Works Assoc., 66, 703 (1974). (3) Jolley, R. L., Enuiron. Lett., 7, 321 (1974). (4) Jolley, R. L., Jones, G., Pitt, W. W., Thompson, J. E., in “Water Chlorination: Environmental Impact and Health Effects”, Jolley, R. L., Ed., Ann Arbor Science, Ann Arbor, 1978, pp 105-38. (5) Helz, G. R., Hsu, R. Y., Limnol. Oceanogr., 23,858-69 (1978). (6) Rook, J . J., Gras, A. A . , van der Heijden, B. G., de Wee, J., J . Enuiron Sci. Health, Ser. A , 13,91 (1978). ( 7 ) Provasoli, L., in “The Sea”, Hill, M. N., Ed., Vol. 2, Wiley, New York, 1963, pp 163-234. (8) Prakash, A , , Rashid, M. A,, Limnol. Oceanogr., 13,598 (1968). (9) Sieburth, J. M., Jensen, A,, in “Organic Matter in Natural Waters”. Hood. D. W.. Ed.. Universitv of Alaska Institute of Marine Science, 1970, pp 203-24. (10) Ingle, R. M.. Martin, D. F.. Enciron Lett.. 1.69 (1971). (11) Milanovich, F. P., Wilson, D. W., Yeh, Y., Nature (London),253, 460 (1975). (12) Giesy, J. P., Leversce, G. J.,Williams, D. R., Water R e s , 11,1013 i,-1977) - . . ,. (13) Sunda, W., Guillard, R. L., J . Mar. Res., 34,511 (~1976). (14) Rook, J. J., Enuiron. Sci. Techno/., 11,478-83 (1977). (15) Kwak, J . C. T., Nelson, R. W. P., Gamble, D. S., Geochim. Cosmochim. Acta, 1 8 , 993-6 (1977). (16) Germani, M. S.. Gokmen, I., Sigleo, A. C., Kowalczyk, G. S., Olmez, I., Small, A., Anderson, D. L., Failey, M. P., Gulovali, M. C., Choquette, C. E., Lepel, E. A., Gordon, G. E., Zoller, W. H., Anal. Chem., 52,240 (1980). (17) Menzel, D. M7., Vaccaro, R. F., Limnol. Oceanogr., 9, 138 (1964). (18) Helz, G. R., Sugam, R., Hsu, R. Y., in “Water Chlorination: Environmental Impact and Health Effects”, Jolley, R. L., Hamilton, D. H., Gorchev, H., Eds., Ann Arbor Science, Ann Arbor, 1978, pp 209-22. (19) Ghassemi, M., Christman, R. F., Limnol. Oceanogr., 13, 583 (1968). (20) Benes, P., Gjessing, E. T., Steinnes, E., Water Res., 10, 711 (1976). (21) Gachter, R., Davis, J. S., Marks, A., Enciron. Sei. Technol., 12, 1416 (1978). (22) Richards, F. A , , in “Chemical Oceanography”, Vol. 1, Riley, J,
P., Skirrow, G., Eds., Academic Press, New York, 1965, pp 61146. (23) Black, A. P., Christman, R. F., J . A m . Water Works Assoc., 55, 897 (1963). (24) Schnitzer, M., Khan, S. U., “Humic Substances in the Environment”, Marcel Dekker, New York, 1972. (25) Stuermer, D. H., Peters, K. E., Kaplan, I. R., Geochim. Cosmochim. Acta, 42,989 (1978). (26) Glaze, W. H., Peyton, G. R., in “Water Chlorination: Environmental Impact and Health Effects”, Vol. 2, Jolley, R. L., Hamilton, D. H., Gorchev, H., Eds., Ann Arbor Science, 1978, pp 3-14. (27) Sugam, R., Ph.D. Thesis, University of Maryland, 1977. (28) Stanbro, W. D., Smith, W. D., Enuiron. Sci. Technol., 13,446 (1979). (29) Roberts, W. P., unpublished Ph.D. Thesis, George Washington University, 1971. (30) Jenne. E. A.. Girvin. D. C.. Ball. J. W.. Burehard. J. M.. in “Env’ironmental Impacts of Artificial ‘Ice Nucleating Agents;’, Klein, D. A., Ed., Dowder, Hutchison and Ross, Stroudsburg, Pa., 1978, pp 41-62. (31) Carpenter, J . H., Smith, C. A., in “Water Chlorination: Environmental Impact and Health Effects”, Jolley, R. L., Hamilton, D. H., Jr., Gorchev, H., Eds., Ann Arbor Science, Ann Arbor, 1978, pp 195-208. (32) Kopfler, F. C., Melton, R. G., Lingg, R. O., Coleman, W. E., in “Identification and Analysis of Organic Pollutants in Water”, Keith, L. H., Ed., Ann Arbor Science, Ann Arbor, 1976, pp 87104. (33) Nicholson, A. A,, Meresz, O., Lemyk, B., Anal. Chem., 49,814 (1977). (34) Pfaender, F. K., Jonas, R. B., Stevens, A. A., Moore, L., Haas, J . H., Enuiron. Sci. Technol., 12,438 (1978).
