Ultraviolet absorption spectrum of pyrene fraction in pentane
For the chromatographic lvork. Merck acid-rrashed aluminum oxide was washed with ether, dried, and heated in a n oven a t 130' C. for 30 hours. The alumina then contained 12% water (as determined b y neighing a sample, heating t o red heat for 10 minutes, cooling in a desiccator, and reweighing). Enough rvater was then added to the oven-dried alumina to give a final concentration of 13.7%. The mixture was mixed well and allowed t o stand for 12 hours in a stoppered container. One gram of the treated alumina was added to a small volume of the chloroform solution of 50 to 150 mg. of the
benzene-soluble fraction of an air particulate sample. The chloroform was evaporated so that the organic material n-as homogeneously dispersed in the alumina. The material is dispersed in alumina prior t o chromatography, because it is only slightly soluble in the primary eluting solvent. The mixture was then added to a 0.5 X 15 inch column which contained a l o m r layer of 9 grains of treated alumina and ail upper layer of 0.5 gram of silica gel, neither containing eluting solvent. The column was eluted with successive 100-ml. volumes of pentane containing 0, 3, 6, 9, and 12% of ether, respec-
230
260
290
320
hmv
Figure 3. Ultraviolet absorption spectra in pentane
____ _____
Rechromatographed pyrene fraction Pure pyrene
VOL. 32, NO. 7,JUNE 1960
81 1
Qperation an eluent of 100-ml. volumes of pentane containing 0, 3, 6, 9, and 12% ether is best when a new type of sample is initially investigated The hydrocarbons are eluted in the order: aliphatics, olefins, benzene derivatives] naphthalene derivatives, dibenzofuran fraction, anthracene fraction] pyrene fraction] benzofluorene fraction, chrysene fraction, benzopyrene fraction, benzoperylene fraction] and coronene fraction. For example, with alumina containing 13.7% water the pyrene fraction was found in the beginning of the 3% ether eluent; the chrysene fraction followed in the last part of the 3% ether eluent; the benzopyrene fraction appeared in the beginning of the 6% ether eluent. followed by the benzoperylene fraction in the start of the 9% ether eluent and the coronene fraction shortly afterward in the same 9% ether eluent. Although the relative location of the fractions was always the same, unknown variables sometimes caused the fractions t o elute sooner or later than expected. The fractions were fairly well separated] although test tubes containing the tail end of one fraction usually contained small amounts of the next fraction. Most fractions TTere found in three to six tubes. However, the benzoperylene and coronene fractions were each spread over six to ten tubes.
'
I
I
I
263
Figure 4. Ultraviolet absorption spectrum of benzofluorene fraction in pentane
1
I
w 2.0 0
z
a
1.5 0
cn a 1.0 m
CHARACTERIZATION OF POLYNUCLEAR AROMATIC HYDROCARBONS
Procedure. After evaporation in a vacuum oven at room temperature of t h e approximately 30 chromatographic fractions, t h e residue in each tube TTas dissolved in a small volume of pentane and then transferred t o a 3-ml. spectral cell of 1-em. light path. This procedure was repeated several times, so that the residue in the test tube was quantitatively transferred to the cell. The final volume was 3 nil. The ultraviolet-visible absorption spectrum of each solution was then determined from 220 to 450 mp.
All the important ultraviolet-visible absorption bands which are of value in characterizing the principal polynuclear hydrocarbons found in air-borne particulates arc summarized in Figure 1 These are the identifying bands found in the fractions obtained from airborne particulates collected all over the United Statrs. For each compound the relative heights of the bands are shown as obtained in the absorption spectra of the air fractions and of the pure sulistances. The hydrocarbons are arranged in the relative order in which they are found on the columne.g., the tricyclic fraction is eluted first and the coronene fraction last. From information deduced from these spectra, activation and fluorescence spectra in pentane were obtained at 812
ANALYTICAL CHEMISTRY
-
0.5
250
300
350
X,mlJ Figure
5.
