Environ. Sci. Technol. 1992, 26, 1048-1052
High-Volume Air Sampler for Particle and Gas Sampling. 1. Design and Gas Sampling Performance Kenneth M. Hart,+ Lorne M. Isabelle, and James F. Pankow” Department of Environmental Science and Engineering, Oregon Graduate Institute, 19600 N. W. Von Neumann Drive, Beaverton, Oregon 97006
rn A high-volume air sampler was developed to collect organic compounds in the gas and particulate phases a t flows up to 1.4 m3/min. Quartz fiber or Teflon membrane filters can be employed; use of a backup filter allows correction for the direct adsorption of gaseous analytes to the filter. Most of the filtered air passes through two 1.27 cm thick polyurethane foam sheets (PUFSs) in series; the remainder passes through two Tenax cartridges in series. The thin, filter-size (20 cm X 25 cm) PUFSs permit high-flow rates with minimal pressure drop. An adequate sample volume can be obtained in a minimum amount of time, minimizing the probability that atmospheric concentration fluctuations will cause volatilization losses from, or adsorption gains to particles on the filter. With sample volumes of 500-700 m3, at 16 OC, breakthrough from the first PUFS was
Overall mean, blank-corrected concentrations computed after pooling individual event data for sums of front and back PUFSs with data for sums of front and back Tenax cartridges. *Ratios computed for data obtained with the sampler using two quartz fiber filters (QFFs) and with the sampler using a Teflon membrane filter (TMF) followed by a QFF. CNumberof events, 5. Ratios given are fl standard deviation (fls), where s has been calculated based on event-to-event variability. d < , =, or > than 1,95% confidence level.
Table 111. Mean Breakthrough B (%) Values ( f l s ) for Two 20 X 25 X 1.27 cm Polyurethane Foam Sheets (-0.022 g/cm3) for 12 Sampling Events" compound
B f Is
n-Alkanes 47 f 11 c 1 7 39 f 12 CIS 26 f 14 c19 16 f 12 c20 11 f 15 CZl 4f8 c16
compound PAHs acenaphthene fluorene phenanthrene anthracene fluoranthene pyrene
B f 1s 32 f 8 29 f 13 10 f 8 4f8 3f6 l f 2
"Since two samplers were used per event, the number of data values available for most compounds was 24. Average sample volume ( f l s ) , 594 f 97 m3, Average temperature (fls), 16.4 f 6.4 "C.
When E values are low (e.g., less than 20%), P + S will be a good estimate of the total influent concentration. For B values approaching 50%, there will be nearly total breakthrough, and P S will not be a good estimate of the total influent concentration. Table I11 provides mean B values for the PUFSs for 12 sampling events. There were no significant differences in the B values obtained using the samplers equipped with QFF front filters and those equipped with TMF front filters. There were also no obvious trends in the B values either over the sample volume range used or over the ambient temperature range encountered. (Average sample volume f l s = 594 f 97 m3; average temperature *ls = 16.4 f 6.4 "C.) Thus, the data in Table I11 represent pooled data for 24 samplings with the PUFSs. Essentially quantitative trapping on the two-PUFS configuration was achieved for the n-alkanes less volatile than Cls. That is, if a third PUFS had been used, of the total mass on the second plus third PUFS, 26% or less would have been on the third PUFS. The amount on the third PUFS (i.e., 7')would then correspond to 8% or less of the total amount found on the three-PUFS system, i.e., less than 8% of (P + S 7'). [Note that, for this example,
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9 X 100%/(26 9) = 2670, PS:T = 74:26:9, and 9 X 100%/(74 26 + 9) = 8%.] For the target PAHs, compounds less volatile than phenanthrene were trapped essentially quantitatively. Although the PUF configuration used in this study is different from the cylindrical plug approach used in other studies (e.g., refs 2 and 7), reasonable agreement was obtained for B at similar temperatures and ratios of volume sampled to mass of front PUF used. For example, for Cls, Ligocki and Pankow (7) obtained B = 12% at a sample volume/(PUF mass) ratio of 200 m3/3.4 g = 59 m3/g and 9 "C, while this study obtained an average B of 26% at a volume/(PUFS mass) ratio of -600 m3/14 g = 43 m3/g and the somewhat warmer mean temperature of 16.4 "C. It is important to note that the sampler could have been modified for use with thicker PUFSs. If that had been done, lower B values would have been obtained here. Usage of thicker PUFSs might be needed when sampling at ambient temperatures higher than those encountered here, or when sampling larger gas volumes for very low level constituents. However, it should be remembered that the Tenax cartridges will always provide a second analysis mechanism for compounds that are not adequately retained by PUF. Adsorbent sampling efficiency as a function of the number of theoretical plates N of the sorbent system and the retention volume has been studied (16,17). Bidleman et al. (18,19) have examined PUF under typical sampling conditions and determined N to be 1 plate per centimeter of foam for PAHs and organochlorines. Thus, the two-sheet system designed here has -2.5 theoretical plates for the compounds of interest. Chromatographic retention volumes on PUF have been reviewed by Pankow (20). Our results here are generally consistent with these other studies. Breakthrough of Target Compounds on Tenax-TA. For the five sampling events when Tenax cartridges were connected in parallel with the PUFSs, virtually no breakthrough from the primary cartridge was measured for any of the target compounds that could be quantitated. The low breakthrough was a result of the low sample volumes (-200 L), the quantity of Tenax used, the inherent high affinities of the target compounds for Tenax, and the relatively low sampling temperatures (mean temperature for the five events was -10 "C). Pankow (21) has reviewed the retention volume information available for Tenax. Comparison of Concentrations Obtained with PUFSs and Tenax ADCs. For the compounds which could be determined using both PUFS and Tenax cartridges, good-to-excellentagreement was obtained between the measurements. This is evidenced by PUFS/Tenax concentration ratiois in Table I1 that are close to 1.000, Ratios in the table that are less than, equal to, and greater than 1.000 at the 95% confidence level are denoted with , respectively. Generally, the compounds which demonstrated B values greater than 30% in Table I11 gave PUFS/Tenax ratios that are less than 1.000 at the 95% confidence level. Thus, under the conditions used here, compounds with volatilities equal to or less than that of C18and phenanthrene may be determined reliably with the PUFSs; if the concentrations permit, they may also be determined using the lower sample volume Tenax train. Under the conditions used here, alkanes such as C17and PAHs such as fluorene should not be determined with the PUFSs; the Tenax train will capture them more quantitatively. I t is not known why pyrene gave a ratio larger than 1.OOO on the TMF-QFF sampler. However, given the
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fact that this concentration ratio was still within 10% of 1.000, either the PUFSs or Tenax will probably be a reliable sorbent.
