Characterization of Crude, Semirefined and Refined Oils by Gas-Liquid Chromatography M . E. Garza, Jr.’ Region V I , Environmental Protection Agency, Houston, Tex. 77036
Jerald Muth Region I X , Water Quality Office, Environmental Protection Agency, San Francisco, Calif. 941 11
A method is described for characterization of oils that is simple, requires comparatively little time and utilizes instrumentation and techniques that are available in most laboratories. Chromatograms are shown (combination flame ionization and flame photometric responses) of crude oils from different sources, artificially “weathered” samples of crude oils, samples of oil spills, and samples of lubricating oils removed from internal combustion engines. It is shown that crude oil may be laboratory “weathered” and will duplicate the chromatograms of materials extracted from oil spill samples. Furthermore, lubricating and fuel oils can be identified as to source by this procedure. The analysis of an oil sample, exclusive of artificial “weathering” and separation of some of its component fractions, can be accomplished in about 2 hr.
The ability to “fingerprint” and pinpoint the source of oil spilled in a river, harbor, or on a beach is essential to the control of water pollution. Oil from spills which occur many days prior to their discovery still retains many of its characteristics which the analyst is able to identify. The present methods are time consuming (requiring days instead of hours) and complicated, involving techniques of metals analysis (Gamble and Jones, 1955), determination of sulfur content (ASTM, 1962), infrared absorption techniques (Kawahara, 1969), and others. With the proposed method, in most oil spills comparison of chromatograms-of the oil spilled and of oil from the suspected sources-is sufficient to determine the source. Only 4 or 5 hr are required to make identification. When gas-liquid chromatographic separation and dual response (flame ionization for hydrocarbons and flame photometric for sulfur-containing compounds) are employed, the identification of crude, semirefined, and refined oil is greatly si mplifed. The response of the flame photometric detector to sulfur-containing hydrocarbons depends on the concentration of individual compounds and separation on the gas chrom atographic column. All oils contain different and varying amounts of sulfur-containing hydrocarbons; therefore, the chromatograms obtained with the 394-mp filter vary in retention time, relative intensity, and peak configuration. This method utilizes these differences for the identification of oils. Brody and Chaney (1966), employing a flame photometric detector using the 394-mp filter, noted differences of sulfur content and sulfur-containing compounds in different brands and grades of gasolines. Bowman and Beroza (1966 and 1967), Getz (1967), and others have successfully determined thiophosphate pesticides qualitatively and quantitatively, employing the flame photometric detector with a 526-mp filter.
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Figure 1. Crude oil, field A , temperature programmed 15*/min, 60-250°C, 394 mp filter Column, 3% SE-30, 4 mm X 3 m recorder speed, 1/2 in. /mtn
Figure 2. Crude oil, field 6 ,temperature programmed 15”/min,
6O-25O0C, 394 mp filter l To
whom correspondence should be addressed.
Column 3% SE-30, 4 rnm X 2 m recorder speed, ’12 in /min
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Results and Discussion For all figures, the following conditions are true: detector, Melpar: carrier, Nz, 80 cc/min; air, 100 cc/min; Hz, 150 cc/min; 0 2 , 20 cc/min. The different columns and recorder speeds are noted under each caption. The flame ionization, flame photometric responses of
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crude oils from two different oil fields are shown in Figures 1 and 2. These crude oils on examination exhibit differences in relative intensities, retention time (rt) and peak configuration on both types of detectors. Starting with the first significant peak at rt of 6 min, differences and similarities are noted throughout the chro-
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Co. A diesel fuel, temperature programmed 15"/min, 6O-25O0C, 394 m p filter
Figure 3.
Column , 3% SE-30. 4 mm X 2 m recorder speed,
l4
in./rnin
Figure 4.
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la
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Diesel fuel Co. E , temperature programmed 15'/min,
6O-25O0C, 394 rnF filter Column 3% SE-30, 4 mm X 2 m recorder speed
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min /min
I , ? , ? , , , , , , , , 12
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Crankcase oil from automobile in authors' parking lot, temperature programmed 15'/min 6O-25O0C, 394 mF filter
Figure 5.
Column, 3% SE-30,4 mrn X 2 m recorder speed, '/4 in./min
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Crankcase oil in Figure 5, temperature programmed 15"/min 6O-25O0C, 526 rnp filter
Figure 6.
