Report
F. W. Karasek Department of Chemistry University of Waterloo Waterloo, Ontario, N2L 3G1
F. I. Onuska National Water Research Institute Analytical Methods Division Burlington, Ontario, L7R 4A6
Trace Analysis of the Dioxins The case against the polychlorodibenzodioxins (the dioxins) as extreme ly toxic compounds is vividly made in "The Pendulum and the Toxic Cloud," a book written by Thomas Whiteside (1). With clarity and docu mentation he presents the data accu mulated over the past three decades on the deadly properties and effects of these compounds on human and ani mal life. A frightening picture evolves of humans exposed to a class of com pounds that are toxic at the parts-permillion to parts-per-billion level and carcinogenic, teratogenic, and muta genic at the parts-per-billion to partsper-trillion level. Dioxins are found as trace contami nants in a number of industrial chemi cals. A clearly defined source of diox ins is in the huge production of pentachlorophenol (PCP), of other chlorophenols, which are widely used as wood preservatives, and also in the production of herbicides, insecticides, and defoliants containing esters of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). More recent attention to the dioxins has been generated by the publicity on the long-term effects from human exposure in Vietnam to Agent Orange (a 50:50 mixture of 2,4,5-T and 2,4-D), which contains dioxin as an impurity, as well as on their presence at the Love Canal site in New York, and at the industrial plant explosion in Seveso, Italy, which spread high concentrations of dioxins over a large populated area. An added environmental concern has resulted from recent discoveries that dioxins are generated in significant amounts by incineration processes. It is difficult to evaluate the toxic, teratogenic, mutagenic, and carcino genic properties of the dioxins as they affect humans. Much of the data con cern one specific dioxin with four chlorine atoms in a group of 75 related dioxin compounds. One must extrapo 0003-2700/82/0351-309AS01.00/0 © 1982 American Chemical Society
late effects anticipated for humans from animal studies in which different animal species exhibit greatly differ ing responses. Other information is derived from observations resulting from accidental human exposure. In these cases uncertainties exist not only about the exact quantities and species of dioxins and associated chemicals involved, but also about the health histories of the subjects. Per haps the most important factor to consider is that the exact identity of the specific dioxins involved in early studies may be in doubt. Even though these studies were well conducted, the analytical methodology needed to deal with such complex and isomeric mix tures at such trace levels has only re cently been developed and is still evolving and being perfected. Widespread interest in dioxins has given rise to a number of very useful reports and reviews that summarize and evaluate our knowledge about the environmental hazards of, analytical methods for, and results of toxicological experiments for the dioxins. A group of specialists has assembled a comprehensive report containing criti cal evaluations of dioxin sources and
their effects on humans and the envi ronment (2). A companion report is devoted to an appraisal of analytical methods (3). Dioxins from combustion sources are treated in a specialized re port to which many experts have con tributed (4). Analytical methods de veloped and used by the Environmen tal Protection Agency (EPA) have been described (5), and a review of the mass spectrometry of the dioxins con tains a wealth of information of ana lytical use (6). Analytical Problem Is Complex The polychlorinated dibenzo-pdioxins (PCDDs) are a series of com pounds formed by chlorine atom sub stitution on the dibenzo-p-dioxin nu cleus.
