Anal. Chem. 1991, 63, 1217-1221
Environmental Protection, Trenton, NJ, for providing the aquatic biota samples from Elizabeth, NJ. Note Added in Proof. After submission of the paper, we learned that apparently the same compounds have been discussed in some meeting abstracts that were not included in general data bases (22,231.
LITERATURE CITED (1) ~Rappe,C. En&. Sd. Tedwrd. 1984, 18, 78A-90A. (2) WHOIIPCS. pdychlorhated Mbenzepdbxlns and Dibenzofurans; E n v l r o n m l Health Crlterla. 88; Waid Health Organization: Gsneva, 1988. (3) WHOIEURO. Dbxins and Furans from Mvliclpal Incinerators: Environmental Health Serbs, 17: Wwld Heatth Organlzation: Copenhagen, 1987. (4) WHOIEURO. PCBs, PCDDs, and PCDFs: Preventbn and Control of Accihtlal and Envkonmentai Exposures; Environmental Health Serbs. 23: Waid Health Organization: Copenhagen. 1987. (5) WHOIEURO. PCL, PCDDs, and PCDFs In Breast Milk: Assessment of Health Rtekr: Envkonmental Health Serles. 29; Waid Health Organization: Copenhagen, 1988. (8) WHOIEURO. Lev& of PCBs, PCDDs, and PCDFs In Breast Mlik; Envlronmentai Health Serles, 34; World Health Organlzatlon: Copenhagen, 1989. (7) Charles, M. J.; Tondeur, Y. Envkon. Scl. Technd. 1990. 24, 1.R5&lRRO -- . -. (8) Reher, E. J.; Scheilenberg, D. H.; Taguchl, V. Y. fnvkon. W. Technol. 1PBl. 25. .- - ., - , 110-117. (9) ~ v o c o o i ,0. W.; Mitchum, R. K.; Tondew, Y.; Munslow, W. D.; Vonnahme, T. L.; Donnelly, J. R. Bkmed. En&. Mbss Specbwn. 1988, 15, 669-678.
- --
1217
(IO) Heglund, P.; Egeb&Ck, K.-E.; Janseon, B. chemasphere 1988, 17, 2129-2140. (11) Buser, H. R. Envkon. Sol. Technol. 1980, 20, 404-408. (12) Bum, H. R.: KjeLr, L.Q.; Swanson. S. E.; Rappe, C. Envkon. Scl. Technol. 1989, 23, 1130-1 137. (13) Rappe, C.; Bergqvist, P.-A.; Kklkw, L.Q.; Swanson, S. E.; Belton, 1.; Ruppei, B.; Lockwood, K.; Kahn, P. C. chemoephere,in press. (14) Buser, H. R.: Reppe, C. Chsmosphers 1979, 18, 157-174. (15) Buser, H. R.: f n v l w , . HeeRh pbrspect. 1985, BO, 259-267. (16) Hale, M. D.; Hikman, F. D.; Mazer, T.: Shell, T. L.: Noble, R. W.: Brooks, J. J. A M I . chem.1081, 57, 840-848. (17) Buser, H. R.: Rappe. C. ChtWm@we 1978, 17, 199-211. (18) Buser, H. R.; Rappe, C.; Bergqvlst, P.-A. €n&m Heem Perspect. 1985, 60, 293-302. (IS) Bum, H. R.; A M / . chem.1986, 57, 2801-2806. (20) Lundgren, K.: Rappe, C.: Buser, H. R. Chetnosphm, In press. (21) Hiker, D. R.: Aldous, K. M.; Smith, R. M.: OKeefe, P. W.: Cwerty, J. F.; Juusik, J.: Hlbblns, S. W.; Splnk, D.: Parllb, R. J. c/m" 1985, 14, 1275-1284. (22) Peterman, P. H.; Smith, L. M.; Stallng, D. L.: Pew, J. D. Identification of chlorinated blphenylenes and other pdycyciic aromatlc compounds formed from the incineration of PCWlelectric Rukh at a capacitor plant's dbposal site. Proceedinps of the 34th Annual Conference on Mass Spectrometry and Allied Topics, Clncinnatl, OH, June 8-13, 1986 pp 486-487. (23) Peterman, P. H.: Lebo, J. A.; Major, H. J. Accurate mass determlnatbns of polychlorinated dlbenzothkphenes in sdi from a capacitor plant's Incineration site. Proceedbrgs of the 36th Annual Conference On Mass SpsCtrOmetry and Allled Topics, San Francisco, CA, June 5-10, 1988: pp 240-241.
