Document K6DM7LLa4eNzoZ7N1RGXqKQoQ

.* ''< .* ,/v*, V -'i-.\ v v, \. J v- t ` ' \ .`t ' r- t . ' .: V;v; * r v,vjyv'3-..'.` 466 JOURNAL OF THE AOAC (Vol. 58, No. 3, 1975) Limitation on the Use of Antimony Pentachloride for Perchlorination of Polychlorinated Biphenyls WILLIAM J. TROTTER and SUSAN J. V. YOUNG Division of Chemistry and Physics, Food and Drug Administration, Washington, DC 20204 Two contaminants are present in commer cially available antimony pentachloride (SbCl5) used to perchlorinate polychlorinated biphenyls (PCBs) to decachlorobiphenyl (DCS). DCB is found in the SbCl5 perchlorination reaction blank in which no PCBs were added. Bromononachlorobiphenyl (BNCB) is found after use of SbCls to perchlorinate PCBs. Levels of DCB found in the SbCl5 reaction blanks from vari ous distributors ranged from 8 to 972 ng DCB/ ml SbCls. The relationship of the formation of BNCB to amounts of various PCB Aroclors perchlorinated is examined. Polychlorinated biphenyl (PCBs) residues are extracted, cleaned lip, and detected by methods similar to those used for organochlorine pesti cides. PCB residues are quantitatively deter mined by comparing the gas-liquid chromato graphic (GLC) response of the multicomponent residue and commercial PCBs (Aroclor) or a mixture of Aroclors producing a GLC response pattern similar to that of the residue (1). This approach is limited because the multicomponent PCB residue may not have the same propor tional composition as the Aroclor or Aroclors used as the quantitation reference. Residues can be composed of mixtures of chlorobiphenyl com ponents from more than 1 Aroclor. Metabolic and other environmental factors complicate the description of the PCB residue composition. There has been considerable work to develop methods to convert the multicomponent PCBs to a single derivative on which to base the resi due determination. Procedures have been re ported to catalytically dechlorinate PCBs with hydrogen over palladium or platinum to bi phenyl, cvclohexylbenzene, and bicyclohexyl (2, 3). A principal disadvantage w'ith that pro cedure is that the hydrocarbon product is determined with a GLC flame ionization detec tor. resulting in low sensitivity. Attempts have been made to convert PCBs to the fully chlor inated decachlorobiphenyl (DCB) (3-5). Ar mour (6) reported optimum conditions for perchlorinating PCBs with antimony pentachloride (SbCl6). The method provides a qualitative confirmatory procedure for PCB determination. The GLC electron capture detector response is enhanced because total PCBs are manifested as a single peak for DCB. In measuring the single peak for DCB the analyst is not faced with analytical judgments such as baseline correction, method of integration, or discrimination between PCBs and non-PCB components. However, it is necessary to be aware that the various Aroclors give rise to different equivalents of DCB (6) and that the nonchlorinated biphenyl (also used as ^P*fTfflgtClll(iJ"iy Jl&Mhlorinated By bb<Jl5 to mJ.U. Nonetheless, using the percniorinanon (lerrvatization can reinforce the residue value determined by measuring a multicomponent PCB residue. During attempts to apply the perchlorination derivatization in determining low residue levels of PCB and make use of the increased electron capture response to DCB, 2 contaminants were indicated wrhich led to erratic recoveries of DCB. Experimental Reagents.Mnd Apparatus - (a) Antimony pentachloride.--Hooker Chemical, Niagara Falls, NY 14302 (received in glass bottle with lead-lined cap) ; Matheson Coleman & Bell (MCB), Norwood, OH 45212 (reagent grade); B&A (Allied Chemical), Morristown, NJ 07960 (reagent grade, 09%); Research Organic-Inorganic Chemical (ROC-RIC), Belleville, NJ 07109 (99.99%); and J. T. Baker Chemical, Phillipsburg, NJ 08865 (Baker Analyzed Reagent). (b) Gas chromatograph.