Because of the different substitution positions possible, 75 isomers exist (see Table I). The dioxin considered the most deadly and studied the most is the 2,3,7,8-tetrachloro isomer
Table 1. Molecular Formula, Molecular Weight, and Number of Isomers of PCDD Chlorinated dlbenzo-p-dtoxfn
Total number of Isomers
Molecular formula
Molecular weight
Monochloro (MCDD)
O12H7CIO2
218.0133
2
Dlchloro ( D C D D )
O12H6CI2O2
251.9744
10
Trichloro ( T 3 C D D )
C12H5CI3O2
286.2865
14
Tetrachloro ( T C D D )
Οΐ2''4θΐ4θ2
319.8965
22
Pentachloro ( P 5 C D D )
C12H3CI5O2
353.8577
14
Hexachloro (H6CDD)
O12H2OI6O2
387.9592
10
Heptachloro (H7CDD)
C12HCI7O2
421.7799
2
C12CI8O2
455.7410
1
Octachloro (OCDD)
ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY
1982 ·
309 A
Table II. Acute Lethality of PCDD(2) Isomeric PCDD, CI position
2,8 2,3,7 2,3,7,8
LD50 (pg/kg), guinea pig
300 000 29 000 1
1,2,3,7,8
3
1,2,4,7,8
1 125
1,2,3,4,7,8
73
1,2,3,6,7,8
100
1,2,3,7,8,9 1,2,3,4,6,7,8 1,2,3,4,6,7,8,9
100 7 200 4 X 10 6 (mice)
(2,3,7,8-TCDD), which is only one of 22 isomers having four chlorine atoms. Detection of 2,3,7,8-TCDD illustrates a difficult aspect of the total analyti cal problem. Toxicological experi ments with animals have produced only limited data from the few differ ent dioxins studied to indicate that the acute toxic and carcinogenic prop erties of each group of dioxins, and in dividual isomers within a group, can vary considerably (see Table II). For the higher chlorinated dioxins, the 2,3,7,8 substitution configuration seems to be associated with the most toxic properties. This makes it neces sary to detect a specific isomer from a large group of compounds having al most identical physical and chemical properties. In addition to the analyti cal problem, one can readily appreci ate the huge effort required to synthe size all 75 dioxins and determine the toxicological properties of each. Environmental concern generates much of the demand for analytical work. The dioxins in such samples are found in complex matrices of air, water, particulate matter, and biologi cal tissues, from which the organic fraction containing the dioxins must be extracted. Because of the extremely low concentrations involved, the ex traction procedures must be efficient and nondiscriminatory and must be followed by a concentration step. Once isolated in a form suitable for analysis, the dioxins will usually be present in a complex organic mixture containing several hundred compounds. In many instances these other organic com pounds will be present at much higher concentrations and will also interfere with the specific analytical method used for the dioxins. These interfer ences must be removed by cleanup or instrumental procedures. Finally, analytical methodology for dioxins must take into account the wide spectrum of analytical services needed. Industrial quality control usu
Figure 1. Range of application of some analytical techniques for dioxins. The se lected-ion monitoring mode of GC/MS is the most applicable
ally requires detection of only a few specific dioxins in the presence of a reasonably pure chemical—a simple matrix. When survey or screening data are needed, only a semiquantitative indication of the presence of dioxins or of selected isomers is required. For this purpose methods must be rapid and involve fairly simple procedures and instrumentation. At the other end of the spectrum are those studies for which detection and quantitation of all the dioxins present are desirable. Here the methods involved are neces sarily more lengthy and require more complex instrumentation and proce dures. Analytical methodology can also be categorized by the level of isomer-specific trace detection sought. When the picogram, or parts-per-trillion, level is needed, the difficulty of analysis in creases by many orders of magnitude over that needed for the microgram, or parts-per-million, level. Figure 1 illus trates the detection ranges of applica ble analytical techniques. Radioimmunoassay Provides Screening
The radioimmunoassay method is intended primarily for preliminary screening of a large number of samples for the presence or absence of dioxins. The method does not give identifica tion of individual dioxins. Since isomer-specific methods are quite timeconsuming and elaborate, this prelimi nary screening procedure is very use ful for eliminating negative samples. The procedure is not complex. We separate the dioxin-containing frac tion of the sample from the bulk ma trix with a suitable solvent. The ex tract is purified chromatographically to reduce extraneous organic com pounds to 1 μg per sample. The puri fied residue is solubilized by Bonifica tion in a detergent-buffer mixture and incubated with a previously optimized dilution of antiserum containing rab
310 A · ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
bit antibodies. We then add radiola beled derivative of trichlorodibenzop-dioxin in an amount three times greater than that which can be bound by the antibodies. Incubation of this mixture is continued until binding is complete. An optimum amount of goat antiserum is then added, which pre cipitates the rabbit antibodies con taining the bound dioxins. After pre cipitation is complete, we centrifuge the samples, separate the supernatants, and radioassay the residue in a 7-counter. The presence of dioxins in the sample extract results in de creased radioactivity being precipitat ed relative to procedural blanks. The decrease is a measure of the amount of dioxins present in the extract. E C D / G C Gives More Specific Detection
When calibration with dioxin stan dards is done, gas chromatography with electron capture detection (ECD/ GC) is capable of giving a quantitative analysis for specific dioxins through their retention and response behavior (7). A major limitation is that the sample must not contain interfering electron-capturing compounds. This limits use of this method to those sam ples for which suitable cleanup meth ods can be devised, or to those sam ples whose original composition is so simple that interferents are absent or at low concentrations relative to the dioxins. ECD/GC provides a simple and rapid screening method. The performance of ECD/GC great ly improved in 1975 when the con stant-current, variable-frequency pulse mode of operation was intro duced with its wide dynamic range. With compounds that strongly cap ture electrons response is very nonlin ear with concentration. For accurate analysis, separate calibration for each compound and for each set of operat ing conditions is required.