RECEIVED for review December 3,1990. Accepted March 28, 1991.
Identification of Wood Species by Ion Mobility Spectrometry A. € Lawrence* I. Trace Vapour Detection Section, Institute for Aerospace Research, National Research Council Canada, Ottawa, Ontario, Canada K1A OR6
R. James Barbour and Roger Sutcliffe Forintek Canada Corp., 800 Montreal Road, Ottawa, Ontario, Canada K l G 325
Chemlcai bnlzatlon Ion mobHIty spectrometry (CI-IMS) was used to characterize a nunbar d wood specks. A rapld test procedure was developed, based on the thermal release of vapors from heartwood samples followed by IMS analysls, wtth resutts belng obtalned In 5-10 8. Reduced moblltty constants ( K O )(or the mod a@Mcanl peaks wwe cakdated, and m e of the Ions produced were matwanslyzed by lnjectlon Into a quadrupole mass spectrometer. The results of thk study point to the potential of IMS as a qualttatlve tool for the rellable Identlflcation of certaln wood specles In an Indurtrlal setting. Some results related to computer-alded curve resolution of IMS spectra are also presented.
The rapid identification of wood from different species of trees by technological means is a significant objective of a recent development effort undertaken for the Canadian forest products industry. On-line separation of logs, lumber, and other wood products by species would allow the exploitation of value-added markets as well as help to improve process control in the industry. The heartwood and outer bark of trees often contain chemicals such as hydrolyzable and condensed tannins and 0003-2700/91/0363-1217$02.50/0
many other phenolics, alkaloids, resins, essential oils, and specialized compounds that are capable of protecting these metabolically inactive tissues against biological attack (1-3). These chemicals, generally known as extractives or exudates, can be removed with inert solvents such as ether, benzenealcohol, and hot or cold water, In some cases, their presence can be correlated with a specific property of the wood such as decay resistance or color ( 2 , 4 - 6 ) ,and in certain species, they can be used as chemotaxonomic markers (2, 3, 7-9). A number of methods have been suggested to identify wood species by elucidating the presence of a specific extractive or group of extractives. These include chemical color tests (9, IO-12), pH measurements (13,14),Fourier transform infrared spectroscopy (15), and UV laser-excited fluorescence (16). While a number of these methods have been successful under laboratory conditions, they are not suitable for field use and no industrial electromechanicalsystem based on any of these methods has yet been devised. Visual identification of logs and lumber is used commerically for a number of species, but this method is somewhat subjective, prone to errors due to worker fatigue, and does not lend itself to integration into automated sorting and handling systems. Ion mobility spectrometry (IMS), also known as plasma chromatography (PC), is a relatively new analytical technique 0 1991 Amerlcan Chemical Society
1218
ANALYTICAL CHEMISTRY, VOL. 63, NO. 13, JULY 1, 1991
that distinguishes molecular species on the basis of the mobility of their ions under an applied electric field in an inert gas at atmospheric pressure (17,18). Like the electron capture detector (ECD), the ion mobility spectrometer is an ambient pressure ionization detector, and it has been used for the characterization of trace vapor constituents in gaseous mixtures (17, 18). The major advantages of IMS are its good detection limit (sub parts per billion) and fast response time (0.1-10 8 ) ; a drawback is its moderate resolution compared to other advanced separation techniques. Given these advantages and limitations, IMS is well suited for the initial screening and fingerprinting of samples in situations where time constraints dictate a short analysis cycle. Furthermore, the instrument operates at atmospheric pressure, thus eliminating the excessive hardware associated with vacuum technology and permitting miniaturization and use in rapid, on-site chemical detection (19, 20). The utility of IMS in providing a rapid, qualitative analytical technique for trace organics without the need of special sample preparation has been reported recently for a number of application areas: explosives in air (211,drug residues on the hands of overdose victims (221, screening of commerical pharmaceuticals (23). This paper describes a method for the identification of wood species that involves a simple, rapid procedure: thermal release of extractives from wood samples, followed by analysis using IMS, with results being obtained in 5-10 s. The species examined in this study were selected because of their commercial importance. They were divided into five groupings representing the species likely to be processed together in Canadian sawmills within a given geographic region. These groupings were eastern spruce, pine and fir (SPF), western SPF, eastern pine, western interior, and western coastal. Any viable method should be capable of identifying all the species within a t least one of these groups. Several issues with respect to the feasibility of the method are addressed in this study. These include determination of IMS signatures from heartwood and sapwood of 14 Canadian softwood species as well as the effects of wood decay and weathering on IMS signatures. Some of the ionic species responsible for the characteristic peaks in the IMS signatures are also identified by GC/MS and IMS-MS.
