Envlron. Scl. Technol. 1982, 16, 883-886
pleth Model”; report prepared for EPA by Santa Fe Research Corp., Mar 1981. (5) Carter, W. P. L.; Winer, A. M.; Pitts, J. N., Jr. Atmos. Environ. 1982, 16, 113-120. (6) Sakamaki, F.; Okuda, M.; Akimoto, H.; Yamazaki, H. En-
chemical Oxidants and Precursors”;EPA-450/2-77-021a, Nov 1977. U.S. EPA, “Proceduresfor Quantifying Relationshipsbe-
tween Photochemical Oxidants and Precursors: Supporting Documentation”;EPA-450/2-77-021b, Feb 1978. U S . EPA, “Guidelinefor Use of City-Specific EKMA in Preparing Ozone SIPS”;EPA-450/4-80-027 Mar 1981. Trijonis, J.; Mortimer, S. “Analysis of Historical Ozone Trends in the Los Angeles Region Using the EKMA Iso-
viron. Sci. Technol. 1982, 16, 45-52. Received for review January 29,1982. Revised manuscript received July 16, 1982. Accepted July 26 1982.
Gas Chromatography/Mass Spectrometry Identification of Organic Volatiles Contributing to Rendering Odors Herman R. Van Langenhove,” Fredy A. Van Wassenhove, Jos K. Coppin, Marc R. Van Acker, and Nlceas M. Schamp
Laboratory of Organic Chemistry, Faculty of Agricultural Sciences, State University of Gent, B-9000 Gent, Belgium
rn Organic compounds in rendering plant emissions, both in the factory building air and in neighborhood ambient air of the plant, were identified by a gas chromatography/mass spectrometry system using capillary columns. Adsorption on Tenax GC and selective solvent absorption of volatile organic acids were used as concentration techniques. The results indicated that 80% of the identified compounds, mainly aliphatic, aromatic, or halogenated hydrocarbons and terpenes, can be considered as ubiquitous volatiles, not contributing to the odor. Twenty-six volatiles including an amine, five sulfur compounds, eight volatile acids, one alcohol, and eleven aldehydes were identified as malodorants contributing to rendering odors, by matching each GC/MS analysis with the corresponding “odorogram”.
Introduction By collecting and processing fallen animals and slaughter offal, rendering plants contribute to the conservation of public health. Worthless offal is worked up into different valuable products: glue, bone- and fish-meal, and inedible grease and tallow. Unfortunately rendering activities involve the production of a wide variety of odorous volatiles ( l ) ,and in spite of the installation of odor abatement equipment, rendering activities often remain a source of public nuisance (2). Identification of the odorous compounds emitted by rendering plants is the first step toward an objective description of the odor problem and an essential need for the chemical evaluation of odor abatement technology. GC/MS analysis (3) permits separation of complex mixtures of organic compounds and structure identification of these substances even at 10-ng amounts. It is therefore the best available method for the identification of volatiles. Due to the sensitivity of the olfactory system, with thresholds as low as 0.1 ppb (vol/vol) ( 4 ) , concentration of the volatiles prior to identification remains necessary. Cryogenic trapping, solvent absorption, and adsorption on porous polymers are well-known concentration techniques. Cryogenic trapping has the disadvantage that considerable amounts of water, interfering with the GC/MS analysis, are collected. Two other concentration methods were used in order to get a broad spectrum analysis of the compounds present in rendering emissions. Adsorption on porous media followed by thermal desorption is a powerful, nonselective concentration technique. Activated charcoal (5) and synthetic polymers as Porapak QS (6)and Tenax GC (7, 8) have 0013-936X/82/0916-0883$01.25/0
been used in air pollution studies. Because of its hydrophobic character, its thermal stability up to 400 “C, and its inertness toward most of the pollutants (9),Tenax GC was the adsorbent of choice in this study. Highly polar organics, especially volatile organic acids, were not detected with the Tenax adsorption GC/MS method. Therefore, solvent absorption, a more selective concentration technique, was used to supply information about the presence of these compounds in rendering emissions. Because FID sensitivity and human olfactory sensitivity are not correlated, dominating peaks in the chromatograms do not necessarily represent volatiles important to the odor problem. Samples were analyzed by GC in order to evaluate whether or not compounds present in the samples contribute to rendering odors. The instrument was provided with a splitter, which conducts parts of the column eluate to the open air. An analyst, observing the FID signal, sniffed at the eluate and wrote down any observed odor character. This method (10) does not give information about odor thresholds or intensity-concentration relationships of the compounds. It is a method to select malodorants out of the complex mixture of volatile organics present in the samples. Results of GC/MS identification of volatiles sampled by either adsorption or selective solvent absorption from rendering emissions are reported in this paper. Compounds that contribute to rendering odors (according to the “odorogram” method) are indicated.
