Anal. Chem. 1995,67,442-446
Determination of Pentachlorophenol and Its Hydrocarbon Solvent in Wood, Soil, and Water by Gas Chromatography and FT-lR Spectroscopy in a Single-Sample Treatment And& Besner, Roland Gilbert,* Piem T&reauR, Louis wine,and Jean-Franqois Archambaultt lnstitut de recherche #Hydro-Qu&bec (IREQ), 1800 montee SainteJulie, Varennes, Quebec, Canada J3X 1SI
This analytical method offers a new way of measuring pentachlorophenol (PCP) in soil,wood, and water samples by gas chromatographyand its hydrocarbon solvent by ETIR spectroscopy. The distinctive feature of this method is that both the PCP and the oil are extracted from a single 1-gsample. They are first extracted from the wood or soil samples with a 1:l mixture of Freon 113and methanol using ultrasonication. An aliquot of the resulting organic phase is then added to an aqueous phase buffered at pH 9.2 with Na2HP04. The oil remaining in the organic phase is analyzed by ET-IR,whereas the PCP in the aqueous phase is acetylated by reaction with acetic anhydride, back-extractedin Freon 113,and injected into the gas chromatograph. Low-PCP-contentwater samples ( < 5&L) are a c i a e d and extracted in Freon 113,which is then added to the aqueous phase. High-PCP-content water samples (> 5 pg/L) are buffered and treated as the buffered aqueous phase. W a c t i o n recoveries for the different matrices range from 94 to 115%.The absolute detection limits (30) for PCP and the hydrocarbon solvent are respectively 28 ng and 0.1 mg for a 1-g solid sample or a 100-mLvolume of water sample. The PCP content of wood samples was compared with that obtained by neutron activation analysis and correlated with a 0.97 coefficient. The precision of the analytical method is better than 10%for both analytes. This analytical approach was succesdly applied to the radial characterization of freshlytreated poles for their PCP and oil contents. Pentachlorophenol (PCP) is widely used as a biocide in the wood preservatioh industry.’ It is dissolved in a hydrocarbon solvent such as oil and pressureinjected in the wood. The biocide-oil solution is present in the wood but also in the soil or water in the vicinity of wood-treatment plants. Also, it migrates out of the wood poles used by telephone companies and electrical utilities. In response to the environmentalproblems this creates, predictive software for evaluating the behavior of PCP and oil migrating from wood poles to the environment is under develop ment at Hydro-Quebec2 As the behavior of the PCP in the Present address: Dbpartement de Chimie, Universitk de MonhCal, P.O. Box 6128, Quebec, Canada H3C 3J7. (1) Rao, K R Pentachlorophenol: chemistry, pharmaceutical, and environmental toxicology; Plenum Press: New York, 1978. (2) Lefebvre, G.; Tessier, J.-C. Decision support systems for management of PCP migration in the environment Proceedings of the CWPA 12th Annual Meeting, Vancouver, BC, Canada, November 5-6, 1991. +
442 Analytical Chemisfry, Vol. 67,No. 2,January 75,7995
environment is closely linked to that of its hydrocarbon solvent? oil, both must be taken into account in modeling. In order to calibrate this predictive software, a series of PCP and oil measure ments in wood, soil, and water samples are required. This calls for specific detection of the PCP molecule, and the analytical method to be used should take this requirement into account, together with the need to quantify the hydrocarbon solvent. Several methods have been employed to determine PCP in the various environmental matrices. The analysis of PCP in wood is often done using elemental methods based on the chlorine content, such as X-ray fluorescence4or neutron activation analysis (NAA).5 While these methods are fast and require minimum sample preparation, their lack of specifcity for the PCP molecule gives rise to strong interference by the chloride content of the soil and water samples. Numerous other methods, including highperformance liquid chromatography (HPLC) 9-: gas chromatography (GC),10-13and flow injection analysis (FIA)14techniques, have been reported. The US. Environmental Protection Agency (EPA) also proposes method 8040 for PCP analysis by GC. These analytical techniques are capable of separatingvarious chlorinated phenols and further increase the selectivity for the PCP. The concentration levels of PCP in environmental samples are generally low, and the GC technique, with the higher sensitivity of the electron capture detector (ECD), is particularly well adapted to its analysis. However, in solid samples such as sediments, soils, or woods, the PCP has to be extracted before it can be determined by these techniques. On the other hand, not much attention has been paid to the determination of the PCP solvent, since it has no fungicidal effects and therefore has limited impact on the effectiveness of the preservative. It is generally determined using the oil and grease method of the American Public Health (3) Jackson, D. R; Bisson, D. L. J. Air Waste Management Assoc. 