Envlron. Sei. Technol. 1982, 16, 121-124
the untreated natural sample, the kaolin flocs appear weaker. This would be expected because of the composition of the natural sample, which would produce a stronger floc than kaolinite alone. A pipet having a tip opening less than 2000 pm in diameter can, therefore, produce significant floc breakage; in the case of weak flocs, tip openings larger than 3000 pm in diameter are recommended. It should also be pointed out that, because the maximum floc size studied was only 65 pm in diameter, care in handling should be applied when dealing with larger flocs.
Conclusions The diameter of the pipet tip opening used for sampling suspended material for flocculation studies directly affects floc breakage. Extremely small pipet tip openings disrupt flocs of all sizes. Therefore, pipet tip openings should be larger than 2000 pm in order to minimize floc breakage. If flocs are large and/or weak, the tip opening of pipets should be larger than 3000 pm. All commercially available pipets have unacceptably small tip openings. Studies of flocs should include measurement to show that sampling methods do not disrupt flocs.
Literature Cited Berthois, L. Rev. Geogr. Phys. Geol. Dyn. VI 1961,1,39. Biddle, P.; Miles, J. H. Sediment. Geol. 1972, 7, 23. Edzwald, J. K. “Coagulation in Estuaries”; University of North Carolina Sea Grant Program Publication UNC-SG72-06; Chapel Hill, NC, 1972. Edzwald, J. K.; O’Melia, C. R. Clays Clay Miner. 1975,23, 39. Gibbs, R. J. J. Sediment. Petrol. 1977, 47, 237. Kranck, K. Sedimentology 1975,22, 111. Krone, R. B. “Flume Studies of the Transport of Sediment in Estuarial Shoaling Process”, Final Report to San Francisco District, U.S.Army Corps of Engineers, 1962. Schubel, J. R.; Kana, T. W. Powder Technol. 1972,6,9. Sheldon, R. W. Limnol. Oceanogr. 1968,13, 72. Zabawa, D. Science 1978,202,49. Gibbs, R. J. J. Sediment. Petrol. 1981, 51, 670. Gibbs, R. J. In “Suspended Solids in Water”; Gibbs, R. J., Ed.; Plenum Press: New York, 1974; p 3. Carder, K. L. Opt. Eng. 1979, 18, 524.
Received f o r review February 5, 1981. Revised manuscript received J u l y 28, 1981. Accepted October 12, 1981. Support of the Office of Naval Research under contract NOOO14- 75-C-0355 is appreciated.
Improved Method for Polychlorinated Blphenyl Determination in Complex Matrices Gall 6. Copland and C. Steven Gohmann” EMS Laboratories, Inc., 790 1 West Morris Street, Indianapolis, Indiana 4623 1
An improved method is described for pretreatment of samples for the determination of trace-level polychlorinated biphenyls (PCB’s) using conventional gas chromatography. After initial treatment with concentrated sulfuric acid, the samples were subjected to further digestion with potassium permanganate and ultrasound. Removal of digestion products was accomplished with a Florisil microcolumn, and analysis performed by packedcolumn gas chromatography. Various difficult matrices were subjected to the new procedure. High recoveries of PCB’s were obtained with minimal interferences. The method is fast, inexpensive and effective in many cases, particularly for road oils and sludges, where other methods are inadequate. It also provides detection limits well below acceptable tolerances set by current regulations.