- -.- - -..,
Ultraviolet absorption spectra in pentane
--
Pure chrysene
Chrysene fraction
I
38 I
Figure 6. Fluorescence spectra at activating wave length 264 mp in pentane
t
-.- - - - - - -
___
I I I,
350
I
400
LmP
Pure chrysene Chrysene fraction
appropriate fluorescence and activating n-ave lengths (6). The last step consists of a destructive method of analysise.g., absorption or fluorescence spectral analysis in sulfuric acid or a suitable color test. A typical procedure in the analysis of the eluent in one of the test tubes is the following. The ultraviolet-visible absorption spectrum of the eluted material in pentane showed the presence
.-
I
2 .o
1.5
(yJ \
/
/
W
0
z a m
8
1.0
cn
m
4
250
350
300 X,mlJ
Figure 7.
Ultraviolet absorption spectra in pentane
____._-__ Chrysene fraction -- Benz [a] anthracene
w 1.0 0
z a
m K
0 u)
m
a0.5
bmIJ Figure 8.
Ultraviolet absorption spectra in pentane
- - - - - - - -. --
Benzo [g,h,i]perylene Benzoperylene fraction
of bands a t 287, 305. 318, 33-1, and 358 nip. Examination of Figure 1 indicates that these bands are probably derived from pyrene and fluoranthene. The fluorescence spectra of the same solution determined a t activating wave lengths of 283 and 330 mp are identical to the fluorescence spectra of fluoranthene and pyrene, respectively. The activation spectrum of the same solution a t a fluorescence wave length of 445 mp
11-as identical to that of fluoranthene. This solution was then evaporated and dissolved in a few milliliters of sulfuric acid. The fluorescence spectrum a t an activation wave length of 351 m p and the activation spectrum a t a fluorescence wave length of 392 mp further indicated the presence of pyrene in the fraction. It was then concluded pyrene and fluoranthene mere present in this material.
Volatile Hydrocarbons. As airborne particulates are collected by pulling polluted air through a glass fiber filter for 24 hours, t h e more volatile aliphatic derivatives, as well as mono-, di-, and tricyclic aromatic compounds, are lost. Among these compounds are phenol, naphthalene, fluorene, dibenzofuran, anthracene, and phenanthrene. However, if the air-borne particulates are tarry or heavy, volatile materials are retained to some extent and will be found in the chromatographic cut before the pyrene fraction. Unless a sample is obtained very close to an industry that emits anthracene (A) and phenanthrene (Ph), only very small amounts of these two hydrocarbons are found in the particulates collected with a high volume sampler, and then only if the sample is particularly heavy. The evidence for the presence of these hydrocarbons is based on the presence of a very strong band a t 252 mp (A and Ph), a weak band a t 292 mp (Ph), and weak inflection points a t 275 (Ph), 281 (Ph), 338 (A), 354 (A), and 374 mp (A). This fraction gives a weak positive test for anthracene (a). Although fluorene could not be detected in this fraction through its ultraviolet or fluorescence spectra, a positive test for it n-as obtained with the thermochromic (4) and o-dinitrobenzene (9) tests. Pyrene Fraction. This fraction is eluted after t h e tricyclic hydrocarbons. A typical spectrum of t h e fraction is shown in Figure 2. T h e presence of pyrene is indicated by t h e 334-mp band in this curve. Further evidence for the presence of pyrene is based on the spectral similarity to pyrene of a purified fraction obtained through rechromatography by the same procedure (Figure 3). The fluorescence spectrum of the fraction in pentane shows the presence of the 382- and 392mp bands of pyrene. The fluorescence spectra in concentrated sulfuric acid of the fraction and of pure pyrene are identical. Unless otherwise stated, all spectra and tePts are determined on fractions obtained from one pass through the alumina column. Some cweptions are the nitration ( 7 ) , isatin (8),and 3nitro-4-dimethylaminobenzaldehyde(5') tests which were performed on the rcchromatographed pyrene fraction. The presence of fluoranthene is indicated by a sharp, fairly intense band at 287 mp and a somewhat broader and niore shalloiv band in the neighborhood of 358 mp in the ultraviolet absorption spcctrum of the pyrene fraction (Figure 2). The activating spectra obtained a t a fluorescence wave length of 445 mp, as !vel1 as the fluorescence spectra obtained a t an activating wave length of 283 mp of fluoranthene and the pyrene fraction, are identical. The evidence for the characterization of pyrene and VOL. 32, NO.
