F. W. K a r a s e k Department of Chemistry University 01 Waterloo Waterloo. Ontario, N2L 3G1
ReDort
F. 1. Onuska National Water Research Institute Analytical Methods Division Burlington. Ontario, L7R 4A0
Trace Analysis of the Dioxins The case against the polychlorodibenzcdioxins (the dioxins) as extremely toxic compounds is vividly made in “The Pendulum and the Toxic Cloud,” a book written by Thomas Whiteside (I).With clarity and documentation he presents the data accumulated over the past three decades on the deadly properties and effects of these compounds on human and animal life. A frightening picture evolves of humans exposed to a class of compounds that are toxic a t the parts-permillion to parts-per-hillion level and carcinogenic, teratogenic, and mutagenic a t the parts-per-hillion to partsper-trillion level. Dioxins are found as trace contaminants in a number of industrial chemicals. A clearly defined source of dioxins 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-trichlorophenoxyaceticacid (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 5050 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 a t 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 carcinogenic properties of the dioxins as they affect humans. Much of the data concern one specific dioxin with foul chlorine atoms in a group of 15 related dioxin compounds. One must extrapo0003-2700/8210351-309A$01.0010
0 1982 American Chemical Scciety
late effects anticipated fur humans from animal studies in which different animal species exhibit greatly differing responses. Other information is derived from observations resulting from accidental human exposure. In these cases uncertainties exist not only about the exact quantities and sDecies of dioxins and associated c‘hemicals involved, but also about the health histories of the subjects. Perhaps the most important factor to consider is that the exact identity of the specific dioxins involved in early studies may he in doubt. Even though these studies were well conducted, the analytical methodology needed to deal with such complex and isomeric mixtures a t such trace levels has only recently 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 critical evaluations of dioxin sources and
their effects on humans and the environment ( 2 ) .A companion repon is devoted lo an appraisal of analytical methods (31. Dioxins from combustion sources are treated in a specialized report to which many experts have contributed ( 4 ) . Analytical methods developed and used by the Environmental Protection Aaencv (EPAJhave been described A d a review of the mass spectrometry of the dioxins contains a wealth of information of analytical use (6).
e),
Analytical Problem Is Complex The polychlorinated dibenzo-pdioxins (PCDDs) are a series of compounds formed by chlorine atom suhstitution on the dihenzo-p-dioxin nucleus. C l x f & O p 0
Because of the different substitution positions possible, 15 isomers exist (see Table I). The dioxin considered the most deadly and studied the most is the 2,3,7,8-tetrachloro isomer
ANALYTICAL CHEMISTRY, VOL. 54. NO. 2, FEBRUARY 1982
son A
Table II. Acute Lethality of PCDD (2) ISOmwIC
PCDD.
CI pcanh 2.8
LOsa (WlW.
w1nn .
PIP
300 000
Z3.7
29 000
2.3,7.8
1
1,2.3,7,8
3
1,2,4.7,8
1125
1,2.3.4,7.8
73
1.2.3.6.7.8
100
1.2.3.7.8.9
100
1.2,3.4,6,7.8
7 200 Y 106 (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 analytical problem. Toxicological experimenta with animals have produced only limited data from the few different dioxins studied to indicate that the acute toxic and carcinogenic properties of each group of dioxins, and individual isomers within a group, can vary considerably (see Table 11). For the higher chlorinated dioxins, the 2,3,7,8 substitution configuration seems to be associated with the most toxic properties. This makes it necessary to detect a specific isomer from a large group of compounds having almost identical physical and chemical properties. In addition to the analytical problem, one can readily appreciate the huge effort required to synthesize 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 biological tissues, from which the organic fraction containing the dioxins must he extracted. Because of the extremely low concentrations involved, the extraction procedures must be efficient and nondiscriminatory and must he followed hy 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 compounds will be present a t much higher concentrations and will also interfere with the specific analytical method used for the dioxins. These interferences 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 usu310A
e 1. Range of application of some analflied techniques for dioxins. The ieitedion 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 necessarily more lengthy and require more complex instrumentation and procedures. 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 increases by many orders of magnitude over that needed for the microgram, or parts-per-million, level. Figure 1 illustrates the detection ranges of applicable analytical techniques. Radioimmunoassay Provides Screenlng 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 identification of individual dioxins. Since isomer-specific methods are quite timeconsuming and elaborate, this preliminary screening procedure is very useful for eliminating negative samples. The procedure is not complex. We separate the dioxin-contiining fraction of the sample from the hulk matrix with a suitable solvent. The extract is purified chromatographically to reduce extraneous organic compounds to 1 fig per sample. The purified residue is solubilized by sonification in a detergent-buffer mixture and incubated with a previously optimized dilution of antiserum containing rab-
ANALYTICAL CHEMISTRY. VOL. 54, NO. 2, FEBRUARY 1982
bit antibodies. We then add radiolabeled 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 precipitates the rabbit antibodies containing the hound dioxins. After precipitation is complete, we centrifuge the samples, separate the supernatants, and radioassay the residue in a y-counter. The presence of dioxins in the sample extract results in decreased radioactivity being precipitated relative to procedural blanks. The decrease is a measure of the amount of dioxins present in the extract. ECDIGC Gives More Specific Detection When calibration with dioxin standards 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 samples for which suitable cleanup methods can be devised, or to those samples whose original composition is so simple that interferents are absent or a t low concentrations relative to the dioxins. ECD/GC provides a simple and rapid screening method. The performance of ECD/GC greatly improved in 1975 when the constant-current, variable-frequency pulse mode of operation was introduced with its wide dynamic range. With compounds that strongly capture electrons response is very nonlinear with concentration. For accurate analysis, separate calibration for each compound and for each set of operating conditions is required.
