Document rBnZbJQQ1kq77B565gX5kro1r

Ko. 6 ChPeemrfofaspwhoenrePNreos.s6L, tdpp. 4119579- P42r4in. ted in Great Britain 0045-6535/79/ 0601-0415*02.00/0 562 (1976). 1978) . 6 , 231 (1977). '.428 ( 1 9 7 6 ) . ;ric. Food :inger. 7 6 ). .977) . racts, oigeles , T o x i c o l t `1 FORMATION OF POLYCHLORINATED DIBENZOFURANS (PCDfjs) AND DIBENZO-p-OlOXINS (PCDDs) FROM THE PYROLYSIS OF CHLOROBENZENES , Hans Rudolf Buser Swiss Federal Research Station CH - 6820 Wdenswil, Switzerland INTRODUCTION Polychlorinated dibenzofurans (PCOFs) and dibenzo-p-dioxins (PCDDs) are two series of tricyclic aromatic compounds with similar chemical, physical and toxicological properties {for structures see below). In all, there are 75 PCOD and 135 PCDF isomers ranging from the mono- to the ootachloro compounds. Some of these compounds have J extraordinary toxic properties. Toxicity seems to depend highly on the number and position of the chlorine substituents; 2,3,7,8-tetrachlo^odibenz-p-dioxin (2,3,7,8tetra-CDD) and the corresponding dibenzofuran analogue (2,3,7,8-tetra-CDF) appear to be the most toxic isomers. :1978). ibmitted, '9 7 6 ) L965) . lfl. 15. PCDFs x-1-8 PCDDs PCDFs and PDOs were involved in several accidents and have caused severe intoxiv cations like Yusho in south-west Japan in 1968, and environmental contaminations like J that of Seveso, Italy in 1976, Until recently, .they were mainly regarded as undesired r oe N P 0W 548 783359 ! trace contaminants of certain industrial chemicals such as chlorophenols and their derivatives (phenoxy a d d s ) a n d `polychlorinated biphenyls (PCBs). However, tiey can also be formed In substantial amounts from these Industrial chemicals through pyrolytic r e a c t i o n s . ^ Furthermore, PCDFs and PCODs have been identified'in fly ash and flue gases of municipal and industrial incinerators, ** and recently it was reported that they are possibly ubiquitous products of combustion processes. 5 [| In this paper, we wish to report on the formation of PCDFs and PCDDs through pyrolytic reactions from chlorobenzenes. In model experiments using sealed quartz mini -ampoules, we show that tetra- to octa-CDF and also tetra- to octa-CDD are formed from the pyrolysis of tri-, tetra- and pentachlorobenzenes in the presence of air. In addition to PCDFs and PCDDs, chlorophenols and a series of other chlorinated compounds were formed in these pyrolyses. Since chlorobenzenes are used in fairly large quantities as solvents and as fI starting materials in a variety of chemical processes, this formation of PCDFs and PCDDs may be of some importance and the disposal of chlorobenzenes through incineration or I burning of wastes and residues from such processes should be strictly controlled in order to prevent environmental and occupational exposures from the hazardous PCDFs and PCDDs. EXPERIMENTAL The column c to 240C. The pyre mass spectre acquired mas chromatogran PCDFs and P( quantities < ranged from samples wer ether. The com separation column temf (tetra-), interfereTM and M+ , H+ (octa-) fo Compounds The following chlorobenzenes were obtained from Fluka, Buchs, Switzerland in purum or technical quality: 1,2,3-, 1,2,4- and 1,3,5-tri-, 1,2,3,4-, 1,2,3,5-j and 1 ,2,4,5-tetra-, and pentachlorobenzene. None of these chemicals contained detectable quantities of PCDFs, PCDOs, PCBs, chlorophenols, polychlorinated diphenyl ethers (PCDPEs)|, naphthalenes (PCNs) i 'I or styrenes (PCSs). Standard solutions of chlorobenzenes were prepared at concentrations of 10 rag/ml in n-hexane. Hicropyrolysis of chlorobenzenes Samples (200 ;jg) of tri-, tetra- and pentachlorobenzene were pyijolyzed at 620C in separate, sealed quartz mini-ampoules (volume 0.3 ml) in the presence of air. The exact pyrolysis conditions were as previously described. 