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pergamonP l I : S 0 0 4 5 - 6 5 3 5 ( 9 6 ) 0 0 2 1 4 - 7

Chemosphere, Vol . 33 , No . 4 , pp . 603 - 623 , 1996C o p y r i g h t 1 9 9 6 E l s e v i er S c i e n c e L t dPr in t ed in G r ea t Br i t a in . Al l f i gh t s r ese rved0 0 4 5 - 6 5 3 5 / 9 6 $ 1 5 . 0 0 + 0 . 0 0

C O M P R E H E N S I V E , Q U A N T I T A T IV E , C O N G E N E R - S P E C I F IC A N A L Y S E SO F E I G H T A R O C L O R S A N D C O M P L E T E P C B C O N G E N E R A S S IG N M E N T S

O N D B - I C A P I L L A R Y G C C O L U M N S

George M . Frame*, R ob er t E . Wagner *l , James C. Carnahan, John F. Bro wn , Jr. , Ralp h J. M ay,Lyn n A. Smullen, and Do nna L . Bedard

General E lectric Co rporate Research and Development, P .O. B ox 8Schenectady, /flY, 12301-0008, USA

( Rece ived in Ger many 15 Apr i l 1996 ; accep ted 14 May 1996)

A B S T R A C TW e have determined com plete polycldorinated biphenyl (PC B) congener assignments end we ight percent

dis tr ibu tions for al l major ( > 0 .5 wt % ) FCB components o f Aro clors 122 1, 1232, 1242, 1016, 1248 , 1254,1260, 1262 that are resolved b y DB-1 (polydimethylsiloxane) capillary C,-C columns. A roc lor com pon ents presentbetween 0 .05 and 0 .5 w t % we re also identi fied bu t not quant if ied . Quantitadon wa s don e us ing a combination o fGC -EL CD (Hall electrolyt ic conductivity detector) and GC -MS m easurements . All 209 PC B congeners havebeen ass igned to the 124 peaks that can be resolved on DB -I columns . The data supp or t use of these eightAroclors individually or in customized standards for calibrating the comprehensive, quantitative, congener-specific PC B analyses that are necessary for accurate quantitation o f the comp lex and ofte n radically alteredmixtures o f PC Bs typically found in the environment . Copyr ight 1996 Elsevier Science Ltd

I N T R O D U C T I O NFro m 1929 to 1979, polycldorinated biphenyls (PCBs) w ere widely used as dielectric fluids in capacitors

and transformers, and also as hydraulic fluids, solvents, and plastieizers. FC Bs are considered potentially toxic,hen ce the PC B s that s till persist in soils , sediments, and biota are a m ajor environmental concern.

Comm ercial PC Bs w ere m anufactured by catalyt ic chlor inat ion o f b iphenyl to prod uce co mp lex mix tures,each containing 60 to 90 different molecular species (congeners) and a specified we ight percent o f chlorine.

Current address: No rthe ast Analytical, Inc. , 301 N ott Street, Schenectady, N Y , 12305

6 0 3

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604Congener distributions in environmental samples resemble those of the parent commercial mixtures (Aroclors inthe USA and Great Britain, Clophens in Germany, or Kanechlors in Japan), but are often modified due toevaporation, water extraction, microbial oxidation or dechlorination (1 ,2 ,3 ) , or photochemical dechlorination (4).

There are 209 distinct congener structures possible, of which about 140 to 150 have been detected atsignificant levels in commercial PCBs (5). Thus a comprehensive analysis of the congener distributions in anenvironmental or research sample presents a daunting analytical problem. Regulatory agencies in Europe havesimplified the problem somewhat by specifying a list of seven "indicator" congeners (6) or 36 "priority"congeners (7) targeted for individual quantitation. The US EPA specifies that PCB quantitation must be done bycomparison of total area or total height of sample peaks to those of one or more reference Arociors, dependingon the chromatographic pattern of the sample (8). However, many research studies require complete, quantita-tive measurements of all the PCBs that can be resolved and detected. Analytical methods that attempt to achievecomplete, quantitative, congener-specific measurement of PCBs will be referred to as c o m p r e h e n s i v e ,quanatat ive, congener-_speci f ic (COCS) PCB analyses.

The use of well-characterized i n d i v i d u a l Aroclor standards for calibrating CQCS PCB analyses hasseveral advantages. (1) Aroclor standards are easier to use and are far less expensive than standards based oncomplete sets of individual congeners. (2) Their congener distributions are similar to those found in theenvironment, hence they are well-suited to calibrations based on diluting or concentrating the sample extract tomatch a single concentration of the standard (9). (3) Individual Aroclor standards can be combined in variousproportions to match the chromatographic pattern in a sample, and can be supplemented with individualcongeners to make customized standards. This permits accurate quantitation of the complex mixtures of PCBstypically found in the environment, including those altered by degradation, dechlorination, evaporation, andwater extraction (1 0 ) .

To employ Aroclors as standards for CQCS analyses, the analyst requires the individual weight percentvalues of total PCBs in each peak on the particular HP,GC column, and for GC-MS methods the proportions ofdifferent h o m o l o g s (congeners of a particular chlorine number) within a peak. Accurate quantitation generallyrequires assignment of all likely congeners to each resolvable peak of each Aroclor on a particular HR.GC columnbecause the chlorine substitution pattern affects the molar response of the detectors most often used for PCBanalysis, i.e. the electron capture detector (ECD), and mass spectrometer (MS) (11, 12).

Bush e t a l . ( 1 3 , 1 4 ) and Eganhouse e t a l . ( 1 5 ) have described CQCS PCB analyses calibrated againsts i n g l e s p e c i f i c m i x t u r e s of three or four Arociors employed as secondary standards. Such methods employtables of the amounts of PCB in each peak of the m i x e d Aroclor standard o n a p a rt i c ul a r H R G C c o lu m n , asdetermined by a primary analysis of the mixed Aroclor standard, together with an assignment of congeners to thepeaks of the system. Unfortunately, many of the 209 PCB congeners were not available as reference standardswhen these studies were done, and consequently there were errors in the congener assignments made by theseinvestigators. There is also some concern about the quantitation because both groups relied on detectors thatmay be sensitive to the chlorine substitution patterns of individual congeners. Bush e t a l . (13, 14) used MShomolog responses, and Eganhouse e t a l. (1 5 ) used a combination of FID and MS homolog responses tocalibrate their secondary standard mixture of Aroclors. There is general agreement that MS detectors aresensitive to chlorine substitution patterns (1 2 ) , but there is some disagreement about whether this is also true forFID de~eetors. Albro and Fishbein (11 , 16 ) reported that the relative molar response of the FrD detector to PCB

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605c onge ne r s can va ry s igni f icant lywi th the chlor ine subst itu tion pa t te rn . Ho wev er , in mo re recent wor k Krupc ik e la l . ( 1 7 ) r e por t e d t ha t t he m ola r r e sponse f a c to r s o f t he F I D de t e c to r t o a l l P CB c onge ne r s a r e c ons t a n t t o w i th inab ou t .4- 10% .