1990, 40, 1129-1133. (4) Kressbach, J. N.; Tang, J.; Walker, J. E. Proceedings of the 83rd Annual Meeting of the American Wood-Preservers’ Association, 1987. (5) Slau, J. F.; Meyer, J. A. Wood Sci. 1973,6 (l), 19-21. (6) Liu, M. H.; Kapila, S.; Nam, K S. J. Chromatogr, 1993,639, 151-157. (7)Goewie, C. E.; Berkhof, R J.; Maris, F. A; Treskes, M.; Brinkman, U. A. Th. Int. J. Anal. Chem. 1986,26, 305-318. (8) McDonald, K L.J. Chromatogr. Sci. 1984,22, 293-295. (9) Daniels, C. R; Swan, E. P. J. Chromatogr. Sci. 1979, 17, 628-630. (10) Lee, H.-B.; Peart, T. E.; Hong-You, R L.J. Chromatogr. 1992, 109-113. (11) Butte, W.; Walker, G.FreseniusJ. Anal. Chem. 1992, 343, 144. (12) Angerer, J.; Heinzow, B.; Schaller, K H.; Weltle, D.; Lehnert, G.Fresenius, J. Anal. Chem. 1992,342,433-438. (13) Abrahamsson, K; Xie, J. J. Chromatop, 1 9 8 3 , 2 7 9 , 199-208. (14) Rodriguez-Alcala, M.; Yanez-Sedeno, P.; Polo Diez, L. Ma. Talanta 1988, 35 (8), 601-604.
8 1995 American Chemical Society 0003-2700/95/0367-0442$9.00/0
Association (APHA) .15 In this method, a group of substances with similar physical characteristics are determined quantitatively on the basis of their common solubility in trichlorotrifluoroethane (Freon 113). To the authors' knowledge, no adaptation of this method for analyzing the PCP solvent in wood and soil samples has ever been proposed. A versatile analytical protocol which combines both the PCP and the oil determinationwas therefore needed to make it easier to trace these analytes in wood, soil, and water samples. This paper presents the development of one such protocol which offers three major advantages: (1) a single sample is used to determine both analytes, (2) manipulations with large-volume samples are avoided, and (3) the same protocol is used to determine both analytes in the various environmental matrices involved. The performance of the analytical method based on this protocol is presented. The PCP and oil concentrations in a freshly treated wood pole are characterized and compared with those of PCP obtained using NAA A final validation was obtained by establishing radial PCP and oil distributions of freshly treated poles. EXPERIMENTAL SECTION . Apparatus. A Hewlett-Packard 5890 gas chromatograph equipped with a 63Ni ECD, a split-splitless capillary column injection port operated in splitless mode, and a 7673A autosampler (Hewlett-Packard, Palo Alto, CA) were used for the PCP analysis. The injection port temperature was 250 "C, and the detector temperature was 325 "C. A fused silica capillary column was supplied by Hewlett-Packard: 25m x 0.32-mm4.d. x 0.52-pm HPUltra 2 (cross-linked 5% phenyl methyl silicone), programmed from 120 to 220 "C at 10 "C/min, with the final temperature maintained for 1 min. The carrier gas was helium at a flow rate of 2.5 mL/min. The inner surface of the liner was cleaned with 2 N nitric acid, silanized with a solution of 10%trimethylchlorosilane in toluene, washed with toluene and methanol, and dried at 100 "C. The oil was analyzed by a Nicolet 520 ET-IR spectrometer (Nicolet Instruments, Madison, WI), using a 1-cm-path length quartz cell, for the most part according to the APHA method.15 For each sample and standard measured, 32 scans were acquired in the range from 3200 to 2700 cm-', averaged, and processed. The solvent contribution was subtracted. The absorbance was obtained by constructing a straight baseline over the spectral range scanned and measuring the distance from the baseline to the peak maximum at 2930 cm-l. The NAA analyses were performed by an independent lab using a method developed by Kennedy for trace elements in polymers'6 similar to that of Slau and M e ~ e r .Ultrasonication ~ was performed using a L&R Model 7670 ultrasonic bath (Kearny, NJ) with an internal size tank of 501 x 2% x 20h ( ~ m - and ~ ) a power output of 1500W at 80 MHz, for a power density of 1W/cm2. Chemicals. Helium (99.95%) carrier gas and 5% argon/ methane ECD auxiliary gas were from Union Carbide (Toronto, Canada). 2,&Dichlorophenol, 2,3,&trichlorophenol, and 2,3,4,5 tetrachlorophenol were purchased from Fluka (Ronkonkoma,NY) , PCP from Aldrich (Milwaukee, WI), and acetic anhydride from BDH (Darmstadt,Germany). The methanol, Freon 113, toluene, (15) American Public Health Association. Method 503B. Partition-infrared method. In Standard methods for the examination of water and wastewater, 15th ed.; AI" Washington, DC, 1980. (16) Kennedy,G. G. Trace element determination in polymen ty neutron activation; ACS Symposium Series 440; American Chemical Society: Washington, DC, 1990; pp 128-134.