Introduction Polychlorinated biphenyls (PCBs) were originally used as heat-transfer fluids, dielectric fluids for capacitors and transformers, and as hydraulic fluids for diecasting because of their thermal stability and nonflammable properties. They were found to be hazardous to human health, and a massive effort is underway to purge them from the environment. The analyst’s job, assisting in locating and quantifying contamination, becomes frustrating and inconclusive as the complexity of the matrix increases. Analysis in water is a fairly straightforward procedure (1, 2): the sample is extracted with a suitable solvent, concentrated to a known volumn, and analyzed by electroncapture gas chromatography. Oils and sludges, however, are unsuitable for solvent extraction, frequently contain large amounts of chlorinated hydrocarbons, industrial byproducts, and particulate matter, and at the same time have the highest potential for large concentrations of PCB’s. 0013-936X/82/0916-0121$01.25/0
Table I. Some Analytical Methods for the Determination of PCB’s in Complex Matrices (1)EPA electrolytic coliductivity ( 2 ) acid, then florisil, alumina, or silica gel (EPA electron-capture procedure) ( 3 ) florisil addition (4) SbCl, perchlorination (5) oil/methanol partition ( 6 ) column chromatography ( 7 ) permanganate digestion
Table I lists several approaches which have been used to separate complex waste materials from PCB’s. The Environmental Protection Agency has tentative guidelines which it is evaluating for testing various types of oils (3). The first of these methods is a simple dilution followed by analysis on an electrolytic conductivity detector. Halogenated compounds can interfere in this analysis. The second is a method which has been used with considerable success on biological materials, cleaner oils, and nonchlorinated solvents. This procedure (referred to hereinafter as the EPA electron-capture (EC) procedure) involves weighing an amount of sample, diluting with hexane, shaking with concentrated sulfuric acid, and removing impurities with a small Florisil, silica gel, or alumina column. This new method has been applied particularly to those cases in which the EPA electron-capture procedure was ineffective. The other methods currently in use for PCB determination require only a brief mention. Florisil addition involves diluting the sample and shaking with Florisil to adsorb impurities. Perchlorination with antimony pentachloride involves converting all of the PCB present to a single compound, decachlorobiphenyl (4). Although effective, the procedure is time-consuming and requires the analyst to use a highly toxic reagent. Oil/methanol
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Table 11. Precision and Accuracy Data Based on Quadruplicate Analyses of Virgin Lubricating Oil Spiked with Three Different Aroclor Mixtures PRECISION & ACCURACY AT 1-10 Uglg AVO. %
DEV'AT'oN
1\
I I
PCB 1242 PCB 1254 PCB 1260 97%
1
\123%
1\
95%
1
\
66%
KMn04 METHOD
I%
-
0
10
5
15
20
MINUTES
Flgure 1. Progressive analysis of a chlorinated alkane mixture in a cutting oil: (A) Aroclor 1254 standard: (B)sample subjected to EPA electron-capture procedure: (C) sample subjected to new procedure; (D) sample subjected to new procedure after being splked wlth Aroclor 1254.
partition consists of extracting the oil with a known amount of methanol to extract a consistent 30% of the PCB concentration. Unfortunately, much of the oil dissolves in the methanol, too, making it unusuable for determinations at low levels. Column charomatography is time-consuming and uses large amounts of expensive solvent (5,6). The goal in the development of an analytical procedure is a method that is fast, accurate, and inexpensive and selectively eliminates interferences without significantly altering the measurable PCB concentration. The new permanganate digestion method approximates these conditions rather well, particularly in cases which were not amenable to analysis in the past. Experimental Section The instrumentation used in the study consisted of a Hewlett-Packard 5730A gas chromatograph equipped with a Nickel-63 electron-capture detector, an H / P 3380A integrator, and an H / P 7672A autosampler. The following chromatographic conditions were used: 1.5% OV-17/ 122
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1%
1%
1.95% QF-1 on Supelcoport packed in a 6-ft long, 2-mm i.d. glass column with argon/methane carrier gas at 60 mL/min, 200 "C isothermal oven temperature, at attenuation 64. Other equipment and supplies required included concentrated sulfuric acid, 5% aqueous potassium permanganate, 2-dram glass vials with Teflon-lined screw caps, Pasteur pipets, activated Florisil (activated at 130 OC for at least 24 h), glass wool, anhydrous sodium sulfate, and an ultrasonic bath. Using the EPA procedure as a framewok, we added two small but significant steps. Relying on the ability of polychlorinated biphenyls to withstand chemical oxidation, we subjected the samples to various strong oxidizing agents after initial treatment with concentrated acid in an attempt to digest the remaining impurities. The acid was removed from the vial with a pipet before addition of the oxidizing agent. A 5% aqueous solution of potassium permanganate was chosen as the most promising. The most effective method of mixing the sample proved to be an ultrasonic bath. Shaking the mixture vigorously, even for several minutes, was not as effective. Fifteen minutes in the sonic bath appears to be the optimum time for destruction of impurities with highest recovery of PCB's. The following is the complete permanganate digestion procedure: (1) Weigh 50-100-mg sample into a 2-dram vial. (2) Dilute to 2 mL with hexane. (3) Add 2 mL of concentrated sulfuric acid. (4) Cap tightly with a Teflon-lined cap and shake vigourously for 30 s. Allow layers to separate. (5) With a Pasteur pipet, draw out the acid layer. (The small amount of acid remaining in the vial will not disturb the analysis.) (6) Add 2-3 mL of 5% aqueous potassium permanganate solution. Cap tightly. (7) Suspend the vial in a sonic bath for 15 min, making sure the water level in the bath is above the liquid level in the vial. (8) Allow the layers to settle. (Centrifugation may be necessary if large amounts of particulate oxidation products are present.) (9) Pass the solvent layer through a Florisil microcolumn (made by packing a Pasteur pipet with 6-8 cm of Florisil and 0.5 cm of anhydrous sodium sulfate); wash the permanganate layer thoroughly with
1
'I
0
5
10 MINUTES
15
Flgure 2. Progressive analysis of a waste crankcase oil: (A) Aroclor 1260 standard; (B) sample subjected :o EPA electron-capture procedure; (C) sample subjected to new procedure; (D) sample subjected to new procedure after being spiked with Aroclor 1260.