2 In case of the ttri- and'tetrachlorobenzenes, the pyrolysis was carried out on mixtures containing equal amounts of each l1 isomer. In addition, a combined chlorobenzene sample (500 ig) containing equal amounts of each tri-, tetra- and pentachlorobenzene (7 compounds) was pyrolyzed. Afterjpyrolysis, 100 jj! of benzene was added to each sample and a 2-pl aliquot used for analysis. GC-MS Analysis A Finnigan 4000 quadrupole GC-MS instrument coupled to a 50 m Silar 10c glass capillary column (0.36 mn ID) was used. The column was interfaced to the MS via a platinum capillary. 010549 The p; quartz mil range whe chloroben that prev was requi the prese In tt decomposi benzenes combined the comp from tri' chlorobe process degree o to chior 783360 fi'.,. Bo* 6 Ho. 6 417 their ey can also lytic d flue ed that they ugh pyrolytic ampoules, we pyrolysis of CDFs and in these ts and as s and PCDDs tion or led in order and PCDDs. The colunn conditions were as follows: 100 , 2 min isothermal, 10/min to 140, 5/min to 240C. The pyrolyzed samples were analyzed for neutral compounds by recording complete El mass spectra (70 eV, m/e 35-500, 2 sec/scan) using a Finnigan 6111 data system..The acquired mass spectra were searched for specific compounds by running appropriate mass chromatograms and recalling mass spectra if required. Semi-quaritifications were made for PCDFs and PCDDs using mass chromatograms at M+ , M++2 oj M++4 after calibration with known quantities of reference compounds. The limits of detection using this mode of operation ranged from 0.03-0.1 ng/injection for the tetra- to octachloro'compounds. Some of the samples were reanalyzed for phenolic compounds after methylation with diazomethane in ether. The combined chlorobenzene pyrolyzate was reanalyzed for best PCDF and PCDD isomer fl o separation using mass specific detection (mass fragmentography) and a slower (2 /min) [+ + Mj+2 M+4 306column temperature prograimring rate. The ions monitored were or at m/e 340 374- 410 444(tetra-), (penta-), (hexa-), (hepta-) and (octa-) for the PCDFs minimizing interference from PCNs (PCDPEs that would interfere at these m}e values were not present), and M+ , M++2 or M +4 at m/e 320 (tetra-), 354 (penta-), 388 (hexa-), 424 (hepta-) and 460 (octa-) for the PCDDs. in purum or 4,5-tetra-, es of PCDFs, lenes (PCNs) centrations . 620 C in The exact ;etrachloroof each il amounts of jyrolysis, ;is. jlass capillary inum capillary. RESULTS ANO DISCUSSION The pyrolyses of tri-, tetra- and pentadi larobenzenes were carried out in sealed quartz mini-ampoules at 620 C in the presence of air. The temperature used was in the l .] 2 range where we previously observed the formation of PCOFs from PCBs. The amounts of chlorobenzenes (200-500 jjg) pyrolyzed were larger than the amounts of PCBs pyrolyzed in that previous study. The pyrolyzates of chlorobenzenes were analyzed directly; no clean-up was required and no interference in the determination of PCOFs and PCOD5 was observed from the presence of large quantities of undecomposed chlorobenzenes. In the pyrolyzed samples, chlorobenzenes were still the major components present. The decomposition was higher for the lower chlorinated species andjwas * 951 for the trichloro benzenes, ~ 90S for the tetrachlorobenzenes a n d ^ SOI for pentachlorobenzene in the combined chlorobenzene pyrolyzate. Chlorobenzenes withja higher degree of chlorination than the compounds used for pyrolysis were observed in all pyrolyzates, e.g. tetra- and pentafrom trichlorobenzenes, penta- and hexa- from tetrachlorobenzenes, and hexa- from penta