Anal. Chem. 1997, 69, 1113-1118
GC/FT-IR/MS Spectroscopy of Native Polychlorinated Dibenzo-p-dioxins and Dibenzofurans Extracted from Municipal Fly-Ash Silvano Sommer, Ralf Kamps, Stefan Schumm, and Karl F. Kleinermanns*
Institute of Physikalische Chemie and Elektrochemie I, Heinrich Heine University of Du¨ sseldorf, Universita¨ tsstrasse 26.43.02, 40225 Du¨ sseldorf, Germany
A number of native polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were isolated from the fly-ash of a municipal waste incinerator by Soxhlet extraction. Spectroscopic analysis of seven PCDDs and 10 PCDFs by GC/MS analysis coupled with FT-IR spectroscopy was performed. For assignment of vibrations, some representative IR spectra were simulated by ab initio calculations at the Hartree-Fock level with the basis set 3-21G(d,p). The utility of GC/FT-IR/MS spectroscopy for congener analysis and isomer discrimination in native dioxin samples is discussed. A lot of work concerning the infrared analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) (see Figure 1) has been published in the last 20 years.1-13 These investigations treat specially prepared samples without recognizing the fact that native samples often show different characteristics due to their individual matrices, which may influence analytical investigations,14,15 (cf. Experimental Section). The present article deals with native PCDDs and PCDFs * To whom correspondence should be sent. E-mail:
[email protected]. (1) Grainger, J.; Reddy, V. V.; Patterson, D. G., Jr. Appl. Spectrosc. 1988, 42, 643-655. (2) Wurrey, C. J.; Fairless, B. J.; Kimball, H. E. Appl. Spectrosc. 1989, 43, 13171324. (3) Grainger, J.; Reddy, V. V.; Patterson, D. G., Jr. Chemosphere 1989, 18, 981988. (4) Grainger, J.; Reddy, V. V.; Patterson, D. G., Jr. Chemosphere 1989, 19, 249254. (5) Grainger, J.; Reddy, V. V.; Patterson, D. G., Jr. Appl. Spectrosc. 1990, 44, 41-46. (6) Grainger, J.; Reddy, V. V.; Patterson, D. G., Jr. Appl. Spectrosc. 1988, 42, 800-806. (7) Wurrey, C. J.; Bourne, S.; Kloepfer, R. D. Anal. Chem. 1986, 58, 482-483. (8) Gurka, D. F.; Brasch, J. W.; Barnes, R. H.; Riggle, C. J.; Bourne, S. Appl. Spectrosc. 1986, 40, 978-991. (9) Grainger, J.; Gelbaum, L. T. Appl. Spectrosc. 1987, 41, 809-820. (10) Holloway, T. T.; Fairless, B. J.; Freidline, C. E.; Kimball, H. E.; Klo ¨pfer, R. D.; Wurrey, C. J.; Jonooby, L. A.; Palmer, H. G. Appl. Spectrosc. 1988, 42, 359-369. (11) Gurka, D. F.; Billets, S.; Brasch, J. W.; Riggle, C. J. Anal. Chem. 1985, 57, 1975-1979. (12) Mosoba, M. M.; Niemann, R. A.; Chen, J. T. Anal. Chem. 1989, 61, 16781685. (13) Pohland, A. E.; Yang, G. C. J. Agric. Food Chem. 1972, 20, 1093-1099. (14) Sommer, S. Photooxidation of polychlorinated dibenzo-p-dioxins on fly-ash. Ph.D. Dissertation, Heinrich-Heine-University of Du ¨sseldorf, Germany, 1996. (15) Kamps, R. Photoreduction and catalytic degradation of polychlorinated dioxins and photooxidation of polychlorinated furans on fly-ash. Ph.D. Dissertation, Heinrich-Heine-University of Du ¨ sseldorf, Germany, 1996. S0003-2700(96)00884-0 CCC: $14.00
© 1997 American Chemical Society
Figure 1. Numbering system for dibenzo-p-dioxin and dibenzofuran.
extracted from municipal fly-ash by extensive cleanup procedures and analyzed by GC/FT-IR/MS spectroscopy. Our intention was to investigate the possibilities of detection and identification of dioxin and furan isomers by GC/MS analysis coupled with FT-IR spectroscopy. Because of the uncertain assignment of a number of dioxin vibrations given in the literature, some selected dioxins and furans were calculated on the ab initio level. After scaling of the frequencies with one common parameter, the simulated spectra were in reasonable agreement with the measured ones and allowed a definite assignment of the most important vibrations. EXPERIMENTAL SECTION The examined fly-ash was prepared by an extensive cleanup procedure as described in ref 16. After Soxhlet extraction of the fly-ash with toluene for 48 h, the extract was prepared for analysis by column chromatography with benzene and a hexane/dichloromethane mixture to elute the PCDD/Fs. Before extraction of the fly-ash, known amounts of 13C12marked, laterally chlorinated dioxins and furans were added as internal standards. To determine the loss rate of PCDD/Fs during the cleanup procedure, a known amount of a second “recovery standard” was added after the extraction procedure and for comparison with the initially added quantification standard, which experiences the same loss rate as the native samples. Average recovery rates were 60%. To obtain FT-IR spectra, it was necessary to concentrate the samples. The final extracts of the samples contained nearly 3 g/L PCDD and 2.4 g/L PCDF and had to be handled with care due to the extremely high toxicity. Infrared detection limits were around 10 ng of PCDD and 20 ng of PCDF. Identification and analysis were performed on a Hewlett Packard system consisting of a GC 5890 Series II gas chromatograph coupled with a split/splitless injector, a mass detector (MSD 5971), and a Fourier transforn infrared spectrometer (IRD 5965 (16) VDI guideline 3499, paper I.
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Figure 2. Schematic setup of the GC/FT-IR/MS system. Table 1. Comparison of Experimental and Theoretical IR Absorption Frequencies of 2,3,4,6,7,8,9-Heptachlorodibenzo-p-dioxin wavenumbers (cm-1) vibrations C-H stretch phenyl ring bend-stretch C-O-C antisymmetric stretch C-H in-plane deformation CdC ring bend-stretch C-O-C symmetric stretch C-H out-of-plane deformation CdC aromatic torsion and deformation C-Cl stretch C-Cl deformation
this work
ref 3
2933 1595, 1554, 1449, 1423, 1395, 1336, 1292, 1243 1243, 1203 1198 1144 967, 842
Gaussian 92 (HF/3-21G(d,p)
1650, 1559, 1480, 1454, 1428, 1398, 1334 1297 1256 1148 998, 972 848
992, 892, 811, 708, 596