........................................................................................... Soil sample
Wood sample
[PCPI > 5 PWL
Buffered aqueous phase 1
Extracfim of ON
I
'
/solationof PCP
FTlR analysls
GC-ECD analysls
Figure 1. Basic steps of the analytical method.
and sodium phosphate were all purchased from Fisher (FairLawn, NJ). The PCP solvent used is manufactured by Shell Canada (Sarnia, Canada) under the label 645900. Procedural blanks of the solvents were analyzed by GC-ECD before sample analysis. Demineralized water obtained from a Milli-Q ultratration system (Millipore, Bedford, MA) was used for all experiments. The PCP and oil standards used for GC and FT-IR analyses were prepared by adding appropriate aliquots to the buffered aqueous phase (refer to Figure 1for the point of entry). Pipetted volumes of oil and PCP in solution in methanol were used. For the NAA, weighed amounts of PCP were added directly to approximately 0.2 g of ground untreated wood in polyethylene vials. Sample Preparation. A first stock of wood powder was prepared by chipping a PCP-treated red pine pole using an industrial shredder. The chips were ground in a Retsch SM1 cutting mill (Brinkmann Instruments, Rexdale, Canada) equipped with a 2-mm-mesh bottom sieve to obtain a powder, which was further homogenized using the four-quadrant method. Twenty sub-samplesof this powder were analyzed by NAA; the average PCP concentration obtained was 6.7 f 0.3 mg/g. A second stock of wood powder was prepared from untreated red pine pole samples collected with a 1.12cm-i.d.borer (Suunto, Finland). The core samples were reduced to powder in a Bel-Art Products Micre Mill (Pequannock, NJ) or, for below 20 mesh size, in a ThomasWiley intermediate mill (VWR Scientific, Montrkal, Canada) and homogenized. These stock samples were used to prepare samples for evaluating the performance of the method as compared to other methods used in private labs. The soil used in this study was a sand of fine granulometry with traces of silt and pH 8.6. RESULTS AND DISCUSSION Analytical Method. A block diagram of the analytical method is presented in Figure 1. The method as developed allows an organic phase containing both PCP and oil to be added to the buffered aqueous phase and includes a step for their isolation before analysis. The buffered aqueous phase used for the derivatization step is based on the method proposed by Abrahamsson and Xie13 for the analysis of PCP in water samples by GC. An internal standard is also added to each sample prior to extraction to correct for possible losses during the subsequent extraction, separation, and derivatization steps. Wood and soil samples are first extracted with a 1:l mixture of Freon 113 and Analytical Chemistry, Vol. 67, No. 2, January 15, 1995
443
Table I. Recovery Efficiencies of PCP and 011 Using Different Solvent Mixtures
solvent
ultrasonication time (min)
Freon 113 methanol methanol/Freon 113"
40 40 40
(I
% recovered (RSD)
PCP
Oil
92.9 (1.0) 95.5 (0.9) 98.4 (0.3)
94.8 (2.3) 82.1 (1.6) 96.3 (1.1)
Used on a wood sample ground below 20 mesh.
Table 2. Recovery Efficienciesof PCP and Oil as a Function of Time % recovered
extraction time (min)
PCP
10 20 40 60
96.1 (0.9) 96.9 (0.6) 98.4 (0.3) 98.1 (0.3)
(RSD) oil 93.4 92.2 95.2 94.4
(3.9) (1.0) (1.7) (0.9)
methanol (40 mL for a 1-g sample). For water samples where high PCP concentrations (>5 pg/L) are expected, the sample (100 mL) is buffered by addition of 2.5 g of sodium phosphate (Na2HP04). When the concentrations in the water sample are expected to be low (