K r u p c i k e t a l. ( 1 7 ) r e c om m e nde d a p r oc e du r e f o r c om b in ing G C- FI D a nd G C- MS m e a su r e m e n t s o fA r oc lo r s o r C lophe ns t o su ppor t t he i r u se a s s e c onda r y s ta nda r ds fo r CQC S P CB a na lyse s o n spe c i fi c c a p i ll a ryG C c o lu m ns. T he se a u thor s su b se q u e n t ly p r opose d the u se o f G C- FI D da t a t o c a l i br a t e pe a k r e sponse s o f m o r ese l e ct i ve de t e c to r s f o r pa r t i c u l a r A r oc lo r s o r C lophe ns on a ny c a p i ll a r y c o lu m n ( 1 8 ) . A s a n i l lus tra t ion, the yshowe d h ow th i s p r oc e d u r e c ou ld b e u se d t o p r odu c e r e l a ti ve r e sponse f a c to r s ( R R Fs ) f o r G C- ECD ,G C - M S - S I M a nd G C - MS - T I C ( t o t a l i on c u r r e n t f r om sc anned a c qu is it ion ) f o r i nd iv idu a l pe a k s o f A r oc lo r s 1242a nd 1260 o n a po lyd im e thy l s il ox a ne c a p i l la r y c o lu m n ve r y s im il ar t o t he D B- 1 pha se a nd r e por t e d w e igh tpe r c e n t a ge s f o r m a jo r pe a k s o f the i r s a m ple s o f A r oc lo r s 1242 a nd 1260 ( 1 7 ) . Howe ve r , t he r e a r e m a jo rd i sc r e pa nc ie s b e twe e n t he c onge ne r s t he y r e por t e d a s m a jo r c ons ti t ue n t s o f A r o c lo r 1242 a nd 1260 pe a k s a ndthose we r e por t i n t h i s pa pe r.

A n o the r A r oc lo r - c a l i b r a t e d CQC S P CB a nalys is e m p loys Mu l l i n 's " G r e e n Ba y Ca l ib r a ti on Mix tu r e " ( 1 9 )whic h i s c om pose d o f A r oc lo r s 1232 :1248:1262 i n t he r a t i o s 28 :18 ; 18. T he se A r oc lo r s we r e ob t a ine d fr om aUS EP A r e pos i t o r y . Mu l l i n a s s igne d 126 A r o c lo r c onge ne r s t o 103 pe a k s on a DB- 5 c o lu m n a f t e r a na lyz ing t hemix ture on severa l d i f fe rent columns ag a ins t individua l cong ener s tandards and us ing m ass spec t ra l de tec t io n insom e cases . Al thoug h the metho d has n ot been form al ly publi shed, M ul l in mak es ava i lab le a new mix ture us ing ane w sou r c e o f EP A A r oc lo r s , toge th e r w i th u pda t e d e lu t ion o r de r a nd pe a k q u a n t i ta t i on ta b l es . T he c a l ib r a ti onhas bee n em ploy ed in severa l studies , (e .g . 20 , 21) , pa r t ic u l a rl y i n t he G r e a t L a k e s ( US A ) r e g iona l su r ve ys.

De spi te i t s usefu lness , th e Gree n Bay C al ib ra t ion M ethod has severa l s igni ficant sh or tcoming s . Fi r s t , thes t a nda r d sk ips fr om A r o c lo r 1 248 t o A r oc lo r 1262 a nd t he r e b y e x c lu de s m a ny pe n t a c h lo rob iphe ny l s t ha t r e a c hs ign if ic an t p r o por t i ons on ly in A r o c lo r 12 54 . T hu s t he m e thod m a y no t b e we l l - su i t e d f o r q u a n t i ta t i on o fsa m ple s t ha t c on t a in s i gn if ic a nt p r o por t i ons o f A r oc lo r 1254 o r o f pe n t a c h lo r ob iphe ny l s f o r m e d b yde c h lo r ina t i on o f m or e c h lo r ina te d c onge ne r s . S e c ond , s i nc e t h is m e thod i s b a se d on a f i x e d s t a nda rd , i t doe snot a f ford the f lex ib i li ty tha t can be achieved f rom m ethods based on wel l -cha rac te r ized i n c ~ v i d u a l A r o c l o rs tandards .

P r e v iou s ly , on ly two g r ou ps ( 2 2 , 2 3 ) ha ve a t t e m pte d c om ple t e CQC S a na lyse s c a l i br a t e d a ga ins t p r im a r ys tandards o f a ll 209 congen ers , mos t o f which w ere spec i fica l ly synthes ized by the researchers for tha t pu rpose .Mul l in e t a l. ( 2 2 ) u se d a 100m S E- 54 c o lu m n wi th a 2 hou r r u n t im e a nd r e por t e d r e so lu t ion o f 18 7 o f t he 209congeners . Schulz e t a l. ( 2 3 ) e m ploye d he a r t - c u t t i ng 2 - d im e ns iona l HR G C to de t e r m ine c om ple t e c onge ne rd i s t ri b u t ions o f f ou r A r o c lo r a nd f ou r C lophe n m ix tu re s. Bo th o f the se p r oc e d u r e s a r e t oo s l ow a nd d if fi cu lt f o rr ou t i ne CQC S a na lyse s o f l a r ge nu m b e r s o f sa m ple s, a nd shor t e r c o lu m ns a nd r u n t im e s do no t a c h i e ve the s a m eresolu t ion (6) . Un for tuna te ly , there i s s ti ll no s ingle HR GC sys tem tha t wi l l r esolv e a l l 209 PC B cong eners ore ve n a l l t hose t ha t oc c u r i n A r oc lo r s .

T o c a l i b r a te CQ CS P CB a na lyses i n ou r l ab s , we m e a su re d t he t o t a l P CB c on t e n t o f e a c h pe a k i n s a m ple so f e igh t d i f f er e n t A r oc lo r s b y c om b in ing da t a on t he c h lo r ine c on t e n t m e a su r e d b y a n e l e c t ro ly t i c c ondu c t i v i tyde t e c to r ( ELCD , a l so k nown a s a Ha l l de t e c to r ) w i th da t a on t he hom o log c om pos i t i on de t e rm ine d b y G C - MS .T he ELCD a f f o r de d a d i s t i nc t a dva n t a ge ove r o the r m e thods o f q u a n t i t a t i on b e c a u se t he r e sponse o f t h i sde t e c to r i s d i r e c tl y p r opor t i ona l t o t h e n u m b e r o f c h lo r i ne s i r r espe c t i ve o f t he po s i t i on o f t he c h lo r ine s ( 1 2 ) .

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60 6W e b b a n d M c C a l l ( 2 4 ) u se d a c om b ina t i on o f ELC D a nd MS da t a fo r q u an ti fy ing t he P CB c om po s i t ion o fA r od or s b y pa c k e d c o lu m n G C b e c a u se t h i s a ppr oa c h pe r m i t s a c c u r a te q u a n t it a t ion o f t he P C Bs i n e a c h A r oc lo rpe a k e ve n w he n t he P C B c onge ne r c om pos i t i on is no t k nown. Us ing DB - I ( po lyd im e thy i s il ox a ne ) c ap il la ryc o lu m ns we w e r e a b l e t o r e so lve 118 P CB pe a k s t o wh ic h we a s s igne d 184 o f t he 209 c onge ne r s . Ove r t he pa s t9 years , our con gen er ass ignments and w eight percent d is t r ibu tions for these Aro c lor s prov ided the founda t ionfor ana lyt ica l me thods implemented by a n umber o f indus t r ia l r esearch, con t rac t and academ ic labora tor ies tosu ppor t e nv i r onm e n ta l a nd i n v i t ro microbia l PC B degrad a t ion and dechlor ina t ion s tudies ( 2 5 - 3 4 ) . A s m or e pu r econg ener re fe rence s tandards became ava i lab le , and th e chro matog raphic condi t ions of the ana lyt ica l methodwe r e a l t e re d a nd op t im ize d , we r e v i se d a nd e x t e nde d som e o f t he i n it ia l c onge ne r a s s ignm e n t s a nd m a de se ve ra la dd i t i ons a nd de l e t i ons in t he pe a k nu m b er ing syst em . T he pu r pose o f th i s pa pe r i s t o r e por t t he D B- 1 pe a kassignments for a l l 209 congeners , to ind ica te which o f the cong eners a re s igni ficant c om pon ents o f Aroc lor s ,and to pres ent tab les o f cong ener ass ignments and weig ht percent d is t ribu t ions for a l l pea ks resolved on DB -1c o lu m ns f o r e a c h o f t he e igh t A r oc lo r s u se d a s s e c onda r y c a ii b r at i on s t a nda rds f o r ou r C QC S P CB a nalyses .