Column 3% SE-30 4 mm X 2 m recorder speed
/4
in min
matograms. In general, these differences or similarities are sufficient to denote different or identical crude oils. When the differences are not great enough to be obvious, intensity ratios of significant corresponding peaks may be used-i.e., the intensity ratios of the major peaks in the chromatograms at approximately rt of 12 min to the corresponding peaks at rt of 6Yz min, are shown in Figure 1, 0.48 and Figure 2, 0.36. The intensity ratios of the two major peaks to the corresponding peaks at rt of 7Y2 min are Figure 1, 0.60 and Figure 2, 0.45. The intensity ratio of the major peaks to all other significant peaks in the chromatograms may be calculated to establish identity. The techniques of ratioing the intensity of the major peaks and all other significant peaks in the chromatograms may also be employed in the chromatograms of the
aromatic fractions (Figures 10 and 11) and the aliphatic fractions (Figures 12 and 13) of the samples. The same differences, Figures 3 and 4, were noted for semirefined oils processed by different companies. Weathered oil spills present the greatest analytical problems in identification and source tracing by existing methods. The present method eliminates most of these problems by artificial laboratory "weathering" and direct visual examination of the weathered spill and the suspected source. In weathered oil spills and unweathered suspected source samples, the flame photometric (394-mp) responses are used in a screening process. Figure 7 (refuge oil spill) and Figure 8 (refinery crude oil) are good examples of the flame ionization, flame photometric responses of weathered and unweathered samples.' Figure 8 exhibits a large
Figure 7. Refuge oil spill sample, temperature, programmed 10"/min, 60-300" C, 394 m p filter Column, 3% OV-1, 2 mm X 3 1 m recorder speed,
'12
in /min
v
k
J Figure 8.
Refinery crude oil sample, temperature programmed 10"/min, 60-300°C, 394 m p filter Column, 3% OV-1, 2 mm X 3 1 m recorder speed,
l/2
in /min
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number of low-boiling hydrocarbons on the flame ionization response, while the refuge oil spill sample of Figure 7 does not. The flame photometric response for both samples are identical, indicating that the refinery could be the source of the refuge oil spill. The chromatograms of the laboratory "weathered" refinery crude, Figure 9 is nearly a duplicate of Figure 7 , refuge oil spill, further indicating that the refinery was the source of the refuge oil spill. Chromatograms of the aliphatic and aromatic fractions (see experimental section) of the refuge oil spill and the refinery crude oil samples supplies further evidence that the refinery was the source of the oil spill. The procedure employed on the refinery crude and the refuge oil spill samples yielded three different flame ionization responses and two different flame photometric responses of each
sample for direct comparison (all sulfur-containing hydrocarbons noted were aromatic in nature). Should additional information for direct comparison be desired, the 394-mp filter may be replaced with a 526-mp filter, a different flame photometric response is obtained (Figures 5 and 6). The flame photometric and flame ionization responses of a variety of oils collected from 25 oil fields and other sources were examined to determine if gas-liquid chromatographic column separation and flame ionization and flame photometric responses could be used to distinguish differences in oils with reproducible results. Forty-nine different oils and oils from six spills were examined: In addition, two diesel fuels (different companies), six waste crankcase oils (brands unknown), 33 crude oils (25 different oil fields), one grease (outboard lower unit grease),
Figure 9. Laboratory-weathered refinery crude, temperature programmed lO"/min, 60-3OO0C,394 m k filter Column, 3% OV-1, 2 rnm X 3.1 m recorder speed, 'h in./rnin
Figure 10. Aromatic fraction of oil spill sample, temperature programmed 10"/min, 6O-25O0C, 394 mw filter Column 3% OV-1, 2 mm X 3 1 m recorder speed '/2
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/min
and 7 Bunker C oils were examined. This procedure identifies oil spill sources by direct comparison of flame ionization responses and 394 mp and 526 mp filter responses. The weathering effect on oil spills by wind, water, sunlight, temperature, and other environmental factors has to be considered in order to apply this method to oil pollution problems. One significant effect of oil spill weathering is the rapid evaporation and loss of low-boiling hydrocarbon fractions. Six oil spills in the Southwest, in fresh- and saltwater, during the years of 1968 through 1970, offered opportunities to test this method in its entirety and to determine its effectiveness. The oil spill samples collected were in varied forms-as slicks, emulsions, and thick viscous layers,
affording a full range of sample conditions and weathering. The Game Refuge pollution sample (Figure 7) was collected from the spill area. It was prepared for analysis as described in the experimental section. The resulting chromatograms of the flame ionization and flame photometric (394 mp) responses eliminated all other suspected sources and pinpointed the refinery crude (Figure 8) as the source of the spill in the Game Refuge. A portion of the refinery sample (Figure 8) was "weathered" as described in the experimental section. The resulting chromatogram (Figure 9) is identical in peak retention time, relative intensities, and configuration to the oil spill sample (Figure 7).
