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Anal. Chem. 1989, 61, 736-740
Supercritical Carbon Dioxide Extraction of Polychlorinated Biphenyls, Polycyclic Aromatic Hydrocarbons, Heteroatom-Containing Polycyclic Aromatic Hydrocarbons, and n-Alkanes from Polyurethane Foam Sorbents Steven B. Hawthorne,* Mark S . Krieger,' and David J. Miller Energy a n d Mineral Research Center, University of North Dakota, Grand Forks, North Dakota 58202
Supercrltical fluld extraction (SFE) with CO, is a rapid alternative to liquid solvent extraction for the recovery of organic air pollutants collected on polyurethane foam (PUF) sorbent plugs. Quantitative recovery (>95 % ) of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAW) ranging from naphthalene to perylene, several heteroatomcontakdngPAHs, and n-alkanes ranglng fm C,, to C,, was achieved with 10-20-mln extractions. Classselective extraction of n-alkanes versus PAHs resulted from the sequentiat extraction of the same PUF plug at 80 and 380 atm. Dlrectly coupled SFE with gas chromatography (SFEGC) allowed a PUF sample to be analyzed in go%) using COPa t 400 bar (395 atm) and 125 "C, although two species, chrysene and benzanthrone, were quantitatively recovered when methanolmodified COP was used. The present report describes the use of supercritical COz for the quantitative extraction and recovery of a variety of organic air pollutants including PAHs, heteroatom-containing PAHs, n-alkanes, and PCBs from PUF sorbent plugs. Extractions were performed by use of a simple and inexpensive extraction cell, which can be constructed from commercially available fittings in a few minutes. The extraction and analysis of a variety of organic air pollutants from PUF by using SFE and coupled SFE-GC is demonstrated for diesel exhaust, cigarette smoke, and roofing tar volatiles.
EXPERIMENTAL SECTION Polyether-type polyurethane foam (grade 3014)obtained from Olympic Products (Greensborough,NC) was cut into cylindrical plugs 2.5 cm long X 2.5 cm in diameter (ca. 0.25 g of PUF) with a hole saw. Several plugs were cleaned at once by sonicating in four changes of pesticide grade acetone, the residual solvent was evaporated from the PUF under clean air, and the plugs were stored in brown glass bottles until used. Air samples were collected onto the PUF sorbents by inserting two plugs (front and back) into a 24 mm i.d. glass tube and drawing air through the plugs at 4 L/min for 10 min with a Du Pont Model P4000 personal sampling pump. After sample collection, the PUF plugs were stored in brown glass bottles at 4 "C until they were extracted. The sample of exhaust from a diesel-powered bus was collected ca. 2 m from the outlet of the
0003-2700/S9/0361-0736$01.50/0Q 1989 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 61, NO. 7, APRIL 1, 1989 A
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Table I. Extraction of n -Alkanes, PAHs, and Heteroatom-Containing PAHs from Polyurethane Foam Using Supercritical COz % in % recovery fraction I
Figure 1. Supercritical fluid extraction cell constructed from Parker brand stainless steel flttings. Components of the cell are (A) a 1/4 in. female NPT fltting with a ' I gin. tube stub, (B) a 'I, in. diameter stainless steel frit (2 pm), (C)a 'I4 in. male NPT X '/le in. tube ftting, (D) a ' / l e in. 15% graphite/85% polyimide ferrule, (E) a in. tube ftting nut, and (F)fused sUica tubing outlet restrictor. During extractions, the tube stub end of ftting "A" was connected to the supply line from the pump.
exhaust pipe. The temperature of the exhaust plume at the collection point was ca.40 "C. Cigarette smoke was collected ca. 1/2 m above a burning menthol cigarette. Roofing tar volatiles were collected ca. 1m away from the vat used to melt the tar (i.e., approximately where the operator's face was when stirring the vat). For the recovery studies, PUF plugs were spiked by injecting a small volume (