EXPERIMENTAL SECTION Wood and Chemical Samples. Two-hundred fifty samples of heartwood and sapwood were obtained from Canadian wood products companies in the form of 30-cm bolts (log segments). These samples were selected to represent the entire geographic range of each species. Heartwood and sapwood samples were collected for the following species groups: eastern SPF includes white spruce (Picea glauca (moench) Voss), red spruce (Picea rubens Sarg.), black spruce (Picea mariana (Mill.) B.S.P.), jack pine (Pinusbanksiana Lamb.), and balsam fir (Abies balsamea (L.) Mill.); western SPF includes interior spruce (Picea engelmannii Parry,Picea glauca (moench)Vow, and hybrids of the two), lodgepole pine (Pinuscontorta var. latifolia Engelm.), and alpine fir (Abies lasiocarpa (Hook.) Nutt.); eastern pine includes eastem white pine (Pinusstrobus L.) and red pine (Pinusresinosa At.);western coastal includes coastal Douglas fir (Pseudotsuga menziesii (mirb.) Franco), amabilis fir (Abies amabilis (Dougl.) Forbes),Sitka spruce (Picea sitchewis (Bong.)Carr.), and westem hemlock (Tsuga heterophylla (Raf.)Sarg.); western interior includes western SPF and interior Douglas fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), western larch (Larir occidentalis Nutt.), and western hemlock. All species were identified microscopically by using standard methods (2). Weathered samples of red pine and eastern SPF were gathered from the log yard of a Forintek member mill. Decayed wood samples of jack pine and balsam fir were collected from several mills. All wood samples were ground to pass a 1-mm screen and were stored at -10 OC. Todomatuic acid was obtained from Dr. D. Zinkle (United States Forest Products Laboratory, Madison, WI). The methyl
Table I. Instrument Parameters parameter
value
Ion Mobility Spectrometer (Phemto-Chem 100) cell length 14 cm drift length 8 cm carrier gas (purified air) 200 mL/min 600 mL/min drift gas (purified air) inlet and drift temp 220 "C drift voltage k2700 V dwell time 20 ps/channel gate width 0.2 ms delay time" 6.0 ms no. of scans 256 pressure atmospheric Ion Mobility Spectrometer-Mass Spectrometer (Phemto-Chem MMS 160) cell length 15 cm drift length 5 cm carrier gas (purified air) 200 mL/min drift gas (purified air) 600 mL/min drift voltage k2700 V inlet and drift temp 200 O C dwell time 20 ps/channel gate width 0.2 ms mass spectrometer pressure 6 X 10" Torr scanning speed lo00 amu/s Time between gate opening and start of data collection. ester (juvabione) were prepared by reaction with diazomethane. Pinocembrin, chrysin, pinobanksin, and dihydroquercetin were obtained from Dr.E. P. Swan (Forintek Canada Corp. Vancouver, BC) and were used without further purification. Instrumentation. The IMS data presented in this paper were obtained with a Phemto-Chem 100 ion mobility spectrometer (PCP Inc., West Palm Beach, FL). The signal from the IMS was averaged with a Nicolet 1170signal averager. The analog-bdigital converter (ADC) resolution used with the Nicolet was always 12 bits, and the full-scale volt setting was kept at f4 V. The basic measurement in this study was the drift time, which can be measured to f0.02 ms as determined experimentally and from which the reduced mobility constant KOcan be calculated according to KO = d / tE( 273/ 2') ( P / 760) (1) where d = drift length (8cm), t = drift time (s), E = electric field gradient (V/cm), T = temperature (K), and P = pressure (Torr). Mass identification of ions giving particular mobility peaks was achieved with a Phemto-Chem MMS 160 ion mobility spectrometer-mass spectrometer. The experiments consisted of a 3-fold approach. First, the totalion mobility spectra were obtained by gating the shutter grid of the ion mobility spectrometer cell and allowing the ion mobility electrometer to collect data; under these conditions,the quadrupole mass filter is not used. Second, mass spectral data were obtained by holding the grid of the ion mobility spectrometer cell open, thus allowing all ions formed to drift through the tube and into the mass spectrometer. Finally, mass-identified ion mobility spectra were recorded by gating the shutter grid of the IMS cell as in the first procedure but with the mass spectrometer tuned to a specific m/z value; in this case, the detector