Experimental Section Sampling Sites. Sampling was performed in a Belgian rendering plant with an annual capacity of 10000 t of raw material. In this plant materials are processed by cooking under vacuum. Vapors released during the cooking process pass consecutively through a grease trap, a surface condenser, and two water scrubbers before they are emitted to the atmosphere. Samples were taken in the factory building, at the outlet of the last scrubber, and in the neighborhood of the plant. Sampling Procedures. Tenax GC, used in adsorption tubes, was purified by extracting with acetone for 6 h in a Soxhlet apparatus. The moist polymer was transferred to a Rotavap, and excess solvent was evaporated. Glass tubes (0.7 cm i.d. X 15 cm long) were filled with 1 g of Tenax GC and then conditioned overnight at 240 “C under a helium flow (10 mL/min). After cooling, the tubes were closed and kept closed with glass stoppers. The air sampling flow rate was set at 0.5 L/min with a rotameter
0 1982 American Chemical Society
Environ. Scl. Technol., Vol. 16, No. 12, 1982 883
Table I. Organic Volatiles Identified b y the Tenax Adsorption GC/MS Methoda present .U
1'1
sensory evaluation odor character
present in
___
sensory evaluation odor character
compound Ipb a b c compound Ipb a b c dichlorodifluoromethane X chlorobenzene 858 x x 2-methylpropane X ethylbenzene 865 x x x 1-butene x x x dimethylthiophene X 869 butane 400 x x x 814 x x x m,p-xylene methanethiold 410 x x putrid, bad nonene 891 x x trimethylamined 432 x x x fishy, ammonia styrene 899 x x 2-methylbutane 462 x nonane 900 x x x trichlorofluoromethane o-xylene 478 x x x 901 x x x pentene heptanald 484 x x 910 x x x fatty a-thujene pentane 929 x 500 x x x 2-propanone propylcyclohexane 935 x 509 x x x acetone methyl propyl disulfideC 939 x putrid diethylether 514 x x ether or-pinene dimethyl sulfided 940 x x x fir 520 x x x putrid terpene (mol wt 136) 954 x fresh propanalC 532 x x x sharp camphene 951 x x carbon disulfide x 534 x benzaldehyde X 96 2 dichloromethane 534 x x sweet, ethereal propylbenzene isomer 969 x x x 2,3-dimethylbutane 557 x methylethylbenzene isomer 970 x x x 2-methylpropanaF 563 x x x malty methylethylbenzene isomer 976 x x x 2-methylpentane 561 x x x sabinene 981 x 3-methylpentane 580 x x x dimethyl trisulfided 982 x putrid hexene 590 x x p-pinene 985 x x x hexane 600 x x x 2-pentylfuran 996 x x x butanald 605 x malty, burnt 1000 x x x 2-butanone decane 610 x solvent 1003 x x x trichloromethane trimethylbenzene isomer 621 x x ethereal methylcyclopentane 1012 x 628 x x x or-phellandrene ethyl acetate 1014 x x x fatty, oily octanald 634 x fruity A -carene tetrahydrofuran x 1017 x x 637 x trichloroethane butylbenzene isomer 643 x x sweet 1024 x x 3-methylb~tanal~ butylbenzene isomer 659 x x x buttery 1033 x x cyclohexane a-dichlorobenzene 665 x x 1035 x x x sanitary thiophene X tetramethylbenzene 665 1040 x x x tetrachloromethane limonene 1042 x x x lemon 667 x x benzene m-dichloro benzene 661 x x x 1051 x x x sanitary 2-methylbutanaF 669 x x x aldehydic tetramethylbenzene isomer 1058 x x x 3-methylhexane 674 x x terpene (mol wt 136) 1095 x 2,2,4-trimethylpentane x 686 x undecane 1100 x x x heptene 690 x x nonanalC 1115 x x x fatty, oily heptane 700 x x x tetramethylbenzene isomer 1133 x x x pentanald 704 x x x fatty, pungent dodecane 1200 x x x trichloroethylene 707 x x x naphthalene 1208 x x x naphthalene methylcyclohexane 725 x x x tridecane 1300 x x 1 5 1 x x x putrid decanalC 1317 x citrus fruit dimethyl disulfided toluene 771 x x x (skin) methylnaphthalene octene 790 x x 1323 x x met hylthiophene terpene (mol wt 1 3 6 ) X 1393 x 792 tetradecane 1400 x x octane 800 x x terpene (mol wt 1 3 6 ) hexanald 1446 x 807 x x x fatty, green pentadecene 1492 x x pent anold 810 x 1500 x x pentadecane tetrachloroethylene 813 x x x octadiene 824 x a Key: a, scrubber outlet samples; b, air sampled in factory buildings; c, ambient air samples. Ip, Kovats index o n SE 52. Malodorants not previously identified in rendering odors. Malodorants previously identified by others (23, 2 4 ) .
