Anal. Chem. 1992, 64, 2858-2801
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Laboratory Evaluation of Polyurethane Foam-Granular Adsorbent Sandwich Cartridges for Collecting Chlorophenols from Air Gregory W. PattonJ94 Laura L. McConnellJ~~ Mark T. Zaranski,t*lland T e r r y F. Bidleman'*tJ.f Department of Chemistry, Marine Science Program, and Belle W.Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, South Carolina 29208
Adsorbent traps contalnlng 5-6 g of Tenax-GC sandwlched betweentwo 3tm-thlck polyurethane foam (PUF) plugs were used to collect SIX dl- to tetrachlorophenols from 285-380 m3 of analyt-ked ak. Laboratory experknentswere conducted by vaporlzlng known quantltles of chlorophenols Into a clean airstream for sampling by a General Metal Works PS-1 hlghvolume alr sampler at 20 OC. Chlorophenol8 were Soxhlet extracted from the adsorbent traps, derlvatlzed wlth acetlc anhydrlde, and anatyzedby gas chromatography uslng electron capture detectlon. Collectioneffkkncies,determined by mass balance of the quantltles Introduced and recovered, averaged 63-96% for lndlvldual compounds, wlth an overall mean of 83%. The PUF-Tenax traps should be sultable for amblent alr sampllng at alr volumes up to at least 380 ms wlth alr temperatures 520 OC.
INTRODUCTION Chlorophenols are a group of semivolatile organic compounds that are used as pesticides, bactericides, wood preservatives, and synthetic intermediates. They are also byproducts of the chlorine bleaching process used in pulp and paper mills. Most chlorophenols are on the U.S. Environmental Protection Agency priority pollutant list, and reliable air collection methods are needed for these compounds. Recently, chlorophenols have been investigated as indicator parameters for polychlorinated dibenzodioxins and furans from municipal waste combustion.' Little information on chlorophenols in ambient air is available, but measurements in Portland, OR,2 Windsor, Ontario,3 and Hamburg, Germany? showed low ng/m3 concentrations. Vapor pressures of di- through tetrachlorophenols range from about 13 to 0.4 Pa at 20 "C (see Table I) and are similar to those of chlorobenzenes and two-ring aromatic hydrocarbons. Semivolatile organic compounds in this volatility range are poorly collected by high-volume air samplers using Department of Chemistry, University of South Carolina. Present address: Battelle, Pacific Northwest Laboratories, P.O. Box 999, Richland, WA 99352. Present address: Agricultural Research Service, US.Department of Agriculture, Beltsville, MD 20705. 11 Present address: TMS, Division of Coast-to-Coast Analytical Services, 7726 Moller Rd., Indianapolis, IN 46268. 1 Marine Science Program, University of South Carolina. Present address: Atmospheric Environment Service, 4905 Dufferin St., Downsview, Ontario M3H 5T4, Canada. (1) ()berg, T.; Bergstrbm, J. Chemosphere 1989, 19, 337. P.; Pankow, J.F.Enuiron. Sci. Technol. (2) Leuenberger,C.;Ligocki,M. 1985,19, 1053-1058. (3) Dann, T. Detroit Incinerator Monitoring Program Data Report #4, PMD-90-8;River Road EnvironmentalTechnology Center, Environment Canada Conservation and Protection: Ottawa, 1990; Appendix B-G. (4) Bmckmann, P.; Kersten, W.; Funcke, W.; Balfanz, E.; Kbnig, J.; Theisen, J.; Ball, M.; Pipke, 0. Chemosphere 1987,17, 2363-2380. (5) Weast, R. C.; Astle, M. J.; Beyer, W. H. Handbook of Chemistry and Physics, 65th ed.; CRC Press: Boca Rotan, FL, 1984; p D-204. +
t
Table I. Chlorophenol Quantities Used in Collection ExDeriments compd 2,6-DCP 2,4-DCP 3,4-DCP 2,4,5-TCP 2,4,6-TCP 2,3,4,5-TeCP
Pg
0.35-4.8 0.37-4.8 0.30-5.8 0.24-23 0.17-3.2 0.077-1.7
*
Reference 5. Value not available.
Pa.