M A T E R I A L S A N D M E T H O D SR e a ge n t s . A r oc lo r s a nd P CB c onge ne r s we r e d i s so lve d i n high pu r i t y he x a ne o r i sooe t a ne . T he e igh t

A r oc lo r s c ha r a c t e ri ze d in t h i s s t u dy we r e ob t a ine d f r om the m a nuf ac tu re r ( Mo nsa n to Cor p . , S t . Lou i s , MO ,US A) d ur ing the t ime whe n A roc lo rs we re s t i ll wide ly used. T hese spec if ic A roc lo r samples have subsequent lybeen used as secondary s tandards in a l l of our s tudies . In i t ia l ca l ib ra t ion s tandard PCB congeners ,chloronaphtha lene in te rna l s tandards , and individua l PCB congener s tandards were ob ta ined e i ther f rom Ul t raS c ie n ti fi c ( N or th K ings ton R / , US A ) , o r A c c u S ta nda r d Inc . , (N e w Ha ve n C T , U S A ) . A c om ple t e s e t o f 209P CB c onge ne r s u se d f o r t he f ina l c om pr e he ns ive DB- 1 c o lu m n pe a k a s s ignm e n t s wa s ob t a ine d fr omA c c u S ta nda r d I nc.

S t a n da r d S o lu t i ons . A c a l i b ra t ion s t a nda r d o f c onge ne r s r e p r e se n t i ng e a c h hom o log c la s s wa s p r e pa r e db y we igh ing ou t - 5 m g e a c h o f P CB s 3 , 5 , 18 , 49 , 101 , 153 , 18 5 , 202 , 206 a nd 209 a nd d i s so lv ing t he m inhe x a ne a t a f ina l vo lu m e o f 25 m l . T h is s t oc k w a s d i l ut e d to p r odu c e t h r e e c a l i b r a ti on l e ve ls o f e a c h c onge ne r a t~ 10 , ~ 50 , a nd - 1 0 0 pg /m l . A c a l i b r a ti on c he c k s t anda r d re p r e se n ti ng a l l hom olog c l a s se s e x c e p tnonach lorob ipheny is w as prep ared in the same way us ing PC Bs 1 , 12, 30, 52, 101 , 156, 185, 201 and 209 andwas di lu ted to ~5 0 pg/ml . Ea ch ca l ib ra t ion solu t ion conta ined 1 ,2-dichloronaphtha lene , 1 ,2 ,3 ,4- te t rachloro-naphtha lene , and oc tachloron aphtha len e as in te rna l s tandards ( I . S . ) a t individua l con cent ra t ions o f 50 I~g/ml.

Conc e n t r a t e d so lu t i ons ( ~ 1000 pg /m l ) o f A r oc lo r s 1221 , 1232 , 1016 , 1242 , 1248, 1254, 1260 a nd 1262we re prepa red in hexane . 1 ,2-Dichloronaphthaiene was add ed to each Aro c lor solu t ion a t a f ina l concent ra t ionof 50 pg /m L Ei the r one o r b o th o f t he o the r two c h lo r ona ph tha le nes we r e a l so a dde d a t t he s a m e c onc e n t r a ti onwhe ne v e r the y d id no t c oe lu t e w i th a P CB pe a k i n t he A soc lo r .

G C - E L C D A n a l y s e s . C a p i ll a ry G C w i th d e t ec t io n b y t h e E L C D w a s c a rr ie d o u t o n a V a r ia n 4 6 0 0 g a sc hr om a tog r a ph e q u ippe d wi th a T r a c or M ode l 700A E L C D S p l i tl e s s i n j e c ti ons ( 1 .0 p l ) we r e m a de us ing aVar ian Mo del 80 00 au tosam pler and a 1070 spl i t / spl i t less in jec tor wi th a spl i t less t ime o f 0 .9 min a t 300C. Thecolumn wa s a DB -1 (bonded , c ross- l inked, 100% polydimethyls iloxane) capi l la ry colum n ( J&W , 30m x 0 .25rami .d . x l .0 pm f ilm thickness) . The th ick f ilm was necessary to pro vide adequa te s amp le capac i ty for the high

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607concentration (1000 p.g/mi) Aroclor injections. The column temperature was held at 40C for 2 rain.,programmed to 80C at 10C/rain and then to 225C at 6C/rain and held for 10 min. The carder gas was heliumat a flow rate of 1.8 ml/min. The ELCD detector base was maintained at 300C and the reactor was providedwith hydrogen gas (serving also as column makeup gas) at a flow rate of 50.0 ml/min and n-propanol solventflow of approximately 1.0 ml/min (corresponding to a setting of 6.8 on the detector). The ELCD reactor wasoperated at 920C, and the column efiluent was diverted for the first 0.35 rain atter injection to avoidcontamination from the injection solvent. Peak areas were measured using a Vadan 402 workstation.

1,2-Dichloronaphthalene was chosen as the I.S. for the Aroclor quantitation because it did not coelutewith any Aroclor peaks. The remaining I.S. compounds were introduced into Aroclor solutions when they didnot coelute with Aroclor peaks and served as a check on the stability of the ELCD detector response, but theywere not used in the quantitative calculations.

GC-MS Analyses. The same DB-I column was transferred to a GC-MS system in order to determinethe PCB homolog composition of each resolvable peak on the GC-ELCD system described above. Aroclorsolutions (5000 I~g/ml) were analyzed on a Varian 1440 GC directly interfaced to a VG ZAB 2F massspectrometer operated in the low resolution mode. Depending on the particular Aroclor, a variety of differentcolumn flow and temperature programs were employed with the G-C-MS system to produce peak distributionsand resolutions matching those recorded during the GC-ELCD analyses. Electron impact (70eV) mass spectrawere acquired by continuouslyscanning the range of 154 to 500 atomic mass units.

The PCB homolog composition of each resolvable peak in each Aroclor was determined from the massspectra. Chromatographic peak areas from the mass chromatograms of each chlorine isotope mass peak in thehomolog molecular ion clusters were summed to yield total cluster signal values for that homolog. The weightfraction of each homolog in the peak was assumed to be the ratio of its molecular ion cluster area to the sum ofthe areas of the pair. In most instances the relative proportions of coeluting homologs in any GC peak could beaccurately determined when they differed by a single chlorine, which was generally the case. However, therewere two instances, peaks 60 and 96, where coeluting homologs differed by two chlorines. The morechlorinated homolog was predominant in each of these peaks, hence the fragment produced by the loss of twochlorines precluded measurement o f the less chlorinated homolog.

GC-ECD Analyses. Routine CQCS PCB analyses were performed using thinner film DB-1 columnswith more sensitive detectors, especially the ECD. We determined how closely the distribution and resolution ofpeaks on the DB-1 thick film column systems described above matched such a G-C-ECD system. We used a J&WDB-I column (30 m x 0.25 mm i.d. x 0.25 ~m film) and a Varian ECD installed in the GC system previouslyused for GC-ELCD determinations. The temperature and flow parameters were the same except that the columnlinear flow rate for the helium carder gas was 30 cm/sec. Nitrogen at 25 ml/min was employed as the makeupgas. The resolution of congeners was identical to that on the GC-ELCD and GC-MS systems in all but 4 cases.These exceptions were taken into account during the calculation of the final Aroclor weight percent distributions,which are presented for the thin film column/ECD peak distribution.