7,JUNE 1960
813
fluoranthene has been summarized in Table I. Benzofluorene Fraction. This mixture is eluted between the pyrene and chrysene fractions. A typical spec-
Table 1.
t r u m of the fraction indicates t h e presence of benzo [a]- and/or benzo[blfluorene (Figure 4). The fluorescence and activation spectra of the fraction resemble the analogous spectra
Evidence for Presence of Polynuclear Hydrocarbons in Various Fractions
Identification Method UV snectra Fl.a Lpectra, A.* X 330 F1.spectra, .4.X 351 A. spectra, F1. X 392
NDB teste Sitration test1 Isatin test0
Solvent
Common Bands, A,,,
M p
Pyrene Fraction and Pyrene Pentane See Fimre 2 Pentane 382, 352 HzSO,' 393, 410, 430id HzSO, 350, 369, 387, 282 703 625 685 Pyrene Fraction and Fluoranthene
UV spectra A. spectra, F1. X 445 F1. spectra, A. X 283
Pentane Pentane Pentane
236, 276, 281, 287, 341, 358 285, 340, 354, 32% 464, 445
Benzofluorene Fraction and Benzo [ a ]fluorene UV spectrah Pentane 254, 262, 273, 303, 316 F1. spectra, A. X 312 Pentane 340, 358 A . spectra,i F1. X 340 Pentane 317, 264, 340 A Thermochromic testi Yellow F? blue 725 o-Dinitrobenzene testk Green, A,,
L T spectra F1. spectra, A. X 264
Chrysene Fraction and Chrysene Pentane 257, 267, 320 Pentane 381, 362, 401 Chrysene Fraction and Benz [ a ]anthracene
Ul' spectra F1. spectra, A. X 284
UV spectra UV spectra F1. spectra, A. X F1. spectra, A. X .4.spectra, F1. X F1. soectra. -4.X SDB test '
Pentane Pentane
276, 287, 299, 315, 340, 358, 374, 382 382, 406, 430
Benzoperylene Fraction and Benzo [g,h,i]perylene Pentane 287, 299, 312, 329, 344, 361, 377, 382 HzSOa 405, 513 358 Pentane 419, 443, 405, 397 398 HzSOa 442, 421 442 HzSO, 398l 520 H8OA S o bands 770
UT' spectra F1. spectra, A. X 420 F1. spectra, A. X 563 A. spectra, F. X 430
Benzoperylene Fraction and Anthanthrene Pentane 429, 420, 406, 434i Pentane 430, 458, 488 HzSOa 581 422, 400, 304, 380, 361 Pentane Coronene Fraction and Coronene
UV spectra F1. spectra, A. X 300 F1. spectra, 8.X 310 S D B Test a
Pentane Pentane HzS04
See Figure 10 See Figure 11 442, 470, 498 725'"
F1. Fluorescence.
* A.
c
d
1
Activation. Concentrated sulfuric acid used in all cases. i. Inflection.
(3). (7). (8).
See Figure 4.
I n pure benzo[a]fluorene fine structure is found in 317-mp band at 288 and 303 mp. j
(4). (9).
318-mp band of benzo[g,h,i]perylene was missing in fraction. Also band at 683 mp in fraction.
814
ANALYTICAL CHEMISTRY
of benzo [a]- and benzo [hlfluorene. The fluorene thermochromic (4) and the o-dinitrobenzene (9) tests were positive for this fraction. The o-dinitrobenzene test has been shon-n to be specific for compounds containing the cyclopentadiene CH, group-eg., cyclopentadiene, indene, fluorene, benzofluorenes, etc. The evidence for the prcsence of benzo[a]- and/or benzo [blfluorene is summarized in Table I. Chrysene Fraction. T h e appearance of this fraction is signified by t h e gradual shift of the 255-, 262-, and 315-mp bands of the previous fraction into the 258-1 268-, and 320-mp bands of chrysene. A typical spectrum of the chrysene fraction is shown in Figure 5 . A comparison of the fluorescence spectrum of the fraction and pure chrysene gives further evidence for the characterization of chrysene in the fraction (Figure 6). Benz [alanthracene signifies its presence by the sharp intense band a t 287 mp and a somewhat broader and more shallow band a t 358 mp (Figure 7). I n fractions where there are fairly large amounts of benz [alanthracene, the weak 374- and 382-mp bands also show. Although the absorption spectrum of fluoranthene in a misture could be readily mistaken for benz [alanthracene, the fluorescence spectra in pentane easily differentiate the two hydrocarbons. At an activating wave length of 284 nip the fluorescence spectra of benz [alanthracene and