NOTES
Development of Sampling and Analytical Procedure for Determining Hexachlorobenzeneand Hexachloro-I,3-butadiene in Air Jon B. Mann,' Henry F. Enos, Jorge Gonzalez, and John F. Thompson Environmental Protection Agency, Pesticide and Toxic Substances Effects Laboratory, National Environmental Research Center, Research Triangle Park, N.C. 2771 1 Chromosorb 101 efficiently trapped vapors of hexachlorobenzene (HCB) and hexachloro-1,3-butadiene(HCBD) from air a t a sampling rate of 3 l./min. No loss of efficiency was noted with sampling times of u p to 3 hr. Increasing the sampling rate to 10 l./min. for 1 h r decreased the efficiency by 20%. The method as described has a detection limit of 28 ng of hexachlorobenzene per cubic meter of air.
Table I. Trapping Efficiency for HCB and HCBD on Chromosorb 101 No. of replicates
Air ng/m3
5 2 2 2
5560 1666 1110 1850 370
1hr, 1 hr, 1hr, 3 hr, 3 hr,
3
4170
1 h r , 2 Ipm
1
A recent episode in which the guidelines for hexachlorobenzene (HCB) in meat (0.3 ppm) was exceeded prompted a n investigation into the source of the contamination. The grass in pastures around certain chemical plants was found to contain hexachlorobenzene (HCB). Air pollution was considered as one possible source of this contaminant. An efficient, portable, air-sampling device, which would yield HCB in a form amenable to subsequent analysis by electron capture gas chromatography, was needed. T h e objective of this study was to develop, evaluate, and field test such a device. An on-going in-house research program designed to improve methodology for determining pesticides in air provided clues to the best approach for resolving this problem (Seiber et al., 1973). An ethylene glycol impinger system originally described by Miles et al. (1970) and later adapted by Enos et al. (1972) was less desirable for field use than a solid adsorbent trap attached t o a portable battery-powered air pump. The solid adsorbent suggested for this work (Seiber, 1973)was Chromosorb 101.
Sampling time and rate
HCB 3 Ipm 10 Iprn 3 Ipm 3 Ipm 3 Ipm
Trapping efficiency, % I
Range
92.9 79.0 97.0 91.6 99.5
88.5-97.5 78.0-80.0
100.5
98.0-103
87.4-95.7 98.9-100
HCBD
Experimental Preparation of Chromosorb 101. Chromosorb 101 (60/ 80 mesh) was extracted for 4 hr using a Soxhlet apparatus charged with 5% acetone in methanol. Six washing cycles per hour proved adequate. A similar wash with hexane was repeated twice. T h e Chromosorb 101 was dried for 30 min a t 70°C. A 1-gram portion was extracted with 20 ml of hexane by shaking in a 50-ml test tube for 20 min on a reciprocating mechanical shaker. A 4-ml aliquot of the supernatant was concentrated to 1 ml and a 5 p l . portion injected into a gas chromotograph for the purpose of establishing the background contribution from the adsorbent. Injection was made into a gas chromatograph containing a 1.5% OV-17/1.95% QF-1 column heated to 150°C and equipped with a n electron capture detector. T h e sensitivity of the gas chromatography system was such t h a t a 50-pg injection of HCB resulted in a t least a 50% fullscale deflection with a noise level of less than 2%. 1
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Environmental Science & Technology
Figure 1 . Field sample collected at rate of 2 I jmin for 1 h r was equal to 900 ng HCB/m3 air diluted to 40 ml
Figure 2. One gram Chromosorb 101 after cleanup, 20 mlconcentrated to5ml
P r e p a r a t i o n of Collection Tube. A 4-in. length of IO-mm i.d. glass tubing was fire polished a t both ends. A crimp was made about 1 in. from one end of the tube to retain a small plug of glass wool. One gram of Chromosorb 101 was placed in t h e tube followed by another plug of glass wool. Evaluation of Collection Tube. Known amounts of HCB and hexachlorobutadiene were placed in a U tube and the U tube was connected to the collection tube. After air was drawn through t h e tubes at a known rate for a specified period of time the Chromosorb 101 was transferred to a test tube containing 20 ml of hexane and shaken for 20 min. Analysis was completed by injecting a 5 - ~ 1 . aliquot into a gas chromatograph equipped and operated as described above. Results and Discussion T h e results in Table I indicate t h a t a high level of trapping efficiency can be obtained for vapors of HCB and HCBD. HCB was trapped efficiently at a sampling rate as high as 10 l./min (lpm). For most purposes, a rate of 2 l./min and a sampling interval of 3 hr should be sufficient. Under these conditions and with a preliminary concentration of the extract ( 4 to l), a limit of detection of 28 ng/m3 of air [about 22 parts per trillion ( p p t ) ] can easily be achieved. HCB was stable when adsorbed on Chromosorb 101 from the vapor phase and stored a t room temperature for u p to 6 days. This allowed sufficient time to transport samples from t h e field to the laboratory.