fresh hexane 2-3 times and add the washings to the top of the column. (10) Elute with 3-4 mL of hexane. (11) Concentrate to a desired volume, if necessary. (12) Analyze by electron-capture gas chromatography. Three particularly troublesome samples were each analyzed by the EPA procedure, the permanganate digestion procedure, and the permanganate digestion procedure spiked with various PCB mixtures before the analysis. In addition, several samples of a clean oil were spiked with various PCB mixtures and analyzed via the new method to determine precision and percent recovery. Finally, standard solutions of three PCB mixtures were subjected to permanganate and ultrasound without acid or Florisil treatment to determine the loss attributable to the modifications in the method.
Results and Discussion Figures 1-3 show the progressive improvement in three practical samples. These samples were chosen out of a group actually received at an analytical laboratory because of their particularly troublesome characteristics. In Figure 1A is a standard Aroclor 1254 mixture, 0.54 ppm by mass. Figure 1B is a chlorinated alkane mixture
0
5
10 MINUTES
15
Figure 3. Progressive analysis of a refinery oil sludge emulsion: (A) Aroclor 1242 standard; (B) sample subjected to EPA electron-capture procedure; (C) sample subjected to new procedure; (D) sample subjected to new procedure after being spiked with Aroclor 1242.
in a cutting oil subjected to the EPA electron-capture procedure. The contamination is too severe for any quantitation. Figure 2C is a second similar quantity of the same subjected to the permanganate digestion. The contamination has been noticeably reduced. Finally, Figure 1D is the sample spiked with 1.52 pg of Aroclor 1254 and digested under the conditions of the new method. The recovery of this spike was 96%,somewhat high compared to average recovery from clean oils, indicating that trace contaminants may remain. The sample chromatogram is, however, vastly improved. Figure 2 shows a similar progression in a used crankcase oil. This particular sample contains a fairly high concentration of Aroclor 1260, but it is only after the permanganate digestion (Figure 3C) that the Aroclor 1248 concentration can be recognized and quantified as well. Figure 2D is the same sample spiked with 0.56 pg of Aroclor 1260. There was a 61% recovery of this spike, close Environ. Sci. Technol., Vol. 16, No. 2, 1982
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Environ. Sci. Technol. 1982, 16, 124-126
to the average percent recovery expected. Figure 3 shows again the same progressive improvement in an emulsified oil sludge sample. This cannot be regarded as a completely satisfactory analysis, but it is possible to establish a detection limit below 50 ppm after the permanganate digestion, allowing at least some information to be gathered. Finally, Table I1 shows some precision and percent recovery data obtained by spiking clean lubricating oil with three different Aroclor mixtures. The EPA electron-capture procedure is precise and accurate but, as has been seen, inadequate in some cases. The permanganate digestion method destroys a certain amount of the PCB’s, but with reasonable precision. The control data indicates that most of the PCB loss is indeed occurring in the permanganate/ultrasound step of the procedure, at least for Aroclors 1242 and 1260. As the data indicate, the problems involved in determining PCB’s in oil cannot be considered solved, but the permanganate digestion method improves the situation
considerably. Further work should be done to determine the relationship between time in the sonic bath and degradation of PCB concentration. (Although no explosions or other violent reactions have been observed in applying this technique to several hundred samples, care should be exercised whenever acid, permanganate, and organic materials are mixed.)