Figure 2. ECD relative response as a function of temperature expressed as ratio of integrated GC peak area to area of 1,2,3,4-TCDD peak shows temperature programming is feasible
Good chromatographic results can be obtained at the 50-pg level for a standard solution of mono- through tetra-dioxins. To achieve these kinds of results it is essential that the entire GC system be functioning well. In addition to a well-conditioned, low-bleed wall-coated open tubular column (WCOT), one must use low-bleed septa to avoid introduction of spurious peaks. To improve GC peak shape and speed up analysis, temperature programming operation is very useful. However, one must be certain of the response of the compounds as the temperature changes. Figure 2 gives data on the response of several dioxins as a function of temperature. The constancy of these plots shows that temperature programming with PCDD compounds is feasible. Potentially, high-resolution gas chromatography (HRGC) with WCOT columns is capable of separating all 75 PCDD compounds through the proper choice of column coating and operating conditions. Buser and Rappe have studied the separation of all 22 TCDD isomers on glass WCOT columns with mass spectrometric detection (8). Using the three different stationary phases, Silar 10C, OV-17, and OV-101, conditions were found that allowed an assignment of retention time to most of these isomers, although no one column could completely separate all 22. Figure 3, which illustrates the results obtained, shows that the Silar 10C column allows the greatest number of isomers to be assigned unambiguously, including the extremely toxic 2,3,7,8TCDD. Several environmental samples were analyzed for 2,3,7,8-TCDD to demonstrate applicability of these columns. Work of this type is very important to reach the ultimate goal of
Figure 3. Mass fragmentogram of a composite sample showing elution of all 22 TCDD isomers on 55-m Silar 10C WCOT column. Note that this column separates the 2,3,7,8TCDD (8)
complete and isomer-specific analysis of all the dioxins. HRGC/LRMS Study of Dioxins from Garbage Incineration The dioxins all have strong, characteristic mass spectra with intense molecular ions. Since they can be well separated by gas chromatography, the GC/MS technique using high-resolution GC (HRGC) and low-resolution MS (LRMS) appears ideal for obtaining complete and specific analyses of these compounds. This technique can best be described by discussing its application to an important problem: analysis of dioxins generated by burning garbage in municipal incinerators. A Dow Chemical research team conducted an extensive study on the dioxins in which analytical procedures were developed, primarily those of HPLC cleanup followed by GC/MS analysis. The researchers analyzed samples from a wide variety of sources. Dioxins were found on particles from incineration sources, vehicle mufflers, fireplaces, cigarette smoke, and charcoal-broiled steaks (9). They concluded that formation of dioxins is a universal result of combustion of organic mixtures through trace chemical reactions occurring in fire. Some of their findings have been confirmed by others; some have not. Many large cities throughout the world dispose of their municipal waste by incineration in large plants. Many installations use the heat generated to produce energy. The city of Paris, France, derives most of its electrical and steam heating needs from three large urban waste incinerators. The major by-products of these incinerators are those fine particles formed in the combustion zone, which would
314 A · ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