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Temperature C.C)
.
.gum 2. ECD relative response a s 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 he 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 he 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 lOC, 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 1OC 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 314 A
Fig-.- _. Mass fragmentogram c. --.nple showing elutlon of all 22 TCDD isomers on 55-m Silar 1OC WCOT column. Note that this column separates the 2,3,7.8-
TCDD (s)
complete and isomer-specific analysis of all the dioxins.
HRGCILRMS 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 GUMS 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 hy 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
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 t,ons; US.,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-hillion 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 GUMS) 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 rL 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
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315 A
Coal Structure
Advances in Chemistry Series No. 192 Martin L. Gorbaty, Editor Exxon Research and Engineering Company
Figure 4. Mass spectra, taken at the tops of GC peaks in a GClMS 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 Basedona symposiumsponsoredbythe Division 01 Fuel Chemistry of the Ameri:an Chemical Society. An excellent treatment of researchon this impltant sourceof electrlcltyand synthetic fuel. This 22-chapter volume focuses on the organic, inorganic, and physical structure 01 coal. Foilowing an intrcductory overview of coal science, the advances in applying new spectroscopic techniques to gain a better understanding of coal structure are examined This book will be of continuing interest and usetoallwai and analyticalchemists whoare presently conducting research on coal structure. CONTENTS Coal Slruclure and Coal Science *Average Aromalic Ring Soze *Labeled Guest M o l e c ~ l e ~ in Coal Nalure of the Free Radicals in Coals< 'H NMR Absorption m Coal and Pitch SApplica t i 0 n o f W *H. 'H NMR and GPCtathe Stildyot Sliuclurai Evolution of SUbbilUminOUS Coal Coal Structure and Thermal Decomposilion Produck *CarboxyllcAcids and Coal Slruclure Lylnin-Like Polymers I" Coals Short-Time Reaction Products d Coal Liquefaction Characterizationof Hydrolytically Solubilized Coal Chernislry of Acid-Catalyzed Coal Depolymerimion * Structure of Brown Coal by Reaction WIM Phenol Alkylation 01 Coal * Reductie Alkylalian of Cod Organic Sull~r Function4 Groups Chemical Structure of Heavy Oils Derived from Coal Hydrogenation Reagent Access and me Reactivity of Coals * Sorption SIudies Particulate Structure in Alkali-TreatedBrown Coal * Ultrafine Structure of Coal Iron-Bearing Minerals in Coal
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?d extra, w the analysis of 1 3ta fro chromatogram and mass chromatograms for each group of dioxins. Using characteristic molecular Ions for each isomeric grwp. some individual isomers and h i r associated GC peaks are clearly seen in this complex mixture. These data were obtained using a packed column and temperature-programmed run
Flaure
each isomeric group can be done using reference standards and mass chromatograms. However, the selected-ion monitoring (SIM) mode of GC/MS operation gives higher sensitivity and a broader range of applicability (see Figure l),since the mass spectrometer only detects a few selected ions rather than scanning an entire spectrum. It i s 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
ANALYTICAL CKMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
data in Figure 6, which show ions characteristic of the TCDD.This f i g ure also shows that corresponding peaks in the different traces have the same intensity ratios aa 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 because the dioxins are at relatively high concentrations and interfering compounds are either not present or are at
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too low a concentration to affect the results, Some informative data can be developed using this method. Fly ash particles from an incinerator in Paris have been separated into different size fractions, and the distribution of dioxins according to particle size has been determined (11).The gmaller particles show a higher concentration of dioxins than the larger for this sample. These data may give some clues concerning the mechanism of formation. In another study, a set of suirvey samples taken under different incinerator operating conditions permitted development of correlation equations relating the total amount of dioxins of each isomeric group formed to two operating variables, incineratlor combustion temperature (T in "C) ,and quantity of air admitted to the combustion zone (A in m3/h). The equation for the TCDD isomer quantity formed is: TCDD (ng/g) = 0.5011 T1/2