responds to only one ionic species and, consequently, the mobility spectrum contains one peak that corresponds to that ion. The experimentalparameters used to operate the ion mobility spectrometer and the ion mobility spectrometer-mass spectrometer are presented in Table I. Resolution of partially overlapped IMS peaks was achieved by transferring the digital data from the signal averager to an IBM AT compatible personal computer and a SUN workstation (Sun Microsystems Inc., Mountain View, CA); mathematical differentiation (up to the sixth derivative) was then performed in the time domain by using several Fortran 77 programs (24) as well as the MatLab Software package (MathworksInc., Sherbom,MA). Sample Injection Technique. One or two wood meal particles (-0.1-0.2 mg) were inserted into a narrow probe (10 cm long X 0.3 cm 0.d. glass tube) that had a restriction and a silanized glass
ANALYTICAL CHEMISTRY, VOL. 63, NO. 13, JULY 1, 1991
4
1218
a
ll
A /"""
Figuro 2. (a) Negative ion mobility spectrum of kdgepok pine heartwood; (b) positive ion mobility spectrum of alpine fir heartwood. I
a
I
I
I
WvllWEInrc)
PI
Flguo 1. (a) Negative bn mobility spectrum of jack pine heartwood; (b) positive ion mobility spectrum of balsam fir heartwood.
wool plug located about half-way along ita length to prevent any solid particles from entering the ion mobility spectrometer. A carrier gas stream of purified air was passed through the probe, and subsequently,the latter was inserted in the heated inlet of the spectrometer. Upon sample injection, the volatile chemicals evaporated and were flushed by the carrier gas into the ion reaction chamber of the instrument. Authentic samples of juvabione, pinocembrin, pinobanksin, cluyain, and dihydmquercetin were injected into the spectrometer by depositing 1 pL of standard solution (- 1 X lo4 g/pL in methanol) on the glass wool plug in the probe, evaporatingthe solvent with the carrier gas stream, and then inserting the probe into the heated inlet of the spectrometer. A similar approach was used to obtain ion mobility spectrometer-maea spectrometer data. Gas Chromatography/Mass Spectrometry. A sample desorption apparatus previously described (25)was used to desorb and trap high boiling point compounds from wood meal samples on the inner walls of a syringe needle prior to injection into the GC/MS apparatus. A desorption temperature of 250 O C was applied to the sample tubes for 2-3 min. Transfer of the trapped vapors into the capillary column was achieved by conventional septum injection into the heated injection port of the gas chromatograph. A Finnigan 1020 gas chromatograph/mass spectrometer was used,and the chromatographic conditions were as follows: column, DB-1,30m X 0.2 mm i.d.; carrier gas, helium at 0.6mL/min, oven temperature, 150-250"C at 5 "C/min; injector temperature, 250
"C.
RESULTS AND DISCUSSION IMS Signatures of Heartwood Samples. ZMS Signatures of Eastern SPF. A large number of analyses were made of the black spruce, jack pine, and balsam fir (eastern SPF) heartwood samples. All pine and fir samples gave unique IMS peaks at KO= 1.29 and 1.38 cm2V-' s-', respectively, the pine signature being obtained in the negative mode and the fir signature in the positive mode; representative spectra are shown in Figure 1. The spruce samples displayed only broad unresolved peaks in the region of KO= 1.00-1.10 cm2V-' s-'. Thus, given a sample known to be spruce, pine, or fir, the actual identity of the sample can be deduced by monitoring the peaks at 1.29 and 1.38. The reproducibility among similar samples was excellent, and different wood meal particles from the same sample produced identical spectra. Although care was taken not to saturate the instrument with the test compound (saturation is defined as the total depletion of reactant ions), saturation did not lead to a shift in the mobility of the target ions. The relative standard deviation of KOfor the 1.29 and 1.38 ions from 10-20 samples was typically 50.1%. Furthermore, storage of samples a t -10 O C for a period of several months did not affect the resulta. Neither spurious peaks nor changes in the IMS signatures were observed.
I* I
6
D m n T W E lmel
I PI
Firpro 3. Positive ion moMlity spectra of (a)white pine heartwood and (b) red pine heartwood.