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Figure 11. Aromatic fraction, laboratory-weathered
refinery crude, temperature programmed 1 0 " / m i n , 60-3OO0C, 394 m p filter
Column 3% OV-1 2 mm X 3 1 m recorder speed
Figure 12.
In min
Aliphatic fraction of oil spill sample, temperature programmed lO"/min, 60-3OO0C, 394 m p filter Column, 3% OV-1, 2 mm X 3 1 m recorder speed, '12 In /min
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As a further confirmation, the "weathered" sample and the oil spill sample were separated into aliphatic and aromatic fractions (see Experimental Section) and the corresponding fractions compared. (Figures 10-13). Again the fractions are identical. Experimental Examination of all oils was performed on a Micro-Tek MT-220 gas chromatograph equipped with FPD detectors. T h e gas chromatographic columns employed were a glass "U" type 2 m x 4 mm i.d., packed with 3% SE-30 on 60/80 -mesh Chromosorb W, and a stainless steel coiled
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"U" type 3.1 m x 2 'pm i.d., packed with 3% OV-1 on 801 100 Chromosorb W, AW, DMCS High Performance. The operating conditions were as follows: column temperature programmed from 60-250°C at 15"/min and 60-300°C a t lO"/min. The detector temperatures were 170" and 220°C; the injection port temperatures were 225" and 300°C. The gas flows were: nitrogen carrier gas 80 ml/min, hydrogen flow 150 and 200 ml/min, oxygen flow 20 ml/min, and air flow of 100 and 120 ml/min. Electrometer sensitivities were: FID, 4 x 10-lO through 64 X amp full scale; FPD, 3 . 2 x 10-8 amp full scale.
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Figure 13. Aliphatic fraction, laboratory-weathered refinery crude , temperature programmed 10"/min, 60-3OO0C,m p filter COlUmn 3% OV-1 2 mm X 3 1 rn recorder speed
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60-250'
Column 3% SE-30. 4 m m X 2 m recorder speed. 'I4 in Jmin
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diesel fuel, temperature programmed 15'/min, C,394 m p filter
Figure 14. Co. A
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In min
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Diesel fuel extracted from Mississippi River water, temperature programmed 15"/rnin 6O-25O0C,394 m p filter Figure 15.
Column 3% SE-30 4 m m X 2
rn recorder speed
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The recorder used was a Westronics MT-22, dual pen having 1mV full-scale sensitivity. Samples of oil, each 100 pl, were diluted with n-hexane in ratios of 1 to 25 and 1 to 50. The amounts injected for examination ranged from 1- 5 pl. Portions (100 pl.) of the pollution and suspected source samples were cleaned and dried by dissolving them in nhexane and passing them through a 1-in. column of anhydrous sodium sulfate. The volumes of each were reduced to 5 ml on a water bath a t 70°C, and aliquots ranging from 1-5 p1. were injected into the gas chromatograph. Water Partitioning. Three 1-ml samples were obtained from each “standard” oil sample and added to 800 ml of Mississippi River water in clean 1-qt glass jars. The samples and 800 ml of Mississippi River water blank were stirred for 1 hr with the aid of 2-in. Teflon-coated magnetic stirring bars and magnetic stir-jacks. The samples and the Mississippi River water blank were then extracted with 30 ml of n-hexane and dried on a 5-cm, column of anhydrous sodium sulfate. “Standards” of each oil were prepared by diluting 100 pl. of the oil to a volume of 5 ml with n-hexane. The n-hexane extracts of the samples and Mississippi River water blank were reduced to a volume of 25 ml on a water bath a t 70°C and aliquots, ranging from 1-5 pl., of the extracted samples, blank and corresponding “standard,” were injected for analysis. The gas chromatographic responses were compared for reproducibility (Figures 14 and 15). Weathering. One gram of the refinery sample (Figure 8) was laboratory “weathered” by placing the sample in a water bath a t 70°C for 4 hr to remove the more volatile components and reduce the sample 25% by weight by evaporation. A 100-p1. portion of the “weathered” sample was diluted to a volume of 5 ml with n-hexane and 5 pl. were injected into the gas chromatograph for analysis.