BiphenylAnalysis. The biphenyl content of our samples of Aroclors 1221 and 1232 was determined byanalyzing hexane solutions of these Arociors (~100 ~g/ml) in triplicate (RSD = 5% and 3% respectively) againsta 5 point standard curve using a DB-I capillary column with flame ionization detection.

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608Elemental (C, H, CI) Analysis. The eight Aroclor samples were sent to Galbraith Laboratories

(Knoxville, TN, USA) for analysis of carbon and hydrogen content by automated elemental analyzer and ofchlorine content by Sch6niger flask oxygen combustion followed by potentiometric titration.

RESULTSC o n f i r m a t i o n o f ELCD Linear Response to Chlorines. The calibration standard and calibration check

standard were each analyzed several times on the GC-ELCD system to verify that the ELCD response wasdirectly proportional to the number of chlorines and not sensitive to chlorine position. The results confirmed thisand verified that congeners of a given chlorination level yielded the same responses relative to an individual I.S.The ratios of all three internal standards relative to each other were monitored both in the calibration standardsand in the Arociors to ensure that the response of the ELCD did not change during analysis. These ratiosremained constant, demonstrating that the ELCD response was stable.

Determination o f H o m o l n g C o m p o s i t io n o f A r o c l o r s . The homolog composition (i.e. chlorinationlevel) of each peak in our samples of each of the eight Aroclors was determined from GC-MS data. In caseswhere the GC-MS analysis revealed coelution of more than one homolog in a peak, the approximate weightfraction of each was calculated as described above.

Calculation of PCB Concentrations in Aroclors. Each of the three concentrations of the calibrationmix was analyzed six times on the GC-ELCD system using 1,2-dichloronaphthalene as an internal standard tonormalize the data and compensate for any shit, s in the ELCD response. The mean ratios (PCB peak area/I.S.peak area) were calculated for each calibration level and used to generate 3-point linear calibration curves foreach of the ten chlorination levels. The slopes and intercepts were calculated for each chlorination level.

Each of the Aroclors was then analyzed six times. Because the ELCD response for each chlorinationlevel is constant, the concentration of the PCB was calculated directly using the formula:

PCB Cone. (~g/ml) = S x (Peak Area/I .S. Area) + Iwhere S is the slope (for the chlorination level) and I is the intercept. For peaks with mixed chlorination levels,GC-MS analysis was used to determine approximate weight fractions of pairs of coeluting homologs, and thesewere introduced into the formulas:

PCB Cone.L (p.g/ml)= SL x (Peak Area x FL/I.S" Area)+ IL andPCB Cone.H (~g/ml) = SH (Peak Area FH/I.S. Area) + I H

where F is the approximate weight fraction determined by GC-MS, and L and H designate the lower and higherhomologs, respectively. The combined sum of the PCB concentrations for the higher and lower homologsconstitute the "total" Izg/ml concentration for each mixed peak.

Calculation of Weight Percent PCB Distributions for Peaks Quantifi able by ELCD. The PCBconcentrations for each peak were summed to give the total PCB concentration for each replicate run. Theweight percentages for each homolog in each peak were calculated for each replicate run using the formula:

Weight A PCB = [ Cone. PCB (~g/ml)/Total Cone. (~g/mi) ] x 100

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609The final weight percent values for each peak (including different homolog chlorination levels within

peaks) were generated by taking the mean of the six replicate values. The percent relative standard deviations ofthese means for individual peaks in the eight Aroclors averaged - 3% with a maximum range of 0.42% to 7.2%.

Iden tifi cation of Min or Aroclor Peaks. We were able to detect a number of minor Aroclor peaks withGC-ECD or GS-MS-SIM that were not quantifiable by the GC-ELCD used in this study. We used semi-quantitative analyses of each Aroclor on several different systems to identify congeners in DB-1 column peaksthat were present within the concentration range of 0.05 to 0.50 weight percent. Peaks in this range detected ona DB-1 column by GC-ECD were quantified using tables of response factors adapted from Mullin e t a l . ( 2 2 ) andcorrected for our ECD. The homolog composition of these peaks was determined by GC-MS-SIM on the samecolumn. Each Aroclor was also analyzed against individual standards of all 209 congeners on both a 30 mDB-XLB column (J&W Scientific) using MS-SIM detection and a 30 m SPB-Octyl column (Supelco, Inc.Bellefonte, PA, USA) using ECD detection (G. Frame, unpublished data). Ratios of peak heights to theindividual standards provided a semi-quantitative estimate of the amounts present. These additional systems alsoenabled resolution and quantitation of congeners that coelute on DB-1 columns.

Total PCB C o n c e n t r a t i o n a n d Weight Percentage of Chlorine for Eight Aroclors. Table 1 gives theactual concentrations of each of the Aroclor solutions and compares them to the range of values calculated fromthe six replicate GC-ELCD analyses. Aroclors 1221 and 1232 contain substantial amounts ofbiphenyl that werenot detected by the ELCD detector. We determined by DB-1 capillary GC-FID that biphenyl constitutes 11.7weight percent of Aroclor 1221 and 6.2 weight percent of Aroclor 1232 and included these values in the totalsreported in Table 1. The actual PCB concentration of several Aroclors fell outside the range calculated based onour data. However, in those instances the actual concentrations differed from the calculated range by only 2 to8% except that of Aroclor 1242 which differed by 12%. The chlorine percentages calculated from the ELCDanalysis were close to the values obtained by elemental analysis, and to the nominal percentages specified foreach Aroclor.

Table 1. Total PCB Concentration and Weight Percentages of Chlorine for Eight Aroclors:Direct Measurements Vs Calculations Based on GC-ELCD / GC-MS DataAroclor Actual Cone. Calcul~ed Cone. Elemental Analvsis Weight Percents ELCD Data

(~g/ml) Range (~g/ml) C H C1 Cl Wt %1221 I018 92 8- I000 73.59 4.50 21.96 23.81232 1036 1010- 1050 64.76 3.59 31.82 34.01242 1024 l l6 0 - 1220 54.42 2.55 43.22 43.71016 1 0 4 1 1020-1060 55.95 2.72 41.31 41.I1248 1033 98 0- 1070 49.67 2.08 48.12 48.11254 1048 1130 - 1180 43.88 1.50 54.77 54.61260 1097 1140 -1290 38.36 0.94 60.52 60.51262 994 1080 - 1100 37.26 0.82 62.01 61.8

C o n g e n e r P e a k E l u t io n A s s ig n m e n t s f o r D B -1 C o l u m n s . We initially determined the peak elutionpositions for 70 PCB congeners by Co-injecting pure congener standards with Aroclors. Estimates of probableDB-1 relative retention times were made for congeners without reference standards based on published relative

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6 1 0re tent ion t imes o f 209 con geners on a s l ight ly d i ffe rent column phase (SE -54) (22) . Thus , ass ignm ents weremad e for 184 of the 209 co ngeners to 118 dis tinc t, potent ia l ly resolvab le DB -1 peak s (26) . The se assignmentsinc lu de d som e c onge n e r s wh ic h a r e no t ob se r ve d i n a ny o f t he c om m e r c ia l A r o c lo r m ix tu r e s Ou r pe a ka s s ignm e n t s we r e r e v i se d and e x t e nde d i n 1992 (10) and f ina l ly comple ted and reconf i rmed in 1994 us ing thecom ple te se t o f 209 congeners. The co mp le te cong ener peak ass ignments for DB-1 columns a re l i s ted in Table 2 .

D B - I C h r o m a t o g r a m s f o r I n d i v i d u a l A r o c lo r s , F i gu r es I A an d B s h o w th e E C D c h r o m a to g r am s f o reach o f the e ight A roc lo r s charac te r ized in th is s tudy and ident if ies a l l majo r peaks an d m ost mino r peaks .A r oc lo r s 1221 , 1232 , 1016 , a nd 1242 a r e a l l p lo t t e d on t he s a m e t im e sc al e t o pe r m i t d i r e ct c om pa r i sons o f thepe a k d i s t ri b u ti ons . A r oc lo r s 1248 and 1254 a r e p lo t t e d on a s e c ond tim e sc a le a nd A r oc lo r s 1260 a nd 1262 on athi rd time scale . Ea ch ch romato gram is p lot ted to sh ow the highes t peak on sca le.