enter the atmosphere with the stack gases if they were not precipitated electrostatically and collected as fly ash. Incineration of one million tons of waste produces about 35 000 tons of fly ash, 1-2% of which escapes to the atmosphere with the stack gases. The amount of urban waste incinerated worldwide each year is huge. A few estimates illustrate this: Canada, 1.5 million tons; U.S., 10-20 million; city of Paris, 1.6 million. In 1977, Hutzinger first reported finding significant amounts of dioxins adsorbed on precipitated fly ash samples from several municipal incinerators in the Netherlands. Since then we at Waterloo have examined fly ash samples from France, Japan, the Netherlands, and Canada. Evidence of the presence of most of the PCDD at high parts-per-billion levels has been found in each fly ash sample analyzed, regardless of the type of garbage, the design of the incinerator, or the detailed composition of the mixture of more than 400 organic compounds found adsorbed on the particles (10). The GC/MS instrumentation (HP 5992 bench-top quadrupole GC/MS) and the analytical procedure used are simple. The fly ash sample (~20 g) is extracted with 200 mL of benzene; the extract is condensed to 100 ML and then subjected directly to GC/MS analysis. A survey of the mass spectra associated with each GC peak reveals spectra that can be recognized as those for dioxins of each chlorinated species (Figure 4). The data in Figure 5 are more specific. By plotting above the reconstructed chromatogram the mass chromatograms of molecular ions for each isomeric species of dioxin, we reveal the presence of these species. Quantification for total amounts of
Coal Structure
TCDD ι ι ι W " i ' l " i \ 1-1- ΙΊ-ι f r ' l
".i^gg'*·'"""'"
50
100
Λ
Ι ι > ι Ι'ΙΤ-Γ^-Τ-ΓΤΤ ι ι ι ΓΙ ι ι ι
150 200 250
500 550
mlz
Advances in Chemistry Series No. 192 Martin L. Gorbaty, Editor Exxon Research and Engineering Company
I I I I I 1 I I I I
300 350 400 450
Figure 4. Mass spectra, taken at the tops of GC peaks in a GC/MS analysis of an organic extract from an Ontario incinerator fly ash, show well-defined spectra with intense molecular ions for each isomeric group of dioxins
K. Ouchi, Editor Hokkaido University Based on a symposium sponsored by the Division of Fuel Chemistry of the Ameri can Chemical Society. An excellent treatment of research on this important source of electricity and synthetic fuel. This 22-chapter volume focuses on the organic, inorganic, and physical structure of coal. Following an introductory over view of coal science, the advances in ap plying new spectroscopic techniques to gain a better understanding of coal struc ture are examined. This book will be of continuing interest and use to all coal and analytical chemists who are presently conducting research on coal structure. CONTENTS Coal Structure and Coal Science · Average Aromatic Ring Size · Labeled Guest Molecules in Coal · Nature of the Free Radicals in C o a l s · Ή NMR Absorption in Coal and Pitch «Applica tion of " C . 2 H . ι Η NMR and GPC to the Study of Structural Evolution of Subbituminous Coal · Coal Structure and Thermal Decomposition Products · Carboxylic Acids and Coal Structure • Lignin-Like Polymers in Coals · Short-Time Reaction Products of Coal Liquefaction · Characterization of Hydrolytically Solubilized Coal · Chemistry of Acid-Catalyzed Coal Depolymerization · Structure of Brown Coal by Reaction with Phenol · Alkylation of Coal · Re ductive Alkylation of Coal · Organic Sulfur Functional Groups · Chemical Structure of Heavy Oils Derived from Coal Hydrogénation · Reagent Access and the Reactivity of Coals · Sorption Studies · Particulate Structure in Alkali-Treated Brown Coal · Ultrafine Structure of Coal · Iron-Bearing Minerals in Coal 376 pages (1981) LC 80-24104
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'.Figure 5. Data from a GC/MS analysis of fly ash extract show the reconstructed chromatogram and mass chromatograms for each group of dioxins. Using charac teristic molecular ions for each isomeric group, some individual isomers and their associated GC peaks are clearly seen in this complex mixture. These data were obtained using a packed column and temperature-programmed run each isomeric group can be done using reference standards and mass chro matograms. However, the selected-ion monitoring (SIM) mode of GC/MS op eration gives higher sensitivity and a broader range of applicability (see Figure 1), since the mass spectrometer only detects a few selected ions rather than scanning an entire spectrum. It is necessary for SIM data to confirm that the peaks represent the dioxins, and not similar compounds that just happen to have the same retention times. We obtain a confirmation from