Conclusions This work indicates that existing high-volume air samplers can be modified with PUF sheets and Tenax cartridges to sample semivolatile organic compounds in the gas phase in ambient air. The use of PUF sheets rather than PUF plugs reduces pressure drop through the system. This allows large-volume samples to be obtained over relatively short periods, minimizing the probability that atmospheric concentration fluctuations will cause volatilization losses from or adsorption gains to particles on the filter. The design is a simple modification of an existing, filter-only high-volume sampler. Registry No. C16,544-76-3; C17,629-78-7; C18,593-45-3; CI9, 629-92-5; C20, 112-95-8; C21,629-94-7;C22,629-97-0;C23,638-67-5; C,, 646-31-1; CZ5,629-99-2; quartz, 14808-60-7;Teflon, 9002-84-0; Tenax, 24938-68-9; acenaphthene, 83-32-9; fluorene, 86-73-7; phenanthrene, 85-01-8; anthracene, 120-12-7;fluoranthene, 20644-0; pyrene, 129-00-0; benz[a]anthracene, 56-55-3; chyrsene, 218-01-9.
Literature Cited Eisenreich, S. J.; Looney, B. B.; Thornton, J. D. Environ. Sci. Technol. 1981, 15, 30-38. Bidleman, T. F.; Olney, C. E. Bull. Environ. Contam. Toxicol. 1974, 11, 442-447. Billings, W. N.; Bidleman, T. F. Environ. Sci. Technol. 1980, 14, 679-683. Cautreels, W.; Van Cauwenberghe, K. Atmos. Environ. 1978, 12, 1133-1141.
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Koenig, J.; Funcke, W.; Balfanz, E.; Grosch, B.; Pott, F. Atmos. Environ. 1980, 14, 609-613. Lewis, R. G.; Brown, A. R.; Jackson, M. D. Anal. Chem. 1977,49, 1668-1672. Ligocki, M. P.; Pankow, J. F. Anal. Chem. 1985, 57, 1138-1 144. Thrane, K. E.; Mikalson, A. Atmos. Environ. 1981, 15, 909-918. Yamasaki, H.; Kuwata, K.; Miyamoto, H. Environ. Sci. Technol. 1982, 16, 189-194. Pankow, J. F. Atmos. Environ. 1991,25A, 2229-2239. Hart, K. M.; Pankow, J. F. J . Aerosol Sci. 1990, 21 ( I S ) , 377-380. Benner, B. A,; Gordon, G. E.; Wise, S. A. Environ. Sei. Technol. 1989,23, 1269-1278. Hart, K. M. Ph.D. Dissertation, Oregon Graduate Institute, Beaverton, OR, 1989. Pankow, J. F.; Isabelle, L. M. Anal. Chem. 1984, 56, 2997-2999. Pankow, J. F.; Ligocki, M. P.; Rosen, M. E.; Isabelle, L. M.; Hart, K. M. Anal. Chem. 1988, 60, 40-47. Senum, G. I. Environ. Sci. Technol. 1981,15, 1073-1075. Lovkist, P.; Jonsson, J. A. Anal. Chem. 1987,59,818-821. Bidleman, T. F.; Simon, C. G.; Burdick, N. F.; Feng, Y. J. Chromatogr. 1984, 301, 448-453. You, F.; Bidleman, T. F. Environ. Sci. Technol. 1984, 18, 330-333. Pankow, J. F. Atmos. Environ. 1989,23, 1107-1111. Pankow, J. F. Anal. Chem. 1988,60, 950-958.
Received for review October 7,1991. Revised manuscript received January 6, 1992. Accepted January 21, 1992. The authors gratefully acknowledge that this work was supported in part by Grant R-816353-01-0 from the US. EPA.