- 0.00031 A With these sets of equations one is able to predict dioxin Concentrations for each isomeric group for other samples from a different furnace a t the same facility. This illustrates that we can obtain valuable information with an analytical method that only gives a measure of total isomers. More studies like these are needed because the worldwide effect of dioxins from incineration could be great. The detection limit for the HRGCI LRMS technique used for the fly ash analyses is about 1 ng/gL. To obtain consistent, reproducible results one must optimize each step in the procedure. The extraction solvent must be free of artifacts, and one must take great care in the 2000-fold concentration step (12).A major problem is the need for a large number of dioxin reference standards. Only a limited number are available commercially and their toxicity complicates laboratory storage and use. Ultratrace Analysis Requires HRGWHRMS When analysis for a specific dioxin present at the low parts-per-trillion or pglg level in a complex matrix is required, elaborate procedures and complex instrumentation are needed. This type of analysis is frequently encountered for human, biological, and environmental samples and when the dioxin sought is 2,3,7,8-TCDD. In these cases several steps are involved: extraction, chemical separation, chromatographic separation, extract condensation, and HRGC/HRMS analysis using the SIM technique and an isotopically labeled (37CI)2,3,7,8TCDD internal standard. Harless has described details of these steps in the
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ANALYTICAL CHEMISTRY, VOL.. 54, NO. 2, FEBRUARY 1982
319A
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 a s seen in Figure 6 except that a 50-m WCOT column was used. Peaks corresponding to retention times 01 TCDD standards are marked
EPA procedure (13).Using quality assurance samples, a mean percent accuracy of *23% for 1- to 1250-pgTCDD 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 111. To appreciate the complexity and care needed in this analysis, we will give a summary of the procedure. TCDD analyses are done a t 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 OOO 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 m/z 318.9793 ion of perfluorokerosine (PFK) and the adjustment of the mass resolution to the 6000-10 OOO range. We monitor the electrical sector field voltage and use it to calculate the acceleration voltaee reauired for TCDD 319.8965 (C;iH;O;35CI;), which are
Flgure 7. WCOT column GCIHRMS multiple-ion-selection chromatogram obtained from an extract of fish tissue: (a) sample; (b) sample fortified with 3C14-TCDDand T C W quak tification standard. The sample was fortified with 150 pg of 37C14-TCDD.Four parts-per-trillion of 2,3,7,6-TCDD were detected. Resolution of mass spectrometer was 6800
used for the SIM analysis. A 2-pL volume of TCDD quantitation standard (mixture of 125 pg/pL of 3’CL-TCDD and 5 pg/pL 2,3,7,8-TCDD in benzene) and 0.5 pL of n-tetradecane is injected into the column. The ryn is made isothermally at 80 “C for 6 min, then temperature programmed to 240 “C a t 34 “C/min. We optimize MS sensitivity for a source pressure of 5 X 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 f 5 s. To obtain a quantitative measure of TCDD in a sample, we obtain peak height measurements for the m/z 320, 322, and 328 ions of 37CL/TCDD. Then, we fortify the sample with a Wl&”DD 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 "Cia-TCDD, which measure extraction and cleanup efficiencies, by spiking the sample before extraction. Typical concentrations of quantitation standards are 50-300 pg/pL for W14-TCDD and 1-5 pg/pL for native 2,3,7,8-TCDD. The 37Cla-TCDDpercent recovery value can be used to cor-
320A * 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 m/z 256.9327 and m/z 258.9298, which are ions formed from the specific loss of COCl 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 a t the picogram level, irreversible and variable adsorption of sample and standards can occur on surfaces of glassware and on all parts of the G C m S 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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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 environmental 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 system and of preparation of standards, calibration of syringes, and availability 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 mandatory to develop tailored cleanup procedures to effectively remove interfering compounds.
Newer Techniques Show Promise Newer techniques that have been applied to dioxin analysis are negative chemical ionization, atmospheric pressure ionization (API), and the tandem mass spectrometer Bystem (MSiMS) (15,E). Of these the MS/MS system shows the most promise for providing sensitive and selective analyses. An
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(9) Bumb, R. R. et al. Science 1980,210, 385.