PLO,
(Pa) (20 "CP 8.2 13.1 b 4.1 2.6 b, c
LO for 2,3,4,6-TeCP = 0.44
polyurethane foam (PUF) alone as an adsorbent. Collection of these semivolatile compounds is greatly improved by using granular adsorbents with higher specific surface areas such as Tenax-GC or XAD-2, either alone- or sandwiched between two PUF slices.gJ0 We have demonstrated that a high-volume air sampler equipped with PUF-granular adsorbent sandwich cartridges can be used to collect two-ring aromatic hydrocarbons, chlorobenzenes, and hexachlorocyclohexanes (HCHs)." The objective of this study was to evaluate PUFTenax-GC as a solid-phase adsorbent for high-volume air sampling of chlorophenols. EXPERIMENTAL SECTION Sampling Train and Test Procedures. A description of the apparatus used for collection efficiency studies is given in Zaranski et al.I1 Briefly, a General Metal Works, Inc. PS-1highvolume sampler was modified by attaching a stainless steel mixing chamber to the top of the filter head assembly. Air entering the mixing chamber was cleaned by passage through a glass-fiber filter followed by an activated charcoal bed. A mixture of chlorophenols (0.077-23 pg each) in 25-50 p L of methanol or hexane was injected into a heated glass port, vaporized,and swept into the clean airstream. The outlet of the mixing chamber led into the PS-1sampler containing two PUF-granular adsorbent traps, each with 5.8-cm i.d. The sandwich traps were filled with 5-6 g of Tenax-GC (35/60 mesh, Alltech Associates) between two 3-cm-thickPUF slices (density = 0.022 g/cm3,Product No. 3014, Olympic Products Corp., Greensboro, NC). Intact traps were precleaned before use by Soxhlet extractionwith 15 % ethyl ether in petroleum ether (15% EE/PE) and then dried and stored as previously described." After injection of test compounds, air was pulled through the mixing chamber at 0 . 1 4 3 m3/min to sweep the chlorophenols from the mixing chamber into the adsorbent bed. The pressure
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0003-2700/92/0364-2858$03.00/0
(6) Billings, W. N.; Bidleman, T. F. Enuiron. Sci. Technol. 1980, 14, 679-683. (7) Billings, W. N.; Bidleman, T. F. Atmos. Enuiron. 1983, 17, 383391. (8) Arey, J.; Atkinson, R.; Zielinska, B.; McElroy, P. A. Enuiron. Sci. Technol. 1989,23, 321-327. (9) Lewis, R. G.; Jackson, M. D. A d . Chem. 1982,54,592-595. (10) Zaranski, M. T.; Bidleman, T. F. J. Chromatogr. 1987,409,235242. (11) Zaranski, M. T.; Patton, G. W.; McConnell, L. L.; Bidleman, T. F.; Mulik, J. D. Anal. Chem. 1991, 63, 1228-1232.
0 1992 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 64, NO. 22, NOVEMBER 15, 1992
drop behind the adsorbent cartridges was measured with the Magnehelic gauge on the PS-1 sampler and related to flow rate using the PS-1orifice calibrator. Experiments were carried out in a controlled-temperature room at 20 f 2 OC. In some experiments, chlorophenols were vaporized from a spiked glass-fiber filter (10-cmdiameter) instead of being injected into the mixing chamber. The mixing chamber was removed and the spiked filter was inserted into the standard PS-1 holder in front of the PUF-adsorbent cartridges. The mixing chamber with its prefilter assembly was reattached to scrub laboratory air entering the system. Seventeen collection experiments were run at air volumes of 285-380 m3, Sixteen of the runs used duplicate front and back cartridges containing 5-6 g of Tenax between PUF slices, the other run used 10 and 3 g in the front and back traps. Chlorophenols used were 2,4-dichlorophenol (2,4-DCP), 2,62,4,6-TCP, and DCP, 3,4DCP, 2,4,5-trichloropheno1(2,4,5-TCP), 2,3,4,5-tetrachlorophenol (2,3,4,5-TeCP). Chlorophenol standards were made from reagent-grade compounds that were purchased from chemical supply houses and used without further purification. The amounts used for collection experiments ranged from 0.077 to 23 r g (Table I). Analytical Methods. Analytes were extracted from intact adsorbent cartridges using 15% EE-PE in a specially designed Soxhlet apparatus built by the University of South Carolina glass shop. The solvent was concentrated by flash evaporation at room temperature to about 10-20 mL, transferred to graduated centrifuge tubes, and evaporated to 5 mL with nitrogen that had been filtered through Tenax-GC. Chlorophenols were separated from base-neutral compounds and derivatized for analysis by gas chromatography (GC) using the following procedure, adapted from Chau and Coburn12and Abrahamsson and Xie? The sample extract (5 mL) was shaken for 3.0 min with 5.0 mL of 0.1-0.2 M NaZC03 in a 16- X 125-mm culture tube having a polytetrafluoroethylene-linkedscrew cap. The phases were separated, and the organic layer was saved for the analysis of base-neutral compounds (e.g., chlorobenzenes, HCHs, aromatic hydrocarbons). The aqueous layer was skaken with 2 mL of hexane, and the hexane was added to the baseneutral fraction. A 1-mL aliquot isoocante was added to the tube containing the aqueous phase, 50-200 pL of acetic anhydride was added, and the tube was immediately capped and shaken for 3.0 min. This step (extractive acetylation) derivatized the chlorophenolsto their corresponding acetates and extracted them into the organic layer for GC analysis. For each collection experiment, an isooctane solution containing the target chlorophenols was derivatized in the same manner as the sample extracts and used as an external standard. GC analysis using a63Ni electron capture detector (GC-ECD) was carried out on Carlo Erba 4160 or Varian 3700 chromatographs. A 25-m bonded phase fused-silica column (polydimethylsiloxane, 5 % phenyl) was used for chlorophenolacetate analysis. Samples were injected splitless (Grob technique, 1-2-pL volume, 30-s split time) using the following program: Inject at 65 O C , hold 1.0 min, program at 7 "C/min to a final temperature of 260 OC. Other GC conditions were as follows: carrier gas, H2 at 3040 cm/s; injector 240 OC; detector 320 "C. Chromatographic data were collected and processed with a Hewlett-Packard 3390A or Shimadzu Chromatopac CR3A integrator.