--Searle-Analytic (Des Plaines, IL 60088) Model 5360 with 6' X 4 mm id glass column containing 1% OV-101 on 80-100 mesh Chromosorb W (HP). Operating conditions: column flow, 60 ml nitrogen/min; column, 202C; detector, 202SC; injector, 225C; pin-cup design electron capture detector with titanium 3H foil; detector voltage (constant dc) adjusted to cause one-half full scale recorder deflection for 0.7 ng DCB when full scale deflection is 1 X 10" amp. (c) Mass spectrometer.--Varian MAT (25 Route 22, Springfield, NJ 070S1) CH5-DF mass spectrom eter (MS) coupled to Varian Aerograph 2740 gas DSW 297633 TI ch Bi tio G\ CO: M. en: in ittt op wa of bci Va the ter car ext in GI sec tiv rej per the ina fou Th to wa DC in lim stu clo: per of giv Hoc MC B&, RO< J. T STLCOPCB4067546 975) tion :vels tron vere >CB. iical, ittle Bell de); 7960 ;anic 7109 >rg, [Dos n id -100 sns: !C; sign Foil; mse ' nK P- oute omgas TROTTER & YOUNG: PERCHLORINATION OF PCBs 467 chromatograph via all-glass system using WatsonBiemann 2-stage separator. GLC operating condi tions : 6' X 4 mm id glass column containing 3% OV-1 on 80-100 mesh Chromosorb W (HP); column flow, 60 ml helium/min; column 240C. MS operating conditions: electron energy, 70 ev; emission current, 300 /ta; multiplier voltage, 2J2 kv. Results and Discussion A peak identical to that of DCB was found in the reaction blank for the Armour perchlorination procedure (6) with the described GLC operating conditions. The identification of DCB was confirmed by GLC-MS of a hexane extract of a hydrolyzed sample of SbCl5 which had not been subjected to the perchlorination procedure. Various quantities (05-2.0 ml) of SbCl5 from the 5 commercial sources were examined to de termine the presence of DCB. SbCI5 alone was carried through the perchlorination reaction (6) except that no CHC13 was present with SbCls in the reaction vessel. DCB was determined by GLC. Table 1 lists the amounts of DCB found. After perchlorinating PCBs with SbCl5, a secondary- peak with a GLC retention time rela tive to DCB of 1.31 was observed similar to that reported by Huckins et d. (7). This later eluting peak is seen in Fig. 1, the chromatogram from the 0.2 ml SbCl5 (Hooker Chemical) perchlor ination of 0.50 fig Aroclor 1221. This peak was found whe/TbBLlji Itofn eacn supplier was used. The peak was determined by GLC-MS to be due to bromononachlorobiphenyl (BNCB). BNCB was assumed to be a competing product with DCB arising from a small amount of SbCl4Br in SbCl5, so parameters relating to possible limitations of the perchlorination procedure were studied. Various quantities (0.5-10 fig) of Aroclors 1221, 1242, 1254, and 1260 in CHC13 were perchlorinated. Recoveries of DCB and estimates of the relative amounts of BNCB formed are given in Table 2. Calculation of the relative Table 1. DCB (ng/ml) formed from various amounts of SbClj SbClj, ml Supplier 0.2 1.0 2.0 Av. Hooker Chemical MCB B&A ROC-RIC J. T. Baker 37 44 47 43 35 42 38 38 960 1042 913 972 12 13 12 12 9 7 78 FIG. 1--Electron capture GLC curve from the 0.2 ml SbCI9 (Hooker Chemical) perchlorination of 0.50 /tg Aroclor 1221; 0.51 ng equivalent Aroclor 1221 injected. Peak 1 represents 0.81 ng DCB. Peak 2 represents 0.28 ng BNCB. amounts of BNCB product formed was based on comparison of the electron capture GLC peak height of BNCB with that of a DCB reference. The amount of DCB determined in the reac tion blank was directly proportional to the amount of SbCl5 used (Table 1). This indicates SbCl5 was the source of the DCB and that contamination from other possible sources dur ing the perchlorination was negligible. The pro cedure for perchlorinating PCBs specifies the use of 05 ml SbCl5. SbCls producing 8-972 ng SbCl5/ml in the reaction blank would add 0.5 65 ppb, based on a 3 g sample. DCB produced in the reaction blank was as sumed to come from PCB contamination of SbCl3. In an effort to locate the origin of this contamination, SbCls bottle closures were investi gated. GLC analysis of hexane, in which the plastic caps were soaked for 4 day's, did not reveal PCBs. Hooker Chemical, the sole do mestic source of SbCl6, supplied SbCl5 in glass bottles with