Congener Assignments for I n d iv idu a l A r o c lo r s . P o t e n t ia l c onge ne r s c on t r ib u t i ng t o i ndividu a lA r o c lo r pe a k s we r e i den ti fi ed b y e lu t ion pos i t i on on D B- I c o lu m ns. T he p r e se nc e o r a b se nc e o f c oe lu t ingcong eners tha t d i f fe r in chlor ine number was de te rmined by GC-M S. In ins tances wh ere individua l i somerscoe lu te on the DB -1 column, tho se congene rs tha t s ignif icantly cont r ibu te to a g iven peak in each A roc io r wereinit ia lly ident i f ied on th e bas is o f observed s ingle phenyl r ing subs t i tu tion probabi l i t ies . Fo r exam ple , in pe ak 48 ,c onge ne r 95 ( 236- 25- CB ) wa s l i s te d a s the m a jo r pe nt ac h io rob ipheny l c om p one n t b e c a u se t he 236- a nd 25-c h lo r ophe ny l su b s t it u t ions a re ve ry c om m on in t he A r oc lo r s . Conge n e r 102 ( 245- 26- CB ) wa s t hou gh t t o b epr e se n t, b u t l e s s a b unda n t b e c a u se t he 26 - su b s t it u t ion i s r a r e in A r oc lo r s, c onge n e r 98 ( 246- 23- CB) wa s no tt hou gh t t o b e p r e se n t b e c a u se t he 246- su b s t it u ti on is e x t re m e ly unc om m on in A r oc lo r s , a nd c onge ne r s 8 8 a nd93 ( 2346- 2 - CB a nd 2356- 2 - CB) w e r e no t t hou gh t t o b e p r e se n t b e c a u se o f t he h igh ly u nb a l a nce d c h lo rinedis t r ibu t ion on the r ings o f these congeners . The individua l con geners ass igned as s igni ficant cons t i tuents o f eachindividua l Aroc lor were recent ly ver i f ied by chromatographing the individua l Aroc lor s aga ins t individua ls t a nda r ds o f a l l 209 c onge ne r s on two a dd i t i ona l G C c o lu m n pha se s ( DB- XLB a nd S P B- Oc ty l ) ( G . F r a m e ,unpublished data) .

T a b l e 2 g ive s t he c onge ne r a nd we igh t p e r c e n t d i s tr i b u ti ons f o r e a c h o f t he e igh t A r oc lo r s we a nalyze d.T he f i r s t c o lu m n g ive s t he pe a k nu m be rs on t h e D B- I G C c o lu m n in o r de r o f i nc r e a s ing e lu t i on t im e . T he p e a knumbers a re based on the in i t ia l 118 peak ass ignments . Changes in the GC column f low and tempera turep r ogr a m s t ha t w e now u se ha ve im pr ove d t he r e so lu ti on o f c e rt a in c lose ly e lu ti ng pa ir s . I n t e rpo l a t i ons o faddi t iona l peak numbers a re indica ted by mul t ip le dec imal va lues of the or ig ina l numbers so tha t peaks can beso r t e d nu m e r ic a l ly b y c om p u te r p rogr a m s . P e a k s 18 (c onge ne r 23 ), 8 6 ( c onge ne r 166) a nd 97 ( c onge ne r 157) o fthe or ig ina l sys tem are no lo nger found to be resolvab le , and a re there fore om i t ted .

W e ha ve l i s te d t he I UP A C nu m b e r o f e a c h c onge ner . S ix o f t he I UP A C nu m b e r s d i f f e r f r om the o r i gina lBal l schm ite r and Ze l l numbers , (BZ#) , (35): IU PA C #s 107 , 108 , 109 , 199 , 200, 201 cor resp ond to BZ #s 108 ,109, 1 07, 201, 199, and 200, r esp ec t ive ly (36). Con geners de te rmined to be presen t in any of the A roc lor s a t> 0 .05 wt % ( se e b e low) a r e i nd i c a te d in a l a r ge r b o ld f a c e fon t whe r e a s t hose no t p r e se n t i n the A r oc lo r s a reindica ted by a smal le r i ta l ic ized font .

W e hav e ident i f ied each cong ener by i t s individua l phenyl r ing chlor ine subs t i tu t ion pa t te rns according tothe con ven tion: 234 -245 = 2,2',3,4,4' ,5 ' -hexachlorobiphenyl. Th is perm its eas y visua lization o f the chlor inationpa t te rn on each r ing an d ass i s t s in te rpre ta t ion of how th e ov era l l chlor ine subs t i tu tion pa t te rn o n each r ing a ffectse lu t ion pos i t ion.

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F i g u r e I A . D I b l E C D C h r o m a t o g r a m s f o r A r o e lo r l 1221, 1232 , 1016, a n d 1242. Ea c h A r oc lo r wa sd i s so lve d i n i sooc t a ne a t a c onc e n t r a ti on o f 2 pg /m l a nd a n a lyze d on a H e wle t t P a c k a r d 58 90 G C u s ingc hr om a togr a ph y c ond i t ions s im i la r t o t hose de sc r ib e d in t he t e x t . A r oc lo r pe a k s ha v e b e e n i nd i c a t e d b y DB- 1pe a k n u m b e r ( s e e T a b l e 2 ) o r b y t i c k m a rk s. S om e o f t he m inor pe a k s w e r e no t v i s i b l e u nde r t he se c ondi ti ons .

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" ~ ' .,2 ^ '! ~ ,~ U V V L _ ~ _ J ~ L20 25 30 3 5 4 0M i n u t e s

F i g u r e l B . D B - I E C D C h r o m a t o g r a m s fo r A r o c lo r s 1 2 4 8 , 1 2 5 4 , 1 2 6 0 , a n d 1 2 6 2 . C o n d i t i o n s w e r e a sd e s c r i b e d f o r F i g u r e 1 A .

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T a b l e 2.

DB1 C I IUPAC Con gene r A12 21Peak # # I.D. T o t . H o r n . T o t . H o r n . T o t . H o r n . T o t . H o r n . T o t . H o r n . T o t . H o r n .

613Cong ene r and We igh t Pe rcen t D is t r ibu t ions in DB-1 Peaks fo r E igh t A roc lo rs (a )Wt % o f Q uan t i f i ab le Peaks in A roc lo rs ( To ta l i n Peak; To ta l fo r e a c h H o m o l c }

A 1 2 3 2 A 1 0 1 6 A 1 2 4 2 A 1 2 4 8 A 1 2 5 4 A 1 2 8 0 A1262

11 3 3 0 2 4 612 2 11 3-3 #13 2 12 34 C C13 2 13 3-4 1.34 1.0914 2 15 4-4 4.00 3.66 4.95 2.5914 3 18 25-2 C .341 5 3 17 2 4 - 2 #1 6 3 2 4 2 3 6 C1 6 3 2 7 2 6 - 3 #17 3 16 2 3 - 2 .891 7 3 32 2 6 - 4 C1 9 3 2 3 2 3 51 9 3 3 4 3 5 - 21 9 4 5 4 2 6 - 2 6 ., ., .,