IMS analyses of benzene-ethanol extracts from heartwood samples of jack pine and balsam fir gave signatures identical with those obtained from the wood meal samples, thus confirming that the chemicals responsible for the IMS signaturea were contained in this fraction of the extractives and were not part of the cellular structure of the wood. IMS Signatures of Western SPF. Representative ion drift patterns obtained from interior spruce, lodgepole pine, and and alpine fir are shown in Figure 2. Like their eastern counterparts, lodgepole pine exhibited an intense peak at KO = 1.29 cm2 V-' s-' in the negative mode and alpine fir had a strong peak at KO= 1.38 cm2V-' s-l in the positive mode, while no distinct peak was found in either mode for interior spruce. As with eastern SPF, lodgepole pine and alpine fir can be identified by the presence of characteristic ion peaks while interior spruce can be identified by inference. ZMS Signatures of Eastern Pine. Positive ion mobility spectra for white and red pine are shown in Figure 3. White pine gives two characteristic ion peaks with KOvalues of 1.29 and 1.26 cm2V-ls-l,r espectively. In contrast to white pine, the positive IMS spectrum of red pine changes as a function of time, e.g., a time of 30-50 s was required after injection of the sample for the characteristic triplet signature shown in Figure 3b to develop. This relatively long response time can lead to saturation of the instrument and, in turn, to a clearance time of approximately 1-2 min. Such long response and clearance times would probably be excessive in an industrial setting where much shorter cycle times are required. ZMS Signuture of Dough Fir. In contrast to all other wood species examined in this study, Douglas fir exhibited inconsistent IMS signatures. In some cases, the positive ion mobility spectrum exhibited three peaks of varying relative intensities in the drift region 16-20 ms. However, sample-tosample variation was observed, and more importantly, variation within samples was also detected. In addition, the
1220
ANALYTICAL CHEMISTRY, VOL. 63,NO. 13, JULY 1, 1991
negative ion mobility spectra obtained from all the samples did not give characteristic signatures. These results indicate that the ion mobility spectrometer does not respond selectively to the vapors released at 220 OC from Douglas fir and thus restricts the usefulness of this approach for the identification of this species. Variability of Douglas fir heartwood extractives with geographical location has been previously reported (26). This does not, however, seem to be the source of the variation observed here. Samples from both coastal and interior locations gave similar signatures and had similar variability in there signatures. The results suggest that the variation may be due to chemical differences between tissue types within a sample, but this possibility was not pursued in the current study. IMS Signatures of Sitka Spruce, Interior Spruce, Red Spruce, Black Spruce, White Spruce, Amubilis Fir, Western Hemlock, and Larch. These species displayed no characteristic IMS peaks in either the positive or negative mode and, therefore, could not be identified by this method. IMS Signatures of Sapwood Samples. No characteristic peaks were obtained from any sapwood samples examined in this study. While inner bark and sapwood are generally rich in nutrients such as fats, starch, simple sugars, and simple glycosides ( 2 ) ,they tend to be deficient in the types of extractives present in the heartwood and outer bark. The absence of these high boiling point compounds may explain the lack of an IMS response for sapwood. IMS Signatures of Aged and Weathered Heartwood Samples. The last part of this study was undertaken to determine whether the presence of decay and/or weathering would have an effect on the IMS signature obtained from the heartwood portion of a tree. In general, the occurrence of weathering and/or severe decay of the sample can lead to false identification. The peak at KO= 1.38 cm2V-' s-l was not detected from either aged or severely decayed balsam fir samples. In contrast, aged or weathered jack pine samples still exhibited the peak of KO = 1.29 cm2 V-' s-l, although often greatly reduced in intensity. GC/MS a n d IMS-MS Experiments. Initially GC/MS was used to identify thermally desorbed and trapped compounds associated with eastem SPF species. Both juvabione (I)and dehydrojuvabione (11) were detected from balsam fir. COOCH3
(1)
FOOCH3
( 11 1
These two chemicals with juvenile hormone activity have been previously isolated from balsam fir (27). Dehydroabietic acid (MW 300) and other abietic acid derivatives were detected from jack pine, whereas linoleic acid (MW 280) and transneoabienol (MW 290) were found to be present in black and white spruce. IMS-MS results for balsam fir and alpine fir showed that the peak at KO= 1.38 cm2V-' s-l is composed of two ions, m / z 207 and 205 (cf. Figure 4). These ions are formed by loss of a methoxycarbonyl radical from the molecular ion of juvabione and dehydrojuvabione, respectively. The above results were further confirmed by analyzing an authentic sample of juvabione (todomatuic acid methyl ester). The characteristic peak for jack pine and lodgepole pine a t KO = 1.29 cm2 V-l s-l was shown to have m / z 255, which can be formed by loss of a proton from the molecular ion of pinocembrin. This was confirmed by analyzing authentic
20'
0
DRIFT I ~ U i m Ew
20
-4. poslthre ion "y SpednwTl (a)and" Mdspectral data (b and c) for balsam fir heartwood.