316 A · ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
data in Figure 6, which show ions characteristic of the TCDD. This fig ure also shows that corresponding peaks in the different traces have the same intensity ratios as are observed in mass spectra of TCDD. The WCOT column produces 14 defined GC peaks instead of the seven obtained on a packed column (Figure 5). One can analyze the extract of these samples for dioxins without prior cleanup be cause the dioxins are at relatively high concentrations and interfering com pounds are either not present or are at
Figure 6. SIM plots of four characteristic ions in the TCDD mass spectra can be used to confirm identity of TCDD isomers by coincidence and by proper intensity ratios. The sample and GC conditions were the same as seen in Figure 6 except that a 50-m WCOT column was used. Peaks corresponding to retention times of TCDD standards are marked
EPA procedure (13). Using quality assurance samples, a mean percent accuracy of ±23% for 1- to 1250-pg TCDD was attained. The criteria one must satisfy to give confirmation of the presence of 2,3,7,8-TCDD in a sample are listed in Table III. To appreciate the complexity and care needed in this analysis, we will give a summary of the procedure. TCDD analyses are done at the Canadian National Water Research Institute using methodology similar to that of the EPA (14). The instrumentation is a Varian MAT 311A mass spectrometer interfaced to a Varian 2700 gas chromatograph equipped with a 30-m X 0.25-mm i.d. OV-1 WCOT glass column with a separations capability of 100 000-150 000 effective plates. The instruments are directly interfaced with a 0.2-mm i.d. fused silica capillary. The procedure begins with the tuning of the MS magnet current to the mlz 318.9793 ion of perfluorokerosine (PFK) and the adjustment of the mass resolution to the 6000-10 000 range. We monitor the electrical sector field voltage and use it to calculate the acceleration voltage required for TCDD masses 327.8847 (Ci2H 4 0 2 37 Cl 4 ), 321.8936 (C 12 H 4 02 35 Cl3 37 Cl), and 319.8965 (Ci 2 H 4 0 2 35 Cl 4 ), which are
Figure 7. WCOT column GC/HRMS multiple-ion-selection chromatogram obtained from an extract of fish tissue: (a) sample; (b) sample fortified with 3 CI 4 -TCDD and TCDD quantification standard. The sample was fortified with 150 pg of 37 CI 4 -TCDD. Four parts-per-trillion of 2,3,7,8-TCDD were detected. Resolution of mass spectrometer was 6800
used for the SIM analysis. A 2-/uL volume of TCDD quantitation standard (mixture of 125 pg/VL of 37C14-TCDD and 5 pg^iL 2,3,7,8-TCDD in benzene) and 0.5 yuL of n-tetradecane is injected into the column. The run is made isothermally at 80 °C for 6 min, then temperature programmed to 240 °C at 34 °C/min. We optimize MS sensitivity for a source pressure of 5 X 10~6 torr using the mlz 319 ion of PFK, and initiate SIM analysis 16 min after injection to record the 2,3,7,8TCDD ions at a retention time of 20 min ±5 s. To obtain a quantitative measure of TCDD in a sample, we obtain peak height measurements for the mlz 320, 322, and 328 ions of 37 C1 4 /TCDD. Then, we fortify the sample with a 37 C1 4 /TCDD internal standard and repeat the peak height measurements. The residue level and detection limit for 2,3,7,8-TCDD are determined from these data. One can obtain percent recoveries of 37C14-TCDD, which measure extraction and cleanup efficiencies, by spiking the sample before extraction. Typical concentrations of quantitation standards are 50-300 pg/ML for 37 C1 4 -TCDD and 1-5 pg//tL for native 2,3,7,8-TCDD. The 37C14-TCDD percent recovery value can be used to cor-
320 A · ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