C C# #C 5.93 C 3.19 # ND

C 2.36 12.84 6.91 10.17 6.98 2.95 2.953.70 5.93 4.57 1.22

C C C.75 .78 .83 #

2.30 6.20 5.14 1.62C C C C

# #

##

.682 4 3 28 2 4 - 42 4 4 5 0 2 4 6 - 22 5 3 20 2 3 - 32 5 3 21 2342 5 3 33 34-225 4 53 25-2626 3 22 23-426 4 51 24-2627 4 45 236-22 8 3 3 6 3 5 - 32 9 4 46 2 3 - 2 63 0 3 3 9 3 5 - 4I31.1 4 52 2 5 - 2 53 1 . 1 4 6 8 2 4 6 - 33 1 . 2 4 7 3 2 6 - 3 53 2 4 4 3 2 3 5 - 23 2 4 4 9 2 4 - 2 5!33 3 3 8 3 4 53 3 4 4 7 2 4 - 2 43 4 4 4 8 2 4 5 - 23 4 4 75 2 4 6 - 43 5 4 6 2 2 3 4 63 5 4 s 5 2 3 5 6

~ . ~ 3.80 3.80 9.79 9.79 8.01 8.01 6.09 6.09 .69 .69N D N D ND ND ND N D

C C C C C

89 .89 2.74 2.74 7.63 6.83 6.28 5.95 2.78 2.11ND ND C .80 C .33 C .76

.79 .79 1.41 1.41 3.38 3.38 2.88 2.79 1.60 1.34ND ND # ND C .09 C . .26

# .83 1.20 1.10 1.17# .75 .80 .84

C C C# 1.36 3.35

N D N D# .83 .83 1 . 17 1 .17# .98 1.79

C2.63

NDI. I0 I . I01.48

C4.59 1.28

ND2.55 2.55 #2.19 #

.69 .47C .22

2 1 1 2 42.24 20.48 # #3 1 2 3 2.62 1.734 1 3 4 20.66 9.13 # #5 2 4 2-2 6.34 5.23 3.70 2.745 2 I 0 2 6 C C C C6 2 7 2 4 C C C C6 2 9 25 2.49 1.82 1.05 1.027 2 6 2-3 2.99 2.34 1.55 1.348 2 5 23 C C C C8 2 8 2-4 12.88 10.67 8 .94 6 .~ #9 2 14 3510 3 19 26 -2 # .79 .97 .96 #

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614T a b l e 2 . co n t i n u e dDB1 C I IUPAC Cong ene rPeak # # I . D .3 6 3 3 5 3 4 - 337 .1 5 1o4 24 6 - 263 7 . 2 4 4 4 2 3 - 2 53 8 3 3 7 3 4 - 43 8 4 4 2 2 3 - 2 43 8 4 5 9 2 3 6 - 33 9 4 4 1 2 3 4 - 23 9 4 6 4 2 3 6 - 43 9 4 7 1 2 6 - 3 43 9 4 7 2 2 5 - 3 54 0 4 o8 2 4 - 3 54 1 5 9 6 2 3 6 - 2 64 2 4 4 0 2 3 - 2 34 3 4 5 7 2 3 5 - 34 3 5 1o3 2 4 6 - 2 54 4 4 58 2 3 - 3 54 4 4 67 2 4 5 - 34 4 5 l o g 2 4 6 - 2 44 5 4 6 3 2 3 5 - 44 6 . 1 4 7 4 2 4 5 - 44 6 . 1 5 9 4 2 3 5 - 2 64 6 . 2 4 e ; 2 3 4 54 7 4 7 0 2 5 - 3 448 .1 4 66 2 4 - 3 448 .1 4 76 34 5 -24 8 . 1 5 9a 2 4 6 - 2 34 8 . 2 4 ao 3 5 - 3 54 8 . 2 5 93 2 3 5 6 - 24 8 . 2 5 9 5 2 3 6 - 2 54 8 . 2 5 1 0 2 2 4 5 - 2 64 8 . 3 5 aa 2 3 4 6 - 24 9 4 55 2 3 4 - 34 9 5 91 2 3 6 - 2 449 5 121 24 6 -3 55 0 4 56 2 3 - 3 4

150 4 6 0 2 3 4 - 4Ii5 1 5 8 4 2 3 6 - 2 35 1 5 9 2 2 3 5 - 2 55 1 6 15 5 2 4 6 - 2 4 65 2 5 8 9 2 3 4 - 2 65 3 5 9 0 2 3 5 - 2 45 3 5 1 0 I 2 4 5 - 2 55 4 4 7 9 3 4 - 3 55 4 5 99 2 4 5 - 2 454 5 113 23 6 -3 55 5 5 11 9 2 4 6 - 3 45 5 6 15o 2 3 6 - 2 4 656 .1 4 7s 3 4 5 - 35 6 . 1 5 8 3 2 3 5 - 2 356 .1 5 112 2 35 6 -35 6 . 2 5 I o a 2 3 4 6 - 357 .1 5 97 2 4 5 - 2 35 7 . 1 6 1 52 2 3 5 6 - 2 6

Wt % o f Quan t i f i ab le Peaks in A roc lo rs ( To ta l i n Peak; To ta l fo rA 1 2 21 A 1 2 3 2 A 1 0 1 6 A 1 2 4 2 A 1 2 4 8 A 1 2 5 4 A 1 2 6 0 A 1 2 6 2r o t . H o r n . T o t . H o r n , T o t . H o r n . T o t . H o r n . T o t . H o r n . T o t . H o r n . T o t . H o r n , T o t . H o r n# # #

# 1.55 4.17 3.26 5.00 2.12# 1.58 .91 C NQ 3.32 1.94 C NQIC C .67 2.88 NQ C 1.38 2.91 NQC C C CC C C C C# 1.47 3.78 3.11 6.10 .93C C C C C C