lead-lined caps. This bulk supplier of SbCls indicated that the production of chlo rine in carbon anode half-cells with linseed oil or other organic binders forms certain organic compounds; however, the destructive oxidative environment in the electrolytic cells would make the production of PCB unlikely as a result of this pathway. On the other hand, antimony metal is commonly obtained as a metallurgical by-prod uct by carbon reduction of its oxide; therefore, DSW 297634 STLCOPCB4067547 468 journal op the aoac (Vol. 58, No. 3,1975) Table 2. DCB and BNCB from perchlorination of various Aroclors with 0.2 ml SbCIs0 Aroclor Amt, Mg DCB reed, % BNCB6 reed, % DCB + BNCB6 combined rec, % 1260 1254 1242 1221 1260 1254 1242 1221 1260 1254 1242 1221 10 10 10 10 4 4 4 4 0.5 0.5 0.5 0.5 86 84 88 67 81 80 78 70 89 78 72 60 0 0 4 16 0 0 8 18 2 6 10 19 86 84 92 83 81 80 86 88 91 84 82 79 * Hooker Chemical SbCI,. 6 Quantity calculated by comparison of electron cap ture GLC response to BNCB vs. response to DCB refer ence standard. it is conceivable that PCBs could be associated with the antimony metal employed in the SbCl5 process. No heat transfer systems containing PCBs are used in either the chlorine or SbCl3 production facilities, and SbCl5 does not come into contact with plastics in the manufacturing operation or in shipping containers (Hooker Chemical and Plastics Corp., 1974, private com munication). Two parameters (various quantities and vari ous Aroclors) were studied in relationship to the production of BNCB as a competing prod uct of DCB during the perchlorination of PCBs. BNCB was calculated by comparison of the elec tron capture GLC response to BNCB vs. the response to DCB. Several factors are considered: (1) In this reaction bromination is kineticallv favored over chlorination. With perchlorination of lower amounts of PCBs the relative yield of BNCB to DCB is greater because the brominating agent is the limiting quantity in contam inated SbCl5. (2) Bromination occurs to a larger degree for a given quantity of the less chlori nated PCBs such as Aroclors 1221 and 1242. rather than for 1254 and 1260. This likely is due to a greater number of reactive sites and less steric hindrance. (3) In the range of PCBs perchlorinated (0.5-10 fig) in the above study, it is likely that with lower amounts of PCBs and/ or less chlorinated Aroclors the decrease in DCB recovery is principally due to the increase of BNCB formed. One of the major advantages of perchlorina tion in determining minute quantities of PCBs is the inherent increase in effective GLC detec tor response. Contaminated SbCl5, as described here, would preclude its use in many of these cases. References (1) Official Methods o] Analysis (1975) 12th Ed., AOAC, Washington, DC, secs. 29.001-29.007 (2) Asai, R., Gunther, R., Westlake, W., & Iwata, Y. (1971) J. Agr. Food Chem. 19, 396-398 (3) Berg, O. W., Diosady, P. L., & Rees, G. A. V. (1972) Bull. Environ. Contam. Toxicol. 7, 338-347 (4) Hutzinger, O. W., Safe, S., & Zitko, V. (1972) Int. J. Environ. Anal. Chem. 2, 95-106 (5) Hutzinger, O. W., Jamieson, D., Safe, S., & Zitko, V. (1973) JAOAC 56, 982-986 (6) Armour, J. A. (1973) JAOAC 56, 987-993 (7) Huckins,'J. N., Swanson, J. E., & Stalling, D. L. (1974) JAOAC 57, 416-417 Received August 21, 1074. This papier was presented at the 88th Annual Meeting of the AOAC, Oct. 14--17,. 1974, at Washington, DC. . . COPPOLA h Fluoroi ELIA D. < The Conne An indi) mining sod sented. The in a diazi excess of s acts selecti sulfanilic a excess amii by differen is directly i of the sam and solubh eliminated in the fluoi 495 nm flu ment at lo' dium nitrit an average of 5.28% The use t additives in in the Unit, lion pounds salami, fran are product there has b tential heal additives in nitrite, reac in the body, (1-3). The limited by f 200 ppm soi There art nitrite in m method (4) colorimetric is.diazotized to form a ct method was by Nicholas factory. Ho\ expressed re. thylamine, w the non-carc 207635 OSNN STLCOPCB4067548