samples of pinocembrin (III), chrysin (IV), and pinobanksin (V). These compounds normally present in jack pine ex-
HO
0
( Ill ) X = H (M.W = 256) ( V ) X = OH (M.W = 272)
HO
0
( IV ) (M.W = 254)
tractives (28)could not be detected by using GC/MS without chemical derivatization. It should be noted that a broad unresolved peak was also observed in the negative ion mobility spectrum of lodgepole pine. Mass spectral data clearly showed that this broad asymmetric peak is composed of two ions, m/z 279 and 301, which are probably formed by loss of a proton from the molecular ions of linoleic acid and abietic acid, respectively. The broad unresolved peaks from black and white spruce were shown to be due to two ions, m / z 279 and 299, which can be due to the loss of a proton from the molecular ions of linoleic acid and dehydroabieticacid, respectively. The two peaks in the positive ion mobility spectrum of white pine are produced by ions masses of 269 and 283. These compounds are probably flavones, but their exact identities were not determined. Resolution of Overlapping IMS Peaks. The occurrence of overlapping peaks in IMS is often a limitation in the detection capability of this technique (21). A number of attempts have been made to overcome such resolution problems including tandem ion mobility spectrometry (29),selective ionization techniques (21,30),and the use of some preseparation methods (e.g., GC, HPLC (31))prior to IMS sample introduction. The application of postdetection computational techniques to assess the "purity" of IMS signals has been recently reported (24,32,33). In this approach, mathematical differentiation is used as a resolution enhancement technique, to facilitate the detection and location of partially overlapped peaks in a two-component IMS signal. Figure 5 illustrates the efficacy of the application of the second and sixth derivative algorithms on the resolution of the m/z 205 and 207 ion peaks of balsam fir. In the use of the above algorithms, the IMS signal is initially fed to a low-pass filter to remove the out-of-band noise. The filtered output is then fed to a series of differentiators and low-pass filters to obtain the nth derivative (24). Unless such low-pass filters are used, the signal-to-noise ratio would be degraded as a result of the noise
ANALYTICAL CHEMISTRY, VOL.
63. NO. 13, JULY 1, 1991
1221
LITERATURE CITED
17
l7d
%8
Wd
10
DRIFT nyE (meme)
Flguro 5. PosIUve ion mobility spectra of balsam fir heartwood: (a) filtered zeroorder; (b) second derlvative; (c) sixth derivative.
enhancement produced by the differentiation process. Work is currently in progreas to combine a number of peak detection algorithms, e.g., cross-correlation,higher order derivative, etc., in order to improve both the detection limit and the resolution in IMS. CONCLUSION The results of this study indicate that the fast thermolysis/IMS analysis technique described herein is feasible for the identification of certain wood species. The method provides near real-time performance and, given the development of some automated sampling technique, lends itaelf to integration with on-line industrial process control systems. The detection and location of poorly resolved IMS peaks in a two-component signal are made possible through the application of mathematical differentiation in the time domain. Nonetheless, the single most valulable feature of this approach remains the ability of IMS to characterize individual chemical species in complex matrices without any prior sample preparation. ACKNOWLEDGMENT We thank Dr. L. Elias of the NRC for helpful discussions throughout this study, Mr. G. Chauret for preparation of the wood samples, and Mr. D. Miller for preparation of the benzene-ethanol extracts of jack pine and balsam fir.