RESULTS AND DISCUSSION Analytical Method a n d Blank Values for Chlorophenols. T o evaluate analyte losses during extraction and evaporative concentration steps, phenols containing 2-4 chlorines were spiked onto Tenax-GC in paper thimbles or PUF-Tenax-GC traps and Soxhlet extracted with 15% EEPE. The spiked compounds showed recoveries of 83-95% (Table 11). The effect of acidity on chlorophenol acetate yield was evaluated over a pH range of 4.6-9.7. The equilibrium pH (12) Chau, A. S. Y.; Coburn, J. A. J. Assoc. Off. Anal. Chem. 1974,57, 389-393. (13) Abrahamsson, K.; Xie, T. M. J.Chromatogr. 1983,279,199-208.
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Table 11. Recovery of Chlorophenols from Spiked
Adsorbents.
~
comDd 2,6-DCP 2,4-DCP 3,4-DCP 2,4,6-TCP 2,4,5-TCP 2,3,4,5-TeCP
Tenax (3 g) in paper thimbles* recovery quantity ( % mean (bbul) sd)d 0.51 91f5
*
0.48 0.97 0.23
94 i 5 95 f 12
0.11
93f 3
93f2
PUF-Tenax trapsc recovery quantity (% mean (ue) + ad) 0.51-3.1 83+ 14 0.48-2.9 85 + 20 0.52-5.9 87 + 18 0.23-1.4 86+16 84 + 12 0.24-18.6 0.11-0.64 84+ 27 ~
~
a 50 - 150 p L of acetic anhydride used. b n = 5. n = 9; except for 2,4,5-TCP where n = 7. d sd = standard deviation.
(pH of the aqueous phase following the extractive acetylation) was adjusted by changing the concentration of the NazCO3 solution from 0.1 to 1.0 M. A 5-mL aliquot of each Na2C03 solution was spiked with chlorophenols, 1 mL of isooctane, and 100 pL of acetic anhydride. Normalized acetate yields relative to the maximum yield for each compound are shown in Figure la. Overall yields of chlorophenol acetates were best at pH 4.6-6.0 and remained above 75% through the entire pH range for 2,4-DCP, 3,4-DCP, and 2,4,5-TCP. A slight reduction to 70% for 2,3,4,5-TeCP yields was observed at pH 9.3-9.7. The production of acetates was greatlyreduced at 9.3-9.7 for 2,6-DCP and 2,4,6-TCP. The chlorophenols with substitution in the 2,6-positions were more sensitive to pH effects. In the acetylation reaction both chlorophenol and water compete for the acetic anhydride. For successful derivatization to occur, the acetylation rate must be fast compared to the hydrolysis rate of acetic anhydride. The 2,6-position chlorophenols may be sterically hindered in their ability to react with acetic anhydride. An additional experiment was run using the previous conditions, except that the amount of acetic anhydride was increased to 200 pL. Increasing the acetic anhydride resulted in a lower equilibrium pH for the solutions and a pH range of 4.0-8.3. Normalized acetate yields (Figure lb) were good throughout the entire pH range with results ranging from 0.74 to 1. The equilibrium pH was 4.5-4.7 for all collection runs. Analytical blanks (cleaned and stored adsorbent traps) for PUF-Tenax-GC were