Aliphatic, Aromatic Separation. Another portion of the “weathered” refinery crude oil sample and a similar amount of the oil spill sample were each dissolved in 5 ml of ethyl ether and transferred to columns containing 2.5-cm layers of silica gel. The ethyl ether was evaporated’ from the column with the aid of a small reverse flow of prepurified nitrogen gas. The columns were eluted with 75 ml of isooctane, then with 75 ml of benzene, collecting the eluates separately. The two eluates collected from each sample contained the aliphatic and aromatic fractions, respectively. The eluates were reduced to a volume of 25 ml on a water bath and 5 pl. of each eluate were injected into the gas chromatograph for analysis. The use of a proprietary product is for information and does not necessarily imply endorsement of the product by the U S . Environmental Protection Agency.
Acknowledgments The authors thank Micro Tek Instrument Corp., a subsidiary of Tracor, Inc., for the use of a Micro Tek M T 220 gas chromatograph equipped with a Melpar detector. Literature Cited Amer. SOC.Test. Mater., Philadelphia, Pa., ASTM Designation D, 129-62 (1962). Bowman, M . C., Beroza, Morton, A . O.A.C., 49, 1154 (1966). Bowman, M . C., Beroza, Morton, ibid., 50,940 (1967). Breidenbach. A. W.. “The Identification and Measurement of Chlorinated Hydrocarbon Pesticides in Surfa\ce Waters,” USDI, FWPCA (1966). Brodv. Sam S.. Chanev. John E.. Research Div.. Meloar Inc.. Fails C h u k h , Va. “ Gamble. L. W., Jones. W. H.,Anal. C h e m , 27.1456-9 (19551. Getz, Melvin E., Gas Chromatog., 5 , 377 (1967). Kawahara, F . K., Enuiron. Sei. Technol., 3, 150-3 (1969). Received for reuieu, December 23, 1971. Resubmitted October 26, 1973. Accepted November 7, 1973.
Migration and Redistribution of Zinc and Cadmium in Marine Estuarine System Charles W. Holmes,’ Elizabeth Ann Slade, and C. J. McLerran U.S. Geological Survey, Corpus Christi,
Tex.7841 1
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A survey of trace-element levels in the estuarine sediments of Texas shows that Corpus Christi Bay has anomalously high concentrations of zinc and cadmium. Maps of elemental abundance within the bay indicate large concentration gradients, the highest values being near the harbor entrance. Seasonal determinations of metal levels in the harbor and bay waters also revealed variations with time. During summer, stagnation of the harbor water increases the concentration of metals so that significant quantities precipitate in the reducing environment of the bottom water. In winter, the exchange of water between the bay and the harbor increases, and metals are redissolved from harbor deposits, washed into the bay, and adsorbed by particles settling to the bottom. 0
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correspondence should be addressed.
During a survey of the trace-element distribution in the sediments of Texas bays and lagoons, anomalous zinc and cadmium levels were found in Corpus Christi Bay. Because zinc has been found to be detrimental to fish and other aquatic life (Pettyjohn, 1972) and because cadmium is a known toxin to man, these elements pose a threat to the estuarine system. Although zinc does not appear to be highly concentrated in the marine food chain (IDOE, 1972), it may pose a greater hazard in the dissolved state where it can interact freely with nectonic life. Cadmium, on the other hand, does become concentrated in the food chain and is therefore a hazard in any chemical state. This report presents data on the distribution of these elements in the sediments, their seasonal variations, and the pathways by which they move within the estuarine system. Volume 8,Number 3, March 1974
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