the chrysene fraction are identical. The complete evidence for the characterization of chrysene and benz [alanthracene is summarized in Table I. Benzoperylene Fraction. This fraction is eluted after t h e benzopyrene fraction, which has been discussed ( 5 ) . il typical spectrum of the benzoperylene fraction is shoxn in Figure 8. This spectral envelope is common to all the communities thus far studied. The main method of differentiation of the benzoperylene fraction from the benzopyrene fraction is the absence of the 400- and 434-mp bands in the former, as well as the absence of fine structure in the 382-mp band. The fluorescence spectra of this fraction and benzo[g,h,i]perylene in pentane obtained a t an activating wave length of 358 mp are identical. Also the fluorescence spectra in concentrated sulfuric acid of these two are very closely identical. The absence of benzo[a]pyrene is shown by activation a t 520 mp in sulfuric acid; the 545-mp band of benzo[a]pyrene is absent in the resultant fluorescence spectrum. These data are summarized in Table I. The presence of bands a t 407, 420, and 428 mp with an inflection at 434 nip in the absorption spectrum of the fraction indicates the presence of
I
I
302
t
A
CORONENE
u
0
z 1.0 4
m
K
0 v)
m
a
0.5
250
‘350
300 hmlr
Figure 9. Activation spectra in pentane a t fluorescence wave length 430 mp
Figure 10.
Ultraviolet absorption spectra in pentane
--....-.-Pure coronene -- Coronene fraction
_._ .____. Anthanthrene
- Benzoperylene fraction
anthanthrene. The fluorescence spectra in pentane of the fraction and anthanthrene are identical. The fluorescence spectrum in sulfuric acid is different from that in pentane, but here again the fraction and anthanthrene give identical spectra. The activation spectra of the two are fairly similar (Figure 9). The data for the characterization of henzo [g,k,i]perylrme and anthanthrene are summarized in Table I. Coronene Fraction. This is t h e last definite fraction t o be eluted from t h e column. T h e most noticeable identifying feature in t h e spectrum of this fraction is t h e weak b u t dcfinite band at 338 nip. Usually two n-eaker bands a t 333 and 345 m p are also prcsent. A very intense band is found a t 302 mp with somewhat weaker bands a t 290 and 298 m p . These bands are a1.o found in coronene (Figure 10). The fluorescence spectrum of this fraction in pentane a t an activating wave length of 300 ml.c s h o w the presence of the three coronene bands (Figure 11). Moreover, in concentrated sulfuric acid a t an activating wave length of 327 mp) the fraction and c’oronene are spectrally identical (Figure 12). The evidence for the characterization of coronene is summarized in Table I LITERATURE CITED
(1) Falk, H. L., Steiner, P. E., Cancer Research 12, 30 (1952).
I
I ’
I
I
450
500
X,mP Figure 12. Fluorescence spectra in sulfuric acid a t aciivating wave length 3 2 7 m p X,mP
Figure 1 1 . Fluorescence spectra in pentane a t activating wave length 300
w
_.._ - ____ -__
Pure coronene Coronene fraction
( 2 ) Hauser, T. R., Chemist-Analyst 48, 86
(1909).
(3) Sawicki, E., Barry, R., Talanfa 2,
128 (1969).
(4) Sawicki, E., Elbert, W., ChemisfAnalyst 48, 68 (1959). ( 5 ) Sawicki, E., Elbert, W.,Stanley, T. W.,Hauser, T. R., Fox, F., Intern. J . A i r Pollution 2, 283 (1960).
.-.-_____ Pure coronene
--
Coronene fraction
(6) Saivicki, E., Hauser, T. R., Stanley, T. IT., Ibzd., 2, 2 i 3 (1960). ( 7 ) Sawicki, E., Miller, R. R., Ah IL. CHEM.30.109 11958). (8) Sawicki: E., btanlky, T. W., Hauser, T. R., Barry. R., I b d , 31, 1664 (1959). (9) Sawicki, E., Stanley, T. IT., Soe, J., Ibzd., 32, 816 (1960). (10) Van Duuren, B. I,., J . S a f l . C a n c ~ r Znst. 21, 623 (1968). RECEIVED for reviex Sovember 3, 1959. Accepted January 25, 1960.
VOL. 32, NO. 7, JUNE 1960
815