(Matheson 603) previously calibrated with a soap film bubble meter. Sampling times were 30 min in the factory building and for ambient air samples and 10 min for samples at the scrubber outlet. Organic acids were sampled by absorption in 10 mL of 0.5 NaOH in Pavelka traps (11). Sampling was performed at a flow rate of 1L/min during a 45-min period. Samples were evaporated to dryness; the residues were redissolved in 1mL of distilled water. After saturation with NaCl and acidification with hydrogen chloride to pH 1, the water phase was extracted with 1mL of ether (Merck). Aliquots of the organic phase were analyzed by GC/MS. Instrumentation. GC/MS instruments used for identification included a Varian 2700 gas chromatography with FID and an MAT 112 mass spectrometer. For the analysis of adsorption samples, a desorption oven was 884
Envlron. Sci. Technol., Vol. 16, No. 12, 1982
constructed. The normal GC injector was replaced by a six-way valve provided with a cold trap. During thermal desorption, an adsorption tube was heated from 25 to 220 "C over a period of 15 min and held at 220 "C for 30 min while helium was passed through it in order to transport desorbed volatiles to the cold trap. The carrier gas was connected directly to the column. When injecting, the valve is switched so that the currier gas first flows through the cold trap before going into the column. Volatiles were flash-evaporatedby quickly heating the cold trap by means of a high-intensity halogen floodlight. The helium carrier gas flow rate was 4 mL/min. The temperatures of injector and detector were held at 240 "C. The 100 m X 0.5 mm i.d. glass capillary column coated with SE52 was temperature programmed from 10 to 220 "C at 1 "C/min. Absorption samples were directly injected on a 25 m X 0.5
mm i.d. FFAP glass capillary column with temperature programming from 50 to 150 OC at 4 "C/min. Columns were obtained from Alltech Europe. According to the distributor, columns were static coated. Liquid-phase loadings of the SE52 and FFAP columns were 6 and 2 mg/mL, respectively. A splitter was installed between the column and the FID detector to divert about of the effluent to the mass spectrometer source via a platinum capillary. Mass spectrometer conditions were as follows: temperature of the platinum capillary, 250 "C; ionizing energy, 70 eV; source pressure, lo6 torr; scan range, 10-250 m/e; scan speed, 2.5 s/scan. For every FID peak detected, the mass spectrometer was scanned manually. The interpretation of mass spectra was performed with the aid of reference books (12, 13) and original papers on mass spectra of organics (14,15). The chemical identification and the Kovats index of all malodorants were checked by GC/MS analyses of authentic samples. Blank analyses showed that, in the conditions as described above, Tenax GC tubes were well conditioned, that the cold trap GC/MS system was not contaminated, and that contamination of adsorption tubes during storage did not occur. Tenax adsorption samples were used for the olfactory analyses. Samples were analyzed on a Varian 2700 GC with FID, with the same columns and operational conditions as during GC/MS analyses. However, a splitter constructed in the FID detector oven conducted of the column eluate to the FID detector. The rest went to a warmed outlet were an analyst evaluated the odor character of the eluting compounds. Within the scope of other research work, dynamic olfactometry was carried out in our lab, with a panel of 10 persons. Because the aim of the work described in this paper was a broad spectrum analysis of rendering malodorants, panelists were selected who showed high olfactory sensitivity and no olfactory anomalies to perform the "odorogram" analyses.
