Document bBoB78EnENawpm21wEepagMZ

-7*- Photochcmical Degradation of Isomerically Pure Di-, Tetra-, Hexa-, Octa- and Decachlorobiphenyls 0. HUTZINGER. W. D. JAMIESON. S. SAFE Atlantic Regional Laboratory, National Research Council of Canada, Halifax, N. S. and V. 2ITK0 . Environment Canada, Fisheries Service Biological Station, St. Andrew's, N, B. We have previously shown that photochemical changes occur in chlorinated biphenyls on irradiation with a number of light sources (1,2). This report deals with the behaviour of a number of chlorobiphenyls on exposure to natural sunlight. Experimental 100 Milligrams each of 4,4'-dichlorobiphenyl (I), 3,3',4,4*tetrachlorobiphenyl (II), 2,2',5,5'-tetrachlorobiphenyl (III) and 2,2',4,41 ,5,5'-hexachlorobiphenyl (IV) were dissolved in benzene and spread evenly on a pyrex dish (diameter: 35 cm) under a gentle flow of air to ensure uniform formation of a chlorobiphenyl film. Distilled water (5 ml) was added to the dishes which were then loosely covered with plastic material to prevent dust and rain to contaminate the chlorobiphenyl film but allow air to exchange(3).Dishes were exposed, on the laboratory roof, for the period June 24 to September 15, 1971. Total duration of bright sunshine was 612 hours (4). After this period of exposure the contents of the dishes were dissolved in acetone and the solvent and residual water removed by evaporation. After weighing, the residue was redissolved in each case, streaked onto a preparative TLC plate (20 x 100 cm coated silica gel F-254) and the plate developed in hexane three times. Three bands were visible on the plates under U.V. illumination: band A at Rf 0.7-0.9 corresponding to the starting material; band B at Rf 0.4-0.7 which was usually weak and band C at the origin to approximately Rf 0.1. The bands wpre eluted with benzene-ethyl acetate (A,B) and ethyl acetate-acetone (C) with the addition of small amounts of water, the solvent removed and the crude extracts examined by mass spectrometry using a DuPont/CEC 21-110B double focussing instrument. The samples were slowly heated in the direct introduction probe and electrical scans as well as photoplate exposures obtained at different temperatures. The polar fraction C was methylated with excess diazomethane. i The main c on exposure to (a) Loss o either the star The amount of c (I); 7 mg (II); will be conduct (b) Contra of chlorine was chlorobiphenyls substrate proba produced. Unde extensive loss (chlorobiphenyl (c) A band on TLC in all c chlorine could products to be little or no ch (d) A numb other than PCB compounds whose resolution spec are being proce will be availafc 1. S. Safe ar 2. 0. Hutxinf Terspect^ 3. D. G. Cros in "Dcgrac! D. D. Kauf 4. Values fre N. S., suj Environmei OSW 030219 STLCOPCB4014181 M i". t* -75- cur ght r ,4,4'II) in ! under robiphenyl ,i were and to r the right hes er edissolved 100 cm three arting band C jted e (C) removed ga ties were ical nt oraethane. I Results ond Discussion The main conclusions for the behaviour of tbo four compounds on exposure to natural sunlight (see table) are ns follows: (a) Loss of weight occurred presumably by evaporation of either the starting material or more volatile breakdown products. The amount of crude material recovered from the dishes was 4.8 mg (1); 7 mg (II); 17 mg (III) and 34 mg (IV). Future experiments will be conducted in closed quartz tubes. (b) Contrary to irradiations in hexane where stepwise loss of chlorine was observed, irradiations in thin films producos chlorohiphenyls of higher chlorine content. In this case the substrate probably acts as scavenger ("solvent") for the Cl* produced. Under the present experimental conditions, however, extensive loss of compounds with tower vaeoov i'\vmv (chlorohiphenyls containing less chtovtnei t* tlietx. (c) A band corresponding to more polar product* w.n. ohveived on TLC in all cases. Mass spectra for definito compounds containing chlorine could not be obtained, however, which indicates the products to be either polymers or thermally labile compounds with little or no chlorine remaining. (d) A number of peaks corresponding to chlorinated compounds other than PCB were observed. Among these were terpbenyls and compounds whose compositions could not be deduced from the low resolution spectra. High resolution data from the photoplates are being processed. These data and information on other isomers will be available. References 1. S. Safe and 0. Hutzinger, Nature, 232, 641 (1971). 2. 0. Hutzinger, S. Safe and V. Zitko, Environmental Health Perspectives, 1, in press (1972). . . 3. D. G. Crosby and M. Y. Li, "Herbicide Photodecomposition" in "Degradation of Herbicides" (ed. P. C. Kearney and D. D. Kaufman), H. Dekker Inc., N. Y.; 1969; p. 321. 4. Values from Canadian Force Base Shearwater, Halifax Co., N. S., supplied by Maritimes Weather Office, Atmospheric Environment.Service. --'ffPWWWPI DSW 030220 STLCOPCB4014182 I -76- u fT, . tT wofO> -coo fO u c,*h c i4 NO* Uf _ X --- O T- Ur <0* r> (V u 0_ x / 8 (V e j--------- 1---------1--------- 1--------- Lg 8o A||tUO|U| bo o> o > O PK< >s xc: pH X) fo*oH4 XUo5j 4J--. K> K> 46MP- < *cd x> a H 44 O *J U 4) WP>e V) Vrt) 2E O 3> H U4 Mass Spectr Band A B I Cl trace C1..C /e 4 509, C and nethylated 4 Legend: Many pea) impuritif apparent, Cl* , Cl#, ctt lupinuj iuim.ivpg HWFPfMW DSW 030221 STLCOPCB4014183 F ig u re 1. Mass spectrum o f "TLC band A" from 3 ,3 ',4 ,4 * -te tra c h lo ro b ip h e n y l exposed to s u n lig h t. -77' TABLE Mass Spectral Data on Compounds Formed by Irradiation Band I Chlorobiphenyl irradiated II III IV A Cl, Cl,, civ. Cl,, cn, ci. trace Civ, Cl,.Cl, Cl,, C1T (Fig. 1) Cl., Clr B m/e 476, Chloroterphenyls - m/e 248, 284, S09, S4Z (Fig. 2) trace 320, 3S4, 412, Civ, Cl, 446, 480, 574 (Fig. 3) Different minor peaks at different probo temperatures C and methylated , Legend: * Mony peaks due to rithor extensive. decomposH inn of sample* nr impuritios; no pattorn characteristic for chlorine 4so(opea apparent. Civ, Cl, etc. * tetra-pentachlorobiphenyl, etc. OSW 030222 STLCOPCB4014184 o IS) J o OJ o (V N) OJ Figure 2. Mass spectrum of "TLCband B" from 3,3',4,4'-tetrachlorobiphenyl exposed to sunlight. too 320 ' i o </) X. o u> o N) N) f- $ 374 -- i ...i 320 1 560 600 Figure 3. Hass spectrum of "TLC band B" from 2,2',<,4'.S.S'-hexEtrl-rr'b 1phenyl exposed :: sunlight.