Field evaluation of the sampling device was accomplished by obtaining samples upwind and downwind of a chemical plant manufacturing perchloroethylene. Samples were also taken around a land fill area used by the plant for disposing of waste chemicals. An air sample taken downwind of the plant contained 990 ng HCB/m3 while a n upwind sample contained 915 ng/m3. An air sample taken on a dustless day in the vicinity of t h e land fill contained 18.6 mcg/m3. HCBD was also found in t h e samples described above b u t it was not quantitated. T h e identities of H C B and HCBD in the field samples were confirmed by mass spectrometry. Figure 1 is a chromatographic tracing depicting both the H C B and HCBD as they appear in a field sample. Figure 2 is typical of t h e background obtained from Chromosorb 101 when it was prepared and evaluated as described in this method. Literature Cited Enos, H. F., Thompson, J . F., Mann, J . B., Moseman, R. F.. “Determination of Pesticide Residues in Air.” 163rd ACS Kational Meeting, Boston, Mass., April 1972. Miles, J . W., Fetzer, L. E., Pearce, G. W., Enuiron. Sci. Tech., 4, 420-5 (1970). Seiber, J., Shafik, T., Enos, H. F., progress report, Primate and Pesticides Effects Laboratory, US.Environmental Protection Agency, Perrine, Fla., 1973. Seiber, J., Department of Environmental Toxicology, University of California, Davis, Calif., private communication, 1973. Receiued for reuieu: August 31, 1973. Accepted Januap 15, I974
Rare Earth Element Composition of Atmospheric Particulates Mark J. Potts,’ Charles W. Lee, and James R. Cadieux Center for the Biology of Natural Systems, Washington University, St. Louis, Mo. 63130
The relative and absolute rare earth element (REE) concentrations of atmospheric particulate matter are still very poorly known. T h e REE do not constitute a n apparent health hazard, although their toxicology is not well defined. However, as a tool for determining sources and particulate formation processes, they warrant further study. Analyses for nine of the REE (sufficient to define relative distribution patterns) are reported for three air particulate samples collected in t h e metropolitan St. Louis area. Differences are observed t h a t , with additional data, should prove useful in defining source materials and modes of atmospheric particulate loading.
Very few d a t a on the rare earth element ( R E E ) contents of air particulates are available in t h e literature. In addition, the available information is either of high uncertainty (Henry and Blosser, 1971) or incomplete (Gordon et al., 19i3; Kay et al., 1973). T h e R E E contents of air particulates do not present a n obvious toxicological hazard a t their ng/m3 level but do perhaps warrant closer study for Present address, Texas Instruments Inc., Geophoto Services, P.O. Box 5621, Dallas, l’ex. 75222. To whom correspondence should be addressed.
their ability as tracers and discriminators. The utility of the R E E in determining the origin and formation processes of natural materials such as rocks and minerals is well documented (Haskin and Frey, 1966; Herrmann, 1970). T h e processes by which the REE were added to the total particulate loading of the atmosphere are certainly different from geologic processes but may be amenable to the same type of analysis based on both absolute HEE contents and relative R E E fractionations. The R E E behave as an essentially coherent group of elements. Relative fractionations within the group or anomalous contents of individual elements (notably Ce and E u ) are generally the most useful types of information, and they reflect directly on the formation processes and sources. T o effectively view such differences it is necessary to normalize, element by element, t h e concentrations of t h e R E E in a sample by those in some standard reference material. Doing so not only removes the nuclear structure effect causing the abundances of even atomic number elements to exceed those of odd atomic number elements in nature (Oddo-Harkins rule) but also yields a n immediate comparison with the reference material. T h e R E E d a t a (Table I and Appendix) for three air filtrate samples from t h e metropolitan St. Louis area have been normalized to the average R E E contents of shales and are plotted versus atomic number in Figure 1. This Volume 8, Number 6, June 1974
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