chlorobenzene; these higher chlorinated benzenes must hjave beenj formed in a chlorination process from lower chlorinated congeners. The formation of chlorobenzenes with a lower degree of chlorination than the compounds used for pyrolysis was not observed. In addition to chlorobenzenes, mass spectral analyses of the pyrolyzates revealed the presence of a I GENP 010550 783361 series f other chlorinated compounds including PCOFs, PCDDs, chlorophenols and in some cases PCNs, PCSs and PCBs; PCDPEs and polychlorinated biphenylenes were not observed. Significant quantities of PCDFs and PCDDs were found In most of the pyrolyzed samples (see Tables 1 and 2). The formation of these tricyclic aromatic compounds is bimolecular; the likelihood of this formation is highly dependent on the concentration of chloro benzenes In the reaction system. In these experiments, rather high concentrations were used; the yields are expected to be-substantially smaller 1f lower concentrations were used. Cl m 0 2 ,620C Cl, Cl, x + y^ 2m Cl, Cl, As seen in Table 1, significant quantities of PCDFs were formed from the tri - and tetrachlorobenzenes and from the combined chlorobenzene sample. Tetra-, penta- and hexa- CDFs were formed from trichlorobenzenes, and hexa-, hepta- and octa-COFs from tetrachloro benzenes. Pentachlorobenzene gave only a small amount of hepta- and octa-CDF. The combined sample formed PCDFs ranging from the tetra- to the octachloro compounds] In general, the PCDFs formed had chlorine numbers of 2m-2, 2m-1 and 2m, where m is the chlorine ^number of | 'I the chlorobenzene employed. In case of the trichlorobenzenes, some higher chlorinated dibenzofurans(hepta-CDF) were alsoobserved;presumably, they are formed from higher chlorinated benzenesproducedduring pyrolysis. ' In Figure 1, mass fragmentograms of the combined chlorobenzene pyrolyzate show the l II elution of tetra-, penta-, hexa-, hepta- and octa-CDF on the 50m Silar |0c glass capillary column. A complex isomeric mixture is observed; it includes octa-CDF, ail 4 hepta-CDFs, 13 of a total of 16 hexa-CDFs, around 20 of a total of 28 penta-CDFs, and up to' 20 tetra- COFs. Many of these isomers were identified by co-chromatography with reference^ compounds; these peak identifications are given in Table 3. The complex isomeric mixture observed suggests the formation of-these PCDFs via^ several reaction routes. The known toxic isomers (2,3,7,8-tetra-, 1,2,3,7,8- and 2,3,4,7,8-penta-COF) are present but not as main components. i In case of the PCDDs (see Table 2), the amounts formed in these pyrolyses were smaller than the amounts of PCDFs observed. However, substantial amounts of PCDDs (hexaj-, hepta- and sane octa-CDD) were still observed from the tetrachlorobenzenes andj from the combined chlorobenzene sample (tetra- to hepta-CDDs). Smaller amounts of tetra- and penta-CDD were Table! : For Compounds Trichloroben: Tetrachlorobpentachlorob Combined chi a: 200 ig b: 200 jjg c: 200 <m d: 500 pc Table 2 : Ft Compounds Trichlorobe: Tetrachloro Pentachlorc Combined ch a,b,c,d obtained fr of octa-CDC show the e` given in T; and 1,2,3, In add these pyro of chlorin of the chi trichlorob phenol als Ho. 6 and in seme observed. lyzed samples bimolecular; chloroCions were cions were + y 2m tri- and a- and hexati tetrachloro- The combined jeneral, the ine number of lorinated im higher i show the lass capillary aepta-CDFs, to 20 tetraice compounds; 2 observed toxic isomers nain s were smaller axa-, hepta- the combined enta-CDD were Ho. 6 419 Table 1 : Formation of PCDFs from the pyrolysis of chlorobenzenes 1 PCDFs formed (ng/saraple) Compounds tetra- penta- hexa? hepta- Trichlorobenzenes3 r 400 1100 5501 50 octa<5 Tetrachlorobenzenes11 Pentachlorobenzenec Combined chlorobenzenes^ 2 2 80 5 160 r < 5 < 5! 