Literature Cited (1) USEPA. “Methods for Polychlorinated Biphenyls (PCBs) in Industrial Effluents”, 1973. ( 2 ) “Federal Register”; Dec 3, 1979; Vol. 44, No. 233,69501. (3) USEPA Request for Proposals No. CI 80-0500, “Validation of Procedures for the Determination of PCB’s in Oil”. (4) Stahr, H. M., Ed. “AnalyticalToxicology Methods Manual“; Iowa State University Press: Ames, IA, 1977; p 310. (5) Ogata, J. N., e t al. J. Chromatogr. 1980, 189, 425-7. (6) USEPA. “Methods Development for Determination of Polychlorinated Hydrocarbons in Municipal Sludge,” 1980.
Received for review April 30,1981. Accepted October 22, 1981.
Atrnospherlc Trace Gases over Chlna R. A. Rasmussen and M. A.
K. Khalll”
Department of Environmental Science, Oregon Graduate Center, 19600 N.W. Walker Road, Beaverton, Oregon 97006 J. S. Chang
Lawrence Livermore Laboratory, University of California, P.O. Box 808, Livermore, California 94550
rn Flask sampling, EC/GC, and FID/GC techniques were used to measure the concentrations of CO, CH,, CH3C1, N20, CCl,, CH3CC13,CC13F, CC12F2,and CHClF2 in the air over four urban and three rural areas in the People’s Republic of China. The results were compared with the concentrations of these trace gases found over urban and rural areas of Oregon, U.S.A. More CCl, and CH3Clwere found over Chinese cities than over Oregon cities or over rural China. CO, CH3C1, N20, and CHI were all significantly more abundant over rural China than over the clean background site in Oregon. In China rural sources of CO and CH3C1 include smoldering combustion in homes, whereas rice paddies and biogas conversion may be sources of CHI. Our results show that China may have significant anthropogenic sources of CHI, N20,and CC4,all of which are increasing in the atmosphere and may alter the earth’s climate if their increases continue for a long time.
Introduction For a long time, people living in cities have been aware of hazardous air pollution in the form of smoke and haze, but over the past decade new fears have emerged, that the unseen gaseous emissions from industrialized cities may eventually alter the earth’s total atmospheric environment. Concerns have centered around the environmental consequencies of depleting the stratospheric ozone layer, altering the temperature of the lower atmosphere and affecting the earth’s climate (1,2). To address these complex issues requires more detailed observations of the atmospheric distributions of trace gases than are currently available (3). In particular, the natural trace gases, CHI, C02, CO, CH3C1,and N20, likely to be increased by human activities, and the purely anthropogenicgases CC13F (F-ll), CC1,F2 (F-12), CHClF2 (F-22), CC14, and CH3CC13 are among those believed to be important in determining the 124
Envlron. Scl. Technol., Vol. 16, No. 2, 1982
effects of human activities on the global environment (4). Recently it has been established that methane (CH,) and nitrous oxide (N20) are increasing in the earth’s atmosphere (5-9). The magnitudes and the locations of the anthropogenic sources of these trace gases can be determined probably by no other means than atmospheric measurements. As a part of this goal we report our first measurements of CHI, CO, CH,Cl, N201.CC14,CH3CC13, F-11, F-12, and F-22 in the urban (Beijing, Hangzhou, Nanjing, and Wuxi) and rural (Xi’an, Luoyang, and Suzhou) areas of the People’s Republic of China-a country containing a fourth of the world‘s human population. We also measured these trace gases over Oregon, U.S.A., cities (Portland, Oregon City, Newberg, Salem, Corvallis, and Beaverton) and over the background site at Cape Meares, OR. Exact locations of the cities are given in the microfilm appendix (see paragraph at the end of the text regarding supplementary material). We recognize that our data are few and we do not have supporting meterological data; still the results of the experiment suggest that in China there may be significant anthropogenic sources of CHI, CH3C1, CO, N20, CCl,, and even CH3CC13.
Measurements and Analyses The samples of air were collected in stainless-steel canisters and brought to the Atmospheric Trace Gas Laboratory of the Oregon Graduate Center (OGC), where the halocarbons and N20 were measured by electron capturegas chromatography (EC/GC) techniques and CO, COz, and CHI by FID-M/GC methods (IO, 11). The collection techniques, preparation of the canisters with inert internal surfaces, and the methods of analysis have all been designed and experimentally established to provide accurate and precise atmospheric measurements of the nine trace gases which we consider in this study. The
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0 1982 American Chemical Society