Receiued for reuiew September 4,1979. Accepted February 11,1980. This work u a s supported by the Maryland Power Plant Siting Program. This work was presented at the 177th National Meeting of the American Chemical Society, Honolulu, April 1979, Abstr. E N V R 92, and at the Third Conference on Water Chlorination, Colorado Springs, October 1979.
Field Comparison of Polyurethane Foam and Tenax-GC Resin for High-Volume Air Sampling of Chlorinated Hydrocarbons W. Neil Billings and Terry F. Bidleman” Department of Chemistry and Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, S.C. 29208
The comparative efficiency of porous polyurethane foam ( P P F ) and Tenax-GC resin for collecting polychlorinated biphenyls (PCB) and chlorinated pesticides from 300-1600 mJ of air was determined by side-by-side sampling with each adsorbent in the city of Columbia, S.C. Front and backup adsorbent traps were analyzed separately to determine the penetration of chlorinated hydrocarbon vapors. Low molecular weight PCB (Aroclor 1016) was effectively retained by both adsorbent systems a t air volumes of 300-700 m3. Hexachlorobenzene (HCB) was very poorly retained by P P F , but efficiently collected by Tenax. Throughout the air volume range both solid adsorbents had very good collection efficiency (>95S’c of the material found on the front adsorbent trap) for higher molecular weight PCB (Aroclor 1254),chlordane, DDT, and toxaphene. Average relative standard deviations for replicate collections with a given adsorbent ranged from 8 to 22%. Side-by-side measurements of CHC in Columbia air using PPF and Tenax agreed within 5-1570 except for HCB, for which higher values were determined by Tenax samvline. The ubiquity and persistence of many chlorinated hydrocarbons (CHC) have given rise to the need for developing 0013-936X/80/0914-0679$01.00/0
@ 1980 American Chemical Society
adequate collection methods for determining their atmospheric concentrations. Determination of low parts per trillion (10-9 g/m3) levels of polychlorinated biphenyls (PCB) and pesticides requires that hundreds of cubic meters of air be sampled to provide enough material for analysis. These high air volumes greatly exceed the capacities of bubblers and impingers; as a result solid adsorbents have gained rapid acceptance for organic vapor sampling. A review of sampling methodology for airborne pesticides and PCB has been published by Lewis ( I ) . The collection efficiency of any solid adsorbent bed depends on the volatility of the organic compound being sampled and the total volume of air pulled through the bed. Porous polyurethane foam (PPF) has been used extensively for sampling airborne pesticides and PCB. Many CHC pesticides and high molecular weight PCBs are effectively trapped by PPF (2-7), but the more volatile PCB isomers (5-7) and hexachlorobenzene (HCB) (3)are less well retained. Laboratory studies show that PCB isomers are eluted through a P P F column by high-volume airflow in order of decreasing volatility, and that the vapor penetration is linear with total air volume ( 7 ) .Tenax-GC resin (2,6-diphenyl-p-phenylene oxide) has been used by several investigators to trap volatile organics under lowVolume 14, Number 6, June 1980
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Figure 1. Packed column chromatograms (SE-30/SP-2401) of the PCBIDDE fraction ( 7 5 ) of a Columbia, S.C. air sample (upper) and a mixed Aroclor 1016-Aroclor 1254 standard (lower). The division between the Aroclors is indicated by the dotted line
volume sampling conditions (8-13). The elution of low molecular weight chloroalkanes through a Tenax bed is controlled by vapor pressure, with the logarithm of retention volume related to the reciprocal of the absolute temperature (13). This study was undertaken to compare two solid adsorbents, PPF and Tenax, for field sampling of PCB and CHC pesticides with the objectives of determining: (a) the comparative collection efficiency of P P F and Tenax for CHC having different volatilities, by sampling urban air for 24-48 h, and (b) the sampling reproducibility, by carrying out replicate collections with the same adsorbent system.