600 nool 450 200 5 30 600 60 a: 200 jjg total with equal amounts of 1.2,3-, 1,2,' - and 1 3,5-trichlorobenzene b: 200 ^ig total with equal amounts of 1,2,3,4-, 1,2,3,5- and 1,2,4,5-tetrachlorobenzene c: 200 jig pentachlorobenzene d: 500 jig total with equal amounts of all tri-, tetra- andjpentachlorobenzenes (7 compounds) Table 2 : Formation of PCDDs from the pyrolysis of chlorobenzenes I) PCDDs formed (ng/sample] l Compounds tetra penta- hexa[ hepta- Trichlorobenzenes3 u Tetrachlorobenzenes 30 <2 20 < 5' <5 5 140| 160 octa<5 30 Pentachlorobenzenec d Combined chlorobenzenes 2 50 < 2 * 5| < 5 220 220! 70 5 5 a,b,c,d : explications see Table 1 i 1 1 1t obtained from the trichiorobenzenes; pentachlorobenzer e gave cnly an insignificant amount of octa-CDD. In Figure 2, mass fragmentograms of the combined chlorobenzene pyrolyzate show the elution of tetra-, penta-, hexa-, hepta- and |octa-CDD. Isomer assignments are given in Table 3. The known toxic isomers (2,3,7,8-tetra-, 1 ,2,3,7,8-penta-, 1,2,3,6,7,8- and 1,2,3,7,8,9-hexa-CDD) were present but again not as main components. In addition to PCDFs and PCDDs, other chlorinated jeompounds were also observed from these pyrolyses. All pyrolyzed samples showed the presence of|chlorophenols. The degree of chlorination of these phenols was the same and higher t h a n t h e degree of chlorination of the chlorobenzenes used: tri-, tetra- and pentachlorophenol were observed from trichlorobenzenes, tetra- and pentachlorophenol from tetrachlorobenzenes, and pentachloro phenol also from pentachlorobenzene. These chlorophenols could possibly serve as reaction iGENP 010552 783363 420 Ho. 6 l So 6 Table 3 : Identification of PCOF and PCDO isomers in the combined chlorobenzene pyrolyzate (Figures 1 and 2) Peak No. * Figure 1) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 PCDF isomer Peak No. (see Fiqure 2) PCOD isomer 1,3,6,8-tetra-CDF 1.3,7,91.3,6,71.2.4,62,4,6,82,3,6,82,3,7,8- 1,2,4,6,8-penta-CDF 1,3,4,7,91.3,4,7,81.2,4,7,81.2,4,7,91 ,2,3,7,8-+l,2,3,4,81,2,3,6,71,2,6,7,81,3,4,8,92.3,4,6,81,2,4,8,92,3,4,7,82.3,4,6,7- 1 ,2,3,4,6,8-hexa-CDF 1,3,4,6,7,81,2,4,6,7,81,2,3,4,7,81,2,3,6,7,81,2,4,6,8,9-+l,2,3,4,6, 71,2,3,6,8,92,3,4,6,7,8- 1,2,3,4,6,7,8-hepta-CDF 1,2,3,4,6,7,91,2,3,4,6,3,91,2,3,4,7,8,9- octa-CDF 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 1 ,3,6,8-tetra-l 1.3,7,91.3,7,81.3,6,72,3,7,81,3,8,91.2,7,8 1,2,4,6,8- (or 1,2.3,6,81,2,4,7,81,2.3,7,91,2,3,7,81.2.3,6,71,2,3,8,9- 1,2,4,6,7,9- (< 1,2,3,4,6,81,2,3,6,8,9- (< 1,2,3,4,7,81,2,3,6,7,81,2,3,7.8,91,2,3,4,6,7- 1,2,3,4,6,7,9-1 1,2,3,4,6,7,8- octa-CDD CDO intermediates in the formation of PCDFs and PCDDs from chlorobenzenes. A reaction of chlorophenol with unreacted chlorobenzene could lead to PCOPEs (route A, below), which are known to form PCDFs (and to a lesser degree PCDDs) upon pyrolysis.^ However, PCDPEs were not actually observed in.the samples analyzed here. Dimerization of chlorophenols is a further route to PCDDs (route B, below). The former condensation (route A) via PCDPEs may be preferred in these pyrolyses due to the initially much higher concentration of chloro benzenes present, but for a substantiation of these presumptions and to obtain a more detailed picture of the reactions involved, further work will be required. e pyrolyzate Figure V : Hass fragmentograms (50 in Sllar 10c glass capillary column, m/e 306, 340, 374, 410 and'444) showing elution of tetra-, penta-, hexa-, hepta- and octa-CDF 1n a combined chlorobenzene pyrolyzate. Peak Identifications are oo given In Table 3; experimental conditions see text. co CO