‘(10)Eiceman,G . A,; Clement, R. E.; Karasek, F. W. Anal. Chem. 1979,51,2343. (11) Karasek, F. W.; Clement, R.E.; Viau, A. C. J. Chromotogr., in press. (12) Karasek, F. W.; Clement, R. E.; Sweetman. J. A.Anal. Chem. 1981.53. . . 1050 A. (13) Harleso, R. L.;Oswald. E. 0.; Wilkinson, M. K.; Du rey, A E , McDaniel, D. D.; Tai, H. .!mi. Ckek, 1580,52, 1* I O
(14) Onuska, F.I.; Comba, M. E.;Thompson. R. “Mass SpectrometricCapabilities
for Determinationof Tetrachlorodibenzo-o-dioxins”: CCIW Reoort: Burlin to;, Ontario,December i979. (15)hitchum, R. K.; Moler, G. F.;Korf%:$her. W. A. Awl. Chem. 1980.52, *L‘O.
(16) Yost. R. A.:Enke. C. E. Anal. Chem. i g n 5i,1251~. (17) ‘‘betectionof Dioxin Using the TAGA 6000 MS/MS System,” A plication Note 5881-ASCIEX Thornhifi.Ontario. Oetober l9so
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 mwe than a 1000-fold excess of the PCB Flgure 0. Forty picograms of 1,2,3,4-TCDD monitored at the parent
and DM demonstrates the ability of this technique to detect TCDD in the presence of excass amounts of these species ( 17)
MS/MS system with an API source has been used to analyze for TCDD compounds with little effect from interferents present (17). MS/MS permits selectivity of a unique nature. Ions are selected by a first quadrupole mass analyzer, fragmented by ion-molecule reactions in a second quadrupole mass analyzer, and the fragments (daughter ions) are mass analyzed by a third quadrupole mass analyzer. Thus, molecular ions from two compounds of masses so close as not to be separable at the resolution used will give fragment ions of different mass and structure after the ion molecule reactions. The third quadrupole mass analyzer can be tuned to daughter ions indicative of a specific parent. With computer control of the system, different modes of operation of the first and third mass analyzers yield highly selective information. The data seen in Figure 8 show not only picogram sensitivity, but that detection of TCDD is possible in the presence of large amounts of interfering PCB compounds by using responses of the TCDD daughter ions. At these TCDD daughter-ion masses, no PCB daughter ions occur. The analytical applications of this MS/MS system have not been extensive, but it is already evident that ultratrace determination of various organic pollutants could be achieved without tedious cleanup procedures. Although MS/MS instrumentation is commercially available, its high complexity and cost ( 4 5 0 0 OOO) are real barriers to its analytical use. Further research is now being con324A
ducted on many phases of solving the problems associated with making these vital analyses. It will require a broad-based effort, but i t is hoped that the results will be applicable to other problems. Similar to the dioxins in toxicity and chemical structure, the chlorodibenzofurans are found also on all our incinerator fly ash samples. Their isomeric distribntion leads to a series of 135 compounds, presenting 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 Dibenw-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. “PolychlorinatedDibenzo-p-dioxins: Limitation to the Current Analytical Techni ues”; NRCC publication No. 18576 &ationalResearch Council of Canada: Ottawa, December 1981. (4) American Societyof Mechanical Engineers. “Study on State-of-the-Artof Dioxins from Combustion Sources”: ASMS, United Engineering Center: New York, N.Y., 1981. (5) Tieman, T. 0.; Taylor, M. L.; Erk,
S.D.;Solch,J.G.;VanNess,G.;Dryden, J. “Dioxins: Analytical Method for Industrial Wastes”; EPA-6W12-80-157; EPA June 1980;Vol. 11. ( 6 ) Mahle. N. H.: Shadoff.L. A. Biomed. Mass Spectrom., in press. (7) Brunet, F. In “Electron CaptureTheory 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.
ANALYTICAL CHEMISTRY, VOL. 54. NO. 2. FEBRUARY 1982
Francis I. Onuska (top) received his doctorate under J.Janak in Brno, Czechoslovakia, in 1969.For the past eight years he has headed a GCIMS analytical laboratory at the Canadian National Water Research Institute in Burlington, Ontario. His current research activities are in environmental trace analytical chemistry, involving development of improved instrumentation and methodology with a n emphasis on toxic organic pollutants in water, sediment, fish, and wildlife. Francis W. Karasek teaches analytical and instrumental courses at the nearby University of Waterloo. His research interests and activities coincide with those of Onuska, and the two are active collaborators.