Results and Discussion Compounds identified with the Tenax adsorption GC/MS method are summarized in Table I. The presence of compounds in air emitted at the scrubber outlet (a), in factory building air (b), or in ambient air in the neighborhood of the plant ( c ) is indicated. The last column in Table I states results of the sensory evaluation of the compounds. Table I is a summary of all identified compounds, which means that not every compound was present in each sample. Comparing these results with previous studies (9,16-22) on ambient air volatiles shows that 80% of the compounds can be considered as ubiquitous. Most of these compounds are aliphatic or aromatic hydrocarbons and terpenes. Propyl and higher alkylbenzene derivatives and compounds recognized as monoterpenes by M+ 136 and intense peaks at m / e 93, 121, 79, and 77 were only partially identified by their mass spectrum. Mass spectra reveal the general chemical nature of these compounds, while individual substances were recognized by their Kovats index. From the non-hydrocarbon compounds, 2-butanone, thiophene, methylthiophene, dimethylthiophene, and benzaldehyde were present in ambient air samples alone. Two chlorofluoromethanes and nine chlorinated hydrocarbons were identified. These volatiles were not considered as specific for rendering emissions because different authors (16-22) have already identified these compounds in ambient air. Acetone, diethyl ether, carbon disulfide, tetrahydrofuran, and ethyl acetate were not retained as rendering malodorants because these compounds were not detected during sensory analysis, because they have al-
Table 11. Compounds Identified b y Selective Solvent Absorption GC/MS Methoda Dresent in compound diethyl ether (solvent) acetic acid propionic acid isobutyric acid butyric acid isovaleric acid valeric acid isocaproic acid caproic acid ionolb
a
b
C
X
X X
X
X X X X
X X X
X X X X X X
X X
X X
a Key: a, scrubber outlet samples; b, air sampled in the factory buildings; c , ambient air samples. Present in diethylether.
ready been identified in ambient air (17,18,20) or because both of these reasons. All the other compounds were identified in scrubber outlet emissions or in factory building air and were recognized as malodorants during the sensory evaluation of the samples. Among these the malodorants that have already been identified in rendering emissions are trimethylamine, butanal, pentanal, hexanal, heptanal, dimethyl sulfide, dimethyl disulfide (23, 24), pentanol (23), octanal, methanethiol, and dimethyl trisulfide (24). Propanal, nonanal, decanal, 2-methylpropanal, 3-methylbutanal, 2-methylbutanal, and methylpropyl disulfide have not been identified before as rendering malodorants. In older studies (25,26) nuisance caused by rendering plants was attributed to amines, aldehydes, sulfur compounds, and fatty acids. However, no individual compounds were identified. Compounds of all these classes except fatty acids were identified with the Tenax absorption GC/MS method. The reason for this lack is that the great difference in polarity between acids and SE52 stationary phase leads to broad asymmetrical acid peaks. Due to spreading and interference with other compounds detection of organic acids with the Tenax GC method became very difficult. Therefore, air was sampled by selective solvent absorption (27), and acids were identified by GC/MS on a FFAP stationary phase. As shown in Table 11, linear and is0 acids from acetic acid up to caproic acid were detected in scrubber outlet samples (a) and in factory building air (b). In ambient air in the neighborhood of the plant is0 acids were not detected. Out of the eight organic acids identified in the different samples, butyric acid, valeric acid, and caproic acid have already been reported in rendering emissions (2).
Conclusion GC/MS analysis of compounds sampled by either adsorption on Tenax GC or selective solvent absorption from rendering scrubber emissions, factory building air, and air in the neighborhood of the plant resulted in the identification of about 110 organic volatiles. By sensorial evaluation of GC eluates of the samples and by comparison of results with existing information on volatiles generally present in ambient air, 26 compounds contributing to rendering odors were selected. From these, propanal, nonanal, decanal, 2-methylpropanal, 3-methylbutanol, 2-methylbutanal, methylpropyl disulfide, propionic acid, isovaleric acid, and isocaproic acid have not been identified before in rendering emissions. Envlron. Sci. Technol., Vol. 16, No. 12, 1982 885
Literature Cited (1) Bethea, R. M.; Murthy, B. N.; Carey, D. F. Environ. Sei. Technol. 1973, 7, 504-510. (2) Yocom, J. E.; Duffee, R. A. Chem. Eng. 1970, 77,160-168. (3) Keith, L. H. J. Chromatogr. Sci. 1979, 17, 48-54. (4) Fazzalari, F. A., Ed. “Compilation of Odor and Taste
Threshold Value Data”; ASTM Data Series DS 48A, ASTM, 1916 Race Street, Philadelphia, PA 19103, 1978. (5) Grob, K.; Grob, G. J. Chromatogr. 1971,62, 1-13. ( 6 ) Smith, M. S.; Francis, A. J.; Duxbury, J. M. Environ. Sci.