Experimental Adsorbent Preparation. Porous polyurethane foam (PPF, density = 0.022 g/cm3) was obtained from Olympic Products Corporation, Greensboro, N.C., and was cut into plugs 7.6 cm thick X 7.6 cm diameter using a hole saw (7, 14). The foam plugs were extracted with reagent grade acetone followed by pesticide quality petroleum ether and dried in vacuo (2).Petroleum ether extracts of precleaned plugs were cleaned up by alumina chromatography (2), shaken with 7% fuming sulfuric acid, and analyzed by electron-capture gas chromatography (EC-GC).Blank values for the 7.9-g plugs were 9.1 f 6.9 ng of Aroclor 1016 and 4.6 f 2.6 ng of Aroclor 1254 (14 replicates). Tenax-GC resin was purchased in 35/60 mesh size from Applied Science Laboratories, State College, Pa. The Tenax in 10-g portions was placed in precleaned cellulose extraction thimbles and Soxhlet extracted for 24 h with pesticide quality petroleum ether. The extracts were cleaned up and analyzed as above. As received, different lots of Tenax contained 70-225 ng/g of Aroclor 1016 and 20-46 ng/g of Aroclor 1254.The clean Tenax was dried for 3-5 h in vacuo a t 40-50 "C. Reextraction of the dry Tenax with petroleum ether gave average blanks only slightly higher than those of PPF plugs: 16 f 17 ng of Aroclor 1016 and 11 8.8 ng of Aroclor 1254 for 10-g portions of Tenax ( n = 10). Sample Collection. Air was pulled a t 0.35-0.5 m3/min through a 10-cm diameter or 20 X 25 cm glass fiber filter followed by two 7.6-cm diameter X 7.6-cm thick PPF plugs or two 10-g Tenax traps (54-cm2cross section) using a Rotron DR-313 brushless pump (Rotron Corporation, Woodstock, N.Y.). The filter holder-adsorbent cartridge units were con680
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Figure 2. Capillary chromatograms of the same sample and standard as in Figure 1, 30-m SP-2100 column, direct injection, 150-200 OC at 2 "C/min
nected to the pump via 5-m flexible hose. Details of their construction are given in Bidleman et al. (14). The pressure drop just below the collector was monitored with a Magnehelic gauge (Dwyer Instrument Company, Michigan City, Ind.). The pressure drop was related to the volume flow rate by using an orifice calibrator, which was in turn standardized by using a Roots positive displacement meter. All experiments were carried out on the roof of the Physical Sciences Center near downtown Columbia, S.C. (population 380 000) 30 m above street level. Temperatures and relative humidities ranged from 0 to 40 "C and from 30 to 100%over the course of the experiments. Analytical Methods. Solid adsorbents were Soxhlet extracted with petroleum ether, dried in vacuo, and reused for subsequent sampling. Second extractions showed no carryover of CHC between samplings. For a few of the samples the glass fiber filters were also analyzed. Filters were refluxed with dichloromethane, and the chlorinated solvent was removed before analysis by refluxing with hexane. Sample extracts were cleaned up by alumina chromatography (2) and separated into four fractions on a silicic acid column (15).Fractions from the column were shaken on a vortex mixer with 7% fuming sulfuric acid. PCB and most chlorinated pesticides are stable to this treatment (16, 17). The PCB/DDE fraction from the silicic acid column was further treated with alcoholic potassium hydroxide. The cleaned up fractions were analyzed by EC-GC on two and occasionally three of the following columns: 1.5% SP2250/1.95% SP-2401,4%SE-30/6% SP-2401, and 3% OV-225 (Supelco, Inc., Bellefonte, Pa.). All columns were glass, 0.4 cm i.d. X 180 cm long (Tracor 222) or 