(1) Hillis, W. E. Wood Extractbs and Uwk S&”e In Um I%@ and Paper Indupfr&s;Academic Press: New York, 1902. (2) Panshin, A. J.; de Zeeuw, C. Textbook of Wood Tsdnokgv; m a w Hili: New York, 1980. (3) Imamwa, H. Nahrel Roducts of Wood Plants XI; Rowe, J. W., Ed.; Springer-Veriag: Berlin, 1989. (4) &ay. V. R. J . Inst. Wood. Sci. 1981, 8, 35. (5) Sullivan. J. P. Forest. Rod. J . 1987, 17(7), 43. (6) Sullivan. J. P. Forest. Rod. J 1987, 17 (a), 25. (7) Selkei, M. K. Am. J . Bobny 1965, 52 (I), 1040. (8) Swan, E. P. Forest. Rod. J . 1968, 16(1).51. (9) Barton, G. M. Can. Forest Ind. 1973, 93 (2), 57. (IO) Kutsscha, N. P.; Sachs, I. B. cdor tests for dlfferentiatlng heartwood and sapwood In vertain softwood tree specles. Report No. 2240, 1902; United States Departmsnt of Agrlcuhe, Forest. Prod. Lab.: Madison, WI. (1 1) Fraser, H. S.; Swan, E. P. A chemical test to differentlate A M s a m biys from Akskcarpe wood. Envkon. Canada. Forest. Sew. BCMonh ly Res. Notes., 1972; Voi. 28, No. 5. (12) Miller, R. B.; Qukk, J. T.; Chrlstensen. D. J. Forest. Rcd. J . 1985. 35 f2L ,-,, 33. (13) McNamara. W. S.; Sullivan, C. E.; Hlggins. J. C. Wood. Scl. 1970. 3 (I), 48. (14) Kutscha, N. P.; Lomerson, J. T.; Dyer, M. V. Wood Scl. Tedmcf. 1978, 12, 293. (15) bia, Nauit,1990. J. Ph.D. Thesls, Faculty of Forestry, University of Brltlsh Cdum (10) Sum, S. T.; Singleton, D. L.; Paraskevopoubs. G.; Irwin, R. S.; Barbour, J.; Sutcllffe, R. Wood. Scl. Techno/.,In press. (17) P h s m chromatogrephy; Carr, T. W., Ed.; Plenum: New York. 1964. (18) Hill, H. H., Jr.; Slems, W. F.; St. Louis, R. H.; McMinn, D. G. Anal. Chem. 1990, 6 2 , 1201 A. (19) Blyth, D. A. Proceedings of the Internatbnal Symposium on Protection against Chemical Warfare Agents, Stockholm, Sweden, June 0-9, 1983; p 65. (20) Canico, J. P.; Davis, A. W.; Campbell, D. N.; Roehl, J. E.; Sima, G. R.; Spangler. 0. E.; Vora, K. N.; White, R. J. Am. Lab. ( F a W , Conn.) 1988, 18, 152. (21) Lawrence, A. H.; Neudorfl, P. Anal. Chem. 1988, 60, 104. (22) Nanji, A. A.; Lawrence, A. H.; Mlkhael, N. Z.J . Toxlcd. CNn. To&. 1987, 25 (0), 501. (23) Elceman, 0. A.; Blyth, D. A.; Shoff, D. B.; Snyder, A. P. Anal. Chem. 1990, 62, 1374. (24) Goubran, R. A.; Lawrence, A. H. Int. J . Mess. Specfr. Ion. Roc. 1991, 104, 103. (25) Lawrence, A. H. J. Chromtcgr. 1987, 395, 531. (20) Manvllle, J. F.; Rogers, 1. H. Can. J . forest. Res. 1977, 7 , 429. (27) Cerny, V.; oolels, L.; Fabler. L.; Sorm. F.; Slama, K. C o k t . Czech. Chem. Commun. 1987, 3 2 , 3920. (28) von Rudbff, E.; Sato, A. Can. J . Chem. 1983, 41, 2105. (29) Stlmac, R. M.; Cohen, M. J.; Wernlund. R. F. T a m Ion AmMy Specfromefry for Chemical Agent l%tect&n , Monnorlng and Alerm; PCP, Inc.: West Palm Beach, FL, Dec 1984; Contract No. DAAK11844-00 17. (30) Lubman. D. M.; Kronlck, M. N. Anal. Chem. 1982, 5 4 , 1540. (31) Hill, H. H., Jr.; Eatherton. R. L. J. Res. Met. Bweau. Stand. 1988. 3 . 425. (32) Roehl, J. E. Opt. Eng. 1985, 24 (0), 985. (33) Lawrence, A. H. Anal. Chem. 1989, 61, 343.
RECEIVED for review January 23,1991. Accepted March 19, 1991.