rect the TCDD residue value and limit of detection for recovery losses. Data and results are seen in Figure 7. For samples from highly contaminated sources this procedure must include measurement of the TCDD ions of mlz 256.9327 and mlz 258.9298, which are ions formed from the specific loss of COCI from the parent molecule. All this, to obtain a single result, may seem overly complicated. But a number of factors make these steps mandatory. One is the difficulty of reproducibly separating isomers whose mass spectra and GC retention are almost identical, making the labeled internal standard necessary. Another factor is that at the picogram level, irreversible and variable adsorption of sample and standards can occur on surfaces of glassware and on all parts of the GC/MS system. There is also the matter of interferences. Even after cleanup procedures, the dioxin-containing fraction could still have compounds present at equal or greater concentrations whose mass spectra contain interfering ions. In many cases MS resolution of 12 00018 000 is required to separate interfering ions. At the moment, it appears that multiple ion high-resolution SIM is the only unequivocal method for such pi-
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Table III. Criteria Utilized for Confirmation of 2,3,7,8TCDD Residues ( 13) 1. Correct WCOT GC/HRMS retention time of 2,3,7,8-TCDD 2. Correct chlorine isotope ratio of the molecular ion (ml ζ 320 and ml ζ 322) 3. Correct WCOT GC/HRMS multiple ion monitoring response for TCDD masses and 37 CI-TCDD mass (simultaneous response for elemental composition of ml ζ 320, ml ζ 322, and ml ζ 328) 4. Correct response for coinjection of sample fortified with 37 CI-TCDD and TCDD standard 5. Response of ml ζ 320 and ml ζ 322 must be greater than 2.5 times noise level
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Supplemental criteria that may be applied to samples from highly contaminated sources: 1. COCI loss indicative of TCDD structure 2. WCOT GC/HRMS peak-matching analysis of ml ζ 320 and ml ζ 322 in real time to confirm the TCDD elemental compositions
cogram analyses, but high-resolution mass spectrometers are complex and expensive, and they suffer a loss of sensitivity with increasing resolution. There is need for more research on both high- and low-resolution SIM techniques for picogram analyses. At best, TCDD analysis is allowing envi ronmental scientists to work down to 0.1-pg levels for short periods of time. To go below this level will require a thorough understanding of the adsorptive properties of the entire sys tem and of preparation of standards, calibration of syringes, and availabili ty of labeled isomers. Although in principle HRGC promises complete separation of isomers, perhaps that will never be achieved. Then, for lowlevel TCDD analyses it will be manda tory to develop tailored cleanup pro cedures to effectively remove interfer ing compounds. Newer Techniques Show Promise Newer techniques that have been applied to dioxin analysis are negative chemical ionization, atmospheric pres sure ionization (API), and the tandem mass spectrometer system (MS/MS) (15,16). Of these the MS/MS system shows the most promise for providing sensitive and selective analyses. An
(9) Bumb, R. R. et al. Science 1980,210, 385. (10) Eiceman, G. Α.; Clement, R. E.; Karasek, F. W. Anal. Chem. 1979,51, 2343. (11) Karasek, F. W.; Clement, R. E.; Viau, A. C. J. Chromatogr:, in press. (12) Karasek, F. W.; Clement, R. E.; Sweetman, J. A. Anal. Chem. 1981,53, 1050 A. (13) Harless, R. L.; Oswald, E. O.; Wilkin son, M. K.; Duprey, A. E.; McDaniel, D. D.; Tai, H. Anal. Chem. 1980, 52, 1239. (14) Onuska, F. I.; Comba, M. E.; Thomp son, R. "Mass Spectrometric Capabilities for Determination of Tetrachlorodibenzo-p-dioxins"; CCIW Report: Bur lington, Ontario, December 1979. (15) Mitchum, R. K.; Moler, G. F.; Korfmacher, W. A. Anal. Chem. 1980, 52, 2278. (16) Yost, R. Α.; Enke, C. E. Anal. Chem. 1979,57,1251 A. (17) "Detection of Dioxin Using the TAGA 6000 MS/MS System," Application Note 5881-A; SCIEX: Thornhill, Ontario, Oc tober 1980.