Technol. 1977,11, 51-55. (7) Brooks, B.; Jickels, S. M. J. Assoc. Public Anal. 1978, 16, 101-115. (8) Sydor, R.; Pietrzyk, D. J. Anal. Chem. 1978,50,1842-1847. (9) Raymond, A,; Guiochon, G. Environ. Sei. Technol. 1974, 8, 143-148. (10) “Odors from Stationary and Mobile Sources”; Board on
(11) (12) (13) (14) (15)
Toxicology and Environmental Health, National Research Council, National Academy of Sciences: Washington D.C., 1979; Chapter 4, pp 5-8. Pavelka, F. Mikrochem. Acta 1964, 9, 1121-1125. “Eight Peak Index of Mass Spectra” Mass Spectrometry Data Centre, AWRE, Aldermaston, Reading, RG7 4PR, UIC., 1974, Vol 1-111. Stenhagen, E., Abrahamsson, S., McLafferty, F. W., Eds. “Atlas of Mass Spectral Data”; Interscience Publishers: New York, 1969; Vol. I, 11. Levy, E. J.; Stahl, W. A. Anal. Chem. 1961, 33, 707-723. Gilpin, J. A,; McLafferty, F. W. Anal. Chem. 1957, 27,
(16) Bertsch, W.; Chang, R. C.; Zlatkis, A. J. Chromatogr.Sci. 1974,12, 175-182. (17) Pelizzari, E. D.; Bunch, J. E.; Berkeley, R. E.; McRae, J. Anal. Chem. 1976,48,803-807. (18) Ioffee, B. V.; Isidorov, V. A.; Zenkevich, I. G. J. Chromatogr. 1977, 142, 787-795. (19) Ciccioli, P.; Bertoni, G.; Brancaleoni, E.; Fratarcangeli, R.; Bruner, F. J. Chromatogr. 1976, 126, 757-770. (20) Halzer, G.; Shanfield, H.; Zlatkis, A.; Bertsch, W.; Juarez, P.; Mayfield, H.; Liebich, H. M. J.Chromatogr. 1977,142, 755-764. (21) Russell, J. W.; Shadoff, L. A. J. Chromatogr. 1977, 134, 375-384. (22) Louw, C. W.; Richards, J. F.; Faure, P. K. Atmos. Environ. 1977, 11, 703-717. (23) Doty, D. M.; Snow, R. H. “Investigation of Odor Control in the Rendering Industry”; EPA-R2-72-088, Oct 1972. (24) Bailay, J. C. In “Odour Control. A Concise Guide”; Warren
Spring Laboratory, Valentin, F. H. H., North, A. A., Eds.; Hertsfordshire, 1980. (25) Teller, A. J. J.Air. Pollut. Control Assoc. 1962,13,148-149. (26) Walsh, R. T. J. Air. Pollut. Control Assoc. 1967,17,94-97. (27) Maarse, H.; Schaefer, J. In “Analysis of Food and Beverages”; Charalambous, G., Ed.; Academic Press: New York, 1978; p 17-35.
Received for review December 7, 1981. Accepted July 9,1982.
990-994.
ADDITIONS AND CORRECTIONS 1982, Volume 16
James G . Seelye, Robert J. Hesselberg,* and Michael J. Mac: Accumulation by Fish of Contaminants Released from Dredged Sediments. Page 462. Table IV is to be replaced by the following: Table IV. Mean Concentration (pg/g of Dry Sediments) of Elements and Organic Contaminants in Saginaw Bay Sediments (One Standard Error in Parentheses) detection contaminant limit
As Br Na Se Hg Cr cs Ni Rb Fe Zn Sb PCBs (1248) total DDT (D.D’-DDT+ &?-DDD) 1977.
886
1978.
Environ. Scl. Technol., Vol. 16, No. 12, 1982
expt la
expt 2 and 3&
0.45 7.08 (0.253) 9.08 (0.290) 0.50 13.95 (0.159) 14.85 (0.160) 10.00 5118.5 (58.14) 7074.9 (55.13) 0.50 1.13 (0.011) 4.44 (0.319) 0.20 0.52 (0.004) 1.47 (0.012) 0.45 33.16 (0.246) 37.84 (1.343) 0.04 1.96 (0.027) 2.05 (0.023) 4.00 40.21 (3.678) 60.39 (7.466) 0.50 46.82 (1.094) 77.80 (2.855) 12.00 16687.4 (75.25) 17768.7 (135.66) 1.00 136.68 (2.449) 219.88 (4.971) 0.01 0.29 (0.007) 0.90 (0.204) 0.01 1.35 (0.062) 1.19 (0.042) 0.003 0.02 (0.001 j 0.02 (o.oo2j