0.2 cm i.d. X 180 cm long (Varian 3700), and were operated a t 170-210 "C with 25-60 mL/min nitrogen flow. Most analyses were carried out by packed column EC-GC, although during the later part of this study several samples were also examined by capillary EC-GC using a 30-m SP-2100 AA-grade Supelco column mounted in a Varian 3700 instrument. The improved resolution on the capillary column (Figures 1-4) was especially helpful in confirming our identification of multicomponent CHC (PCB and toxaphene). In addition, confirmatory tests were carried out
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Figure 3. Packed column chromatograms (SE-30/SP-2401) of the toxaphene fraction ( 75) of a Columbia, S.C. air sample (upper) and a toxaphene standard, also fractionated on silicic acid (lower). Polychloroterpenes quantified as toxaphene are marked with asterisks. In addition to column cleanup and fractionation, this sample has been treated with a fuming nitric-concentrated sulfuric acid mixture. Toxaphene is stable to this treatment ( 74,but many aromatic hydrocarbons, including PCB and the DDT group, are destroyed
on representative samples collected over the 2-year period. The presence of p,p’-DDT and cis-chlordane was confirmed by dehydrochlorination with alcoholic KOH to p,p’-DDE and 3-chlorochlordene. Polychloroterpene peaks identified as toxaphene were unaffected by treatment with a fuming nitric-concentrated sulfuric acid mixture, a procedure which destroys many aromatics including the DDT group (18).The altered GC traces produced by dehydrochlorinating airsample polychloroterpenes were compared to those of dehydrochlorinated toxaphene standards (19,20). Quantification of chromatograms was based on peak height; for PCB and polychloroterpenes, the total peak height of Aroclor and toxaphene standards was compared to that of the matching sample peaks. Analytical standards were obtained from the U.S. Environmental Protection Agency Pesticide Repository, Research Triangle Park, N.C.
Results and Discussion The collection characteristics of PPF and Tenax are summarized in Table I, where quantities of PCB and chlorinated pesticides found on the backup traps are expressed as a per-
Figure 4. Capillary chromatograms of the same sample and standard as in Figure 3, 30-m SP-2100 column, direct injection, 150-210 OC at 2 OC/min. Sample peaks identified as polychloroterpenes are marked with asterisks. The middle portion of the chromatogram (25-35 min) also contains some peaks which match the retention times of toxaphene components, but which are proportionally higher. This might be due to the greater loss of more volatile toxaphene components from treated agriculturalareas (27), or to the presence of other unidentified electron capturing compounds which survive cleanup procedures
centage of the front trap values. HCB is very poorly retained by P P F in all air volume ranges, as can be seen by the nearly equal proportions of HCB found on the front and backup traps. Tenax is far more effective in retaining HCB, and the levels of HCB found in ambient air using Tenax are several times higher than the HCB concentrations determined with PPF collection (Table 11).Tenax also appeared to have a slight advantage over P P F for collecting low molecular weight PCB, the difference being most noticeable at the higher air volumes. Little PCB or chlordane was retained by the glass fiber filter in a 24-h or longer sampling period, although on some days appreciable fractions of p,p’-DDT were filter-retained. Average percentages of filter-retained CHC in Columbia were: Aroclor 1016,