en cn 1 fc Figure 2 Mass fragmentograms (50 m Silar 10c glass capillary column, m/e 320, 354, 388, 424 and 460) showing elution of tetra-, penta-, hexa-, hepta- and octa-CDD in a combined chlorobenzene pyrolyzate. Peak identifications are given in Table 3; experimental conditions are the same as in Figure 1. CL2 o o ZT+ c r Cl rc> i/i CLO n> o l O >O no o>-__ o O3QIaSJ aiA* nz r o-- 3n<CL o rt -1 o cr n> 3 M fD 3 CL 1 rr o  PCDDs Additional chlorinated compounds observed in these pyrolyses were PCNs (mainly heptaand octachloronaphthalenes) and PCSs (hepta- and octachlorostyrenes) from tetra- and penta chlorobenzenes. Smaller quantities of higher chlorinated biphenyls (PCSs) were also observed. Other chlorinated compounds, were present, some of which were tentatively identi fied as chlorinated benzofurans (M*=288, C1^ ; M**322, Cl^; major fragments M*-C0 and M+-C0C1 ) and benzonitri les (M+=273, Cl5 ; M+=239, Cl4 ). tentative 1 CONCLUSIONS In this paper, we report on the formation of hazardous PCDFs and PCDDs from the -Pyrolysis of chlorobenzenes. In our model experiments, gas phase pyrolyses of chloro- toizenes were carried out at rather high concentrations corresponding to about 1 g/lt of *'r* At lower concentrations, smaller yields of PCDFs and PCDDs are expected due to the ^molecular character of this formation. Chlorinated benzenes have been observed in emissions from municipal and industrial incinerators.3 The source of these compounds in these emissions is not completely c'ear* Chlorobenzenes can be formed from other chlorinated organic compounds including 3 t and possibly even from inorganic chloride and organic materials under pyrolytic Editions, but the amounts of chlorobenzenes obtained and the concentrations reached via routes are probably too low to represent a risk for the formation of PCDFs and 'Jr *^s* Th situation, however, may be different if attempts are made to dispose of 783367 Ho. T Chonosf P ergc technical quantities of chlorobenzenes (such as wastes and residues of industrial processes) by Incineration. In such a case, the concentration of chlorobenzenes may well reach a range where the formation of PCDFs and PCDOs is probable. Therefore, incineration or burning of chlorobenzenes should be strictly controlled in order to ensure safe disposal and to prevent environmental and occupational exposures not only to chloro benzenes but also to the hazardous PCOFs and PCDOs. ACKNOWLEDGEMENTS We thank Prof. C. Rappe, University of UmeS, Sweden, and Dr. H.-P. Bosshardt, Swiss Federal Research Station, Wadenswil, for discussion. REFERENCES 1. C. Rappe, S. Marklund, H.R. Buser and H.-P. Bosshardt, Chemosphere, 7_, 269 (1978). 2. H.R. Buser, H.-P. Bosshardt and C. Rappe, Chemosphere, 7_, 109 (1978). 3. K. Olie, P.L. Vermeulen and 0. Hutzinger, Chemosphere, 455 (1977). 4. H.R. Buser and H.-P. Bosshardt, Mitt. Geb. Lebensm. u. Hyg., 6 9 , 191 (1978). 5. Oow Chemical Company, The Trace Chemistries of Fire, Report, November, 1978. 6. R. Lindahl, C. Rappe and H.R. Buser, in preparation (1979). 7. E.S. Lahaniatis, H. Parlar and F. Korte, Chemosphere, , 11 (1977). 8. 8. Ahling, A. Bjorseth and G. Lunde, Chemosphere, 7_, 799 (1978). 9. see note in reference 3. (R e c e iv e d in UK 20 A p r il 1979) GENP 010557 Coep a r a t i by Dauter > ~ U sag (I) telo* rcbetitul a -itend to p vectc 2 - Chemi (I) Basic and p a r a t the phosp o a la th io r 3. . - CH 33 . - OC p la n t comp und, ch em ical c o n c ise ly place, e*. 3 - Persi cow c 16 . in four t; vaxer at C - Typic: residues i of dichlo: periods i: 3.35 PI 5 - Toxicc a3t0io).n aDnedla protein et and c h o lir tion to tl and/or e r index o f e 6 - Biolo 1 Dept, of J o i n t FA