Figure 8. Forty picograms of 1,2,3,4-TCDD monitored at the parent ion and at two of the daughter ions; the response at the same masses of much larger amounts of PCB and DDE, two common interferences in other techniques. The absence of a response at the two daughter ions from more than a 1000-fold excess of the PCB and DDE demonstrates the ability of this technique to detect TCDD in the presence of excess amounts of these species ( 17) M S / M S system with an A P I source has been used to analyze for T C D D c o m p o u n d s with little effect from interferents p r e s e n t (17). M S / M S p e r m i t s selectivity of a u n i q u e n a t u r e . Ions are selected by a first q u a d r u p o l e m a s s analyzer, frag m e n t e d by ion-molecule reactions in a second q u a d r u p o l e m a s s analyzer, a n d t h e fragments (daughter ions) are mass analyzed by a t h i r d q u a d r u p o l e mass analyzer. T h u s , molecular ions from two c o m p o u n d s of masses so close as not to be separable a t t h e res olution used will give fragment ions of different m a s s a n d s t r u c t u r e after t h e ion molecule reactions. T h e t h i r d q u a drupole m a s s analyzer can be t u n e d to d a u g h t e r ions indicative of a specific parent. W i t h c o m p u t e r control of t h e system, different m o d e s of operation of t h e first a n d t h i r d m a s s analyzers yield highly selective information. T h e d a t a seen in Figure 8 show n o t only picogram sensitivity, b u t t h a t detection of T C D D is possible in t h e presence of large a m o u n t s of interfering P C B c o m p o u n d s by using responses of t h e T C D D d a u g h t e r ions. At these T C D D daughter-ion masses, n o P C B d a u g h ter ions occur. T h e analytical applica tions of this M S / M S system have n o t been extensive, b u t it is already evi d e n t t h a t u l t r a t r a c e d e t e r m i n a t i o n of various organic p o l l u t a n t s could be achieved w i t h o u t tedious c l e a n u p pro cedures. Although M S / M S i n s t r u m e n tation is commercially available, its high complexity a n d cost (~$500 000) are real barriers to its analytical use. F u r t h e r research is now being con
d u c t e d on m a n y p h a s e s of solving t h e p r o b l e m s associated with m a k i n g these vital analyses. It will require a b r o a d - b a s e d effort, b u t it is h o p e d t h a t t h e results will be applicable to other p r o b l e m s . Similar to t h e dioxins in toxicity a n d chemical s t r u c t u r e , t h e chlorodibenzofurans are found also on all o u r incinerator fly a s h s a m p l e s . T h e i r isomeric d i s t r i b u t i o n leads t o a series of 135 c o m p o u n d s , p r e s e n t i n g an even greater challenge for analysis. References (1) Whiteside, T. "The Pendulum and the Toxic Cloud"; Yale University Press: New Haven, Conn., 1979. (2) National Research Council of Canada. "Polychlorinated Dibenzo-p-dioxins: Criteria for Their Effects on Man and His Environment"; NRCC publication No. 18574; National Research Council of Canada: Ottawa, December 1981. (3) National Research Council of Canada. "Polychlorinated Dibenzo-p -dioxins: Limitation to the Current Analytical Techniques"; NRCC publication No. 18576; National Research Council of Canada: Ottawa, December 1981. (4) American Society of Mechanical Engi neers. "Study on State-of-the-Art of Dioxins from Combustion Sources"; ASMS, United Engineering Center: New York, N.Y., 1981. (5) Tiernan, T. O.; Taylor, M. L.; Erk, S. D.; Solch, J. G.; Van Ness, G.; Dryden, J. "Dioxins: Analytical Method for In dustrial Wastes"; EPA-600/2-80-157; EPA: June 1980; Vol. II. (6) Mahle, N. H.; Shadoff, L. A. Biomed. Mass Spectrom., in press. (7) Bruner, F. In "Electron Capture— Theory and Practice"; Zlatkis, A; Poole, C. F., Eds.; Elsevier: Amsterdam, 1981; pp 241-54. (8) Buser, H. R.; Rappe, C. Anal. Chem. 1980, 52, 2257.
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Francis I. Onuska (top) received his doctorate under J. Janak in Brno, Czechoslovakia, in 1969. For the past eight years he has headed a GC/MS analytical laboratory at the Canadian National Water Research Institute in Burlington, Ontario. His current re search activities are in environmental trace analytical chemistry, involving development of improved instrumen tation and methodology with an em phasis on toxic organic pollutants in water, sediment, fish, and wildlife. Francis W. Karasek teaches analyti cal and instrumental courses at the nearby University of Waterloo. His research interests and activities coin cide with those of Onuska, and the two are active collaborators.