# #.90 1.01 1.18 ## # #

C C C# # # #

#1.00 1.00

N D

# 1.63# 1.72 1.72

# # .78 #.68 .68 1.60 1.60 4.50 4.5C .87 .87

ND ND ND ND.75 3.41 7.55 3.17.81 .81 3.62 3.47 9.63 8.65 @95 2,61

C

#

C1.27.70C

C.75

.70

# @6 6 # @6 6 .15 @6 6 .98 7.59 4.98 2.35C C C C

ND.70

ND ND ND.70 .70 .83 .83 1.08 1.08

c c c2.51 5.34 .81

.76 .76 1.o6 1.o6 3.58 3.58 .63c c c c

N D N D N D# # #C C C C

.88 2.07 8.38 3.09ND ND ND.74 .74 1.76 1.76 2.96 2.96

# #

1.15 1.15

c1.32

# # .7 7

.69 .69ND

.72 .721 1.05 1.05 2.19 2.19ND ND ND

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T a b l e 2 . co n t i n u e dD B1 C I IU P AC C o n g e n e r A 1 2 2 1 A 1 2 3 2Peak # # I .D.5 7 . 2 5 5 6 2 3 4 5 - 258 .1 4 81 34 5 -45 8 . 1 5 8 7 2 3 4 - 2 55 8 .1 5 I ; 7 2 3 5 6 - 458 .1 5 125 345 -2658 .2 5 111 2 35 -355 8 . 2 5 1 1 5 2 3 4 6 - 45 8 . 2 5 1 18 2 3 4 5 65 8 . 2 6 1 45 2 3 4 6 - 2 65 9 5 8 5 2 3 4 - 2 46 0 4 7 7 3 4 - 3 46 0 5 12o 2 4 5 - 3 56 0 6 1 3 6 2 3 6 - 2 3 66 1 5 1 1 0 2 3 6 - 3 4 3 8 . 786 1 6 t 4 a 2 3 5 - 2 4 6 N D6 2 6 15 4 2 4 5 - 2 4 66 3 5 8 2 2 3 4 - 2 3 #6 4 6 1 51 2 3 5 6 - 2 56 5 5 1 2 4 3 4 5 - 2 56 5 6 1 3 5 2 3 5 - 2 3 66 6 6 1 4 4 2 3 4 6 - 2 56 7 5 I o 7 2 3 4 - 3 56 7 5 1 09 2 3 5 - 3 46 7 6 147 2 3 5 6 - 2 46 8 5 ;2 3 3 4 5 - 2 46 9 5 to e 2 3 4 5 - 36 9 5 1 1 8 2 4 5 - 3 4 . 74 . 746 9 6 13~ 2 3 4 6 - 2 46 9 6 149 2 3 6 - 2 4 5 N D7 0 6 14 o 2 3 4 - 2 4 67 1 5 1 1 4 2 3 4 5 - 47 1 6 1 3 4 2 3 5 6 - 2 371 6 143 2 3 4 5 - 2 67 2 5 1 2 2 3 4 5 - 2 37 2 6 1 3 1 2 3 4 6 - 2 37 2 6 1 3 3 2 3 5 - 2 3 57 2 6 ; 4 2 2 3 4 5 6 - 27 3 6 1 4 6 2 3 5 - 2 4 57 3 6 16 5 2 3 5 6 - 3 57 3 7 ; 5 5 2 3 5 6 - 2 4 67 4 5 1 0 5 2 3 4 - 3 4 .72 .727 4 6 132 2 3 4 - 2 3 6 N D7 4 6 ; 6 ; 2 3 4 6 - 3 57 5 6 1 5 3 2 4 5 - 2 4 57 6 5 f2 7 3 4 5 - 3 57 6 6 ; 6 5 2 4 6 - 3 4 57 6 7 I5 4 2 3 4 6 - 2 4 67 7 6 1 41 2 3 4 5 - 2 57 8 7 17 9 2 3 5 6 - 2 3 67 9 6 1 3 7 2 3 4 5 - 2 48 0 6 1 3 0 2 3 4 - 2 3 58 1 7 1 7 6 2 3 4 6 - 2 3 6

615Wt % o f Quan t i f i ab le Peaks in A roc lo rs ( To ta l i n Peak; To ta l fo r eac h Homo lo~ l )

A 1 0 1 6 A 1 2 4 2 A 1 2 4 8 A 1 2 5 4 A 1 2 6 0 A 1 2 6 2To t . Ho rn . To t . Ho rn . To t . Ho rn . To t . Ho r n . T o t . Ho rn . T o t . Ho rn.

N D N D N D N D ND.70 .70 .78 .78 1.35 1.351 4.00 4.00 .66 .66 #

@87 @87 08 7 @87

.71 1.25 1.33@110 # ~110 #i @110 NDOII0 # O110 ~ 01 10 NDI 1.53 .90 .9C

1.00 1.00 2.73 2.73 9.00 9.00 1.47 1. 47 1.04 1.04ND ND

.69 .85 1.01# .89 3.10 3.01# C .38 ND ND

1.13 .75 1 .18 1.18 .92 .92~6 7 .14 1.18 .92

# .85 .721

.80 .80 2.35 2.3 5 10.45 7.12 C .95 C .71ND # ND C 3.33 10.30 9.35 7.70 6.99

# .30 ND bid.78 .48 .64 .64 .63 .63

#

C# #C C

.80 .8C 1 .16 1.16 .80 .8CND ND.74 .74 1. 82 1.82 C 1.51 # ND

ND # biD 3.98 2.47 2.73 2.73 @153N D

1.01 2.49 1.60# 2.08 3.03

.74

.74 ## # .85

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61 6T a b l e 2 . co n t i n u e d

DB1 C I IUPAC Con gene rPeak # # I .D.8 2 6 1 3 8 2 3 4 - 2 4 58 2 6 1 6 3 2 3 5 6 - 3 48 2 6 ] 6 4 2 3 6 - 3 4 58 3 6 ] 5 8 2 3 4 6 - 3 48 3 6 1 6 o 2 3 4 5 6 - 38 3 7 7 6 6 2 3 4 5 6 - 2 68 4 5 1 2 6 3 4 5 - 3 48 4 6 | 2 9 2 3 4 5 - 2 38 5 6 t 6 6 2 3 4 5 6 - 48 5 7 17 8 2 3 5 6 - 2 3 587 .1 7 17 5 2 3 4 6 - 2 3 58 7 . 2 6 16 s 2 3 4 5 - 3 58 8 7 1 a 2 2 3 4 5 - 2 4 68 8 7 18 7 2 3 5 6 - 2 4 58 9 6 12 8 2 3 4 - 2 3 48 9 6 1 62 2 3 5 - 3 4 59 0 7 1 8 3 2 3 4 6 - 2 4 591 6 167 2 4 5 - 3 4 59 2 7 18 5 2 3 4 5 6 - 2 59 3 7 17 4 2 3 4 5 - 2 3 69 3 7 18 1 2 3 4 5 6 - 2 49 4 7 1 7 7 2 3 5 6 - 2 3 49 5 6 1 5 6 2 3 4 5 - 3 49 5 7 1 7 1 2 3 4 6 - 2 3 49 6 6 1 5 7 2 3 4 - 3 4 59 6 8 2 0 2 2 3 5 6 - 2 3 5 69 8 7 1 7 3 2 3 4 5 6 - 2 39 9 8 2 0 1 2 3 4 6 - 2 3 5 61 0 0 7 1 7 2 2 3 4 5 - 2 3 51 0 0 8 2 o4 2 3 4 5 6 - 2 4 6101 7 t 9 2 2 3 4 5 6 - 3 51 01 8 1 9 7 2 3 4 6 - 2 3 4 61 0 2 7 1 8 0 2 3 4 5 - 2 4 51 0 3 7 1 9 3 2 3 5 6 - 3 4 51 0 4 7 1 9 1 2 3 4 6 - 3 4 5105 .1 8 200 2 3 4 5 6 - 2 3 61 0 5 . 2 6 t 6 s 3 4 5 - 3 4 51 0 6 7 17 0 2 3 4 5 - 2 3 41 0 7 7 19 0 2 3 4 5 6 - 3 41 0 8 8 1 9 8 2 3 4 5 6 - 2 3 51 0 9 8 1 9 9 2 3 4 5 - 2 3 5 61 1 0 8 1 9 6 2 3 4 5 - 2 3 4 61 1 0 8 2 0 3 2 3 4 5 6 - 2 4 51 11 7 1 8 9 2 3 4 5 - 3 4 51 1 2 8 19 5 2 3 4 5 6 - 2 3 41 1 3 9 2 0 8 2 3 4 5 6 - 2 3 5 6

1 1 4 9 207 2 3 4 5 6 - 2 3 4 61 1 5 8 19 4 2 3 4 5 - 2 3 4 51 1 6 8 20 5 2 3 4 5 6 - 3 4 51 1 7 9 266 2 3 4 5 6 - 2 3 4 51 1 8 1 0 2 o 9 2 3 4 5 6 - 2 3 4 5 6

Wt % o f Quan t i f i ab le Peaks in A roc lo rs ( To ta l in Peak; To ta l fo r each Ho mo lo )A 1 2 21 A 1 2 3 2 A I O 1E A 1 2 4 2 A 1 2 4 8 A 1 2 5 4 A 1 2 6 0 A 1 2 6 2T o t . H o r n . T o t . H e m . T o t . H o r n . T o t . H e m . T o t . H e m .# .78 6.20 10.70 5.01

C C C CC C C

1.00 1,00 # #N DN D

# .71 .71 ## .90 1.11

# #

# .61 5.22 8.85# 1.39 # #

# 3.10 3.10.65 #.72 .88.63 4.63 6.02.59 2.51 2.61.94 .89 C .68 # NE

C .05 1.72 1.04 1.04 1.0zC N(:

# # 1.07 1.0~# ## .85

.59 .59 .93 .93 .82 .82ND ND NE

# #.74 11.10 14.01# #

# ## .83

3.76 2.65.94 .87

# #

.65#

1.66 4.97C C

2.09 5.17#. 88 1 . 25# #

1.65 3.60# #31 1.30

I I * , !, I l l l i I / - 1 T * l ~ ~ - I d ~ ~ * I i . | [ i ' l l [ i l l ~ 'T ~ [ I ! [ i ' i l [ i | I [ i ' i l t , ] ' 1 1 [ I t ' l l i [ l ' l | I | | l ~ i l

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6 1 7(a) - Ke y to Conventions, Symbols and Abbreviations in Ta ble 2:Peak 1 in the 118 peak num bering system is biphenyi (not listed in the table). See text for determination o f the amount o fbiphenyl in Aroclors 1221 and 1232.Congener IUP AC numbers in the larger boldface font were present in at leas t one of the Aroclors a t or abov e 0 .05 wt % .Those in small italic print were absent o r present at < 0.05 w t %Congener d esignations denote the positions o f the chlorine atoms on each ring o f biphenyl and the hy phen representsseparation of the rings.Tot . column for each Aro clor lis ts the to tal wt % of al l congeners in each peak. as determined by G C /E L C DHem . column for each A roclor lis ts wt % value s of d ifferent homologs in each peak as determined by G C-M S in scan mode.# indicates that more sensi t ive GC-MS-SIM or GC-ECD analyses have determined that the peak or congener is presentbetween 0.05 and 0.5 wt %.C indicates that the congener contributes to the to tal wt % displayed for the major congener in a peak, and is above 0 .05 wt%. Wlam C is combined with # and no w t % is g iven, # is the major component , and the to tal wt % of the peak is _> 0 .05 %but < 0 .5 wt %.@ IU PA C# indicates that the congener du ted in a different peak in this particular Aroclor. Its observed elation position isindicated by the IUP AC # of the congener with with i t elated . See text for more detai ls .N D indicates that the coelating homolng (congener of d iffereat CI number) was n ot detected by ful l -scan GC -M S.N Q indicates that the coelut ing homolog was present , but was not quantif iable due to in terference from CF loss fragmentsfrom higher coehiting homoings.

C o m p r e h e n s i v e Q u a n t i t a t i v e C o n g e n e r - S p e c i f ic W e i g h t P e r c e n t D a t a fo r E i g h t A ro c l o rs . Ta b le 2g i v e t w o c o l u m n s o f w e i g h t p e r c e n t i n f o rm a t i o n f o r e a c h o f t h e e i g h t A r o c l o r s. T h e f ir s t g i v e s t h e t o t a l w e i g h tp e r c e n t o f t h e P C B c o n g e n e r s i n e a c h p e a k a s d e t e rm i n e d b y G C - E L C D a n d i s p r i n te d o n t h e l in e o f t h ec o n g e n e r t h o u g h t t o b e p r e s e n t a t t h e h i g h e s t c o n c e n t r a t i o n i n t h e p e a k . P e a k s p r e s e n t a t < 0 . 5 w t % c o u l d n o tb e q u a n t i f ie d b y G C - E L C D b e c a u s e o f s e n s it iv i ty li m it a ti on s . H o w e v e r , w e u s e d s e m i - q u a n ti t at i v e d a t a f r o mG C - E C D a n d / o r G C - M S t o i d en t if y p e a k s t h a t a re p r e se n t a t > 0 . 05 w t % b u t < 0 . 5 w t % a n d h a v e i n d i ca t e dt h e s e b y t h e s y m b o l # o n t h e li n e o f t h e m o s t a b u n d a nt c o n g e n e r i n t h e p e a k . I n c a s e s w h e r e s e v e r a l c o n g e n e r sc o e l u t e i n a p a r t ic u l a r p e a k , w e h a v e i n d i c a te d t h o s e t h a t a r e p r e s e n t in e a c h A ro c l o r b y a w t % v a l u e , a C , o rt h e s y m b o l # o r @ . " C " i n d i c a te s t h a t a c o n g e n e r s i g n i fi c a n tl y c o n t r i b u t e s t o t h e t o t a l w e i g h t p e r c e n t f o r t h a tp e a k . " @ " i n d i c a t e s t h a t t h e c o n g e n e r i s p r e s e n t b u t c o e l u t e s w i t h a m a j o r c o m p o n e n t i n a p e a k d i f f e r e n t f r o mt h e o n e t o w h i c h i t w o u l d b e a s s i g n e d b y i t s r e t e n ti o n t i m e i f e l u t i n g b y i t se l f. S u c h i n s t a n c e s r e s u l t f r o md i s p ar a t e p r o p o r t i o n s o f c lo s e ly e lu t in g c o n g e n e r s a n d a r e i n d ic a t ed b y t h e c o n v e n t i o n " @ I U P A C # " w h e r e t h eI U P A C # i s t h a t o f t h e c o n g e n e r w i t h w h i c h i t a c tu a ll y e lu t e s a n d w i t h w h i c h i ts w e i g h t p e r c e n t a g e w a sc a l c u l a t e d . Ex a m p l e s o f th i s t y p e o f v a r ia t i o n i n e lu t i o n a s si g n m e n t a n d q u a n t i t a t io n m a y b e o b s e rv e d i n t h e p e a kp a i r s 4 8 . 1 / 4 8 . 2 , 6 0 / 6 1 , a n d 7 4 / 7 5 . C o n g e n e r s a s s i g n e d t o a p e a k w i t h o u t a n y fu r t h e r n o t a t i o n w e re n o t f o u n d t ob e p r e s e n t a t s i g n i f ic a n t l e v e l s i n t h a t p a r t i c u l a r A ro c l o r .

Fo r p e a k s w h e re t h e C J C -M S s c a n d a t a p ro v i d e d r e l a t i v e a m o u n t s f o r d i f f e r e n t h o m o l o g s e t s w i t h i n ap e a k , t h e w e i g h t p e r c e n t a g e s o f t h e h o m o l o g s o f e a c h c h l o ri n a ti d n l e v e l a re l i s te d i n t h e s e c o n d c o l u m n f o r e a c hA r o c l o r . T h e s y m b o l N D i n d ic a t es th a t t h e h o m o l o g w a s n o t d e t e c t e d b y G C - M S i n t h e s c a n m o d e . T h e r e a r es e v e ra l i n s t a n c e s w h e re a n a l y s i s o n a d i f f e r e n t c o l u m n p h a s e b y G C -S IM d e t e rm i n e d t h a t a p a r t i c u l a r h o m o l o gn o t d e t e c t e d i n s c a n m o d e w a s a c t u a l l y p r e s e n t a t le v e l s b e t w e e n 0 . 0 5 a n d 0 . 5 w t % . T h e s e a r e i n d i c a t e d b y t h es y m b o l # i n t h e f i r s t c o l u m n a n d N D i n t h e s e c o n d c o l u m n fo r t h e p a r t i c u l a r A ro c l o r ( s e e p k s 1 4 , 6 9 , a n d 7 4 i nA r o c l o r 1 2 4 8 a n d p k 2 6 i n A ro c l o r 1 0 16 ). F i n a ll y , i n s e v e ra l c a s e s t h e i n d i v id u a l p ro p o r t i o n s o f c o e l u t in g

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61 8hom ologs c ou ld n o t b e a c c u r a t e ly de t e r m ine d b y G C- M S b e c a u se o f i n te r f e re nc e fr om the c h lo r ine lo s sf r a gm e n t s o f t he h ighe r c oe lu ti ng ho~o log ( s ) . T he se i n s t a nc e s a r e i nd i c a te d b y t he sym b ol N Q ( e .g . s e e pk 38 ).

T he l i s t e d we igh t pe r c e n t va lu e s we r e c a l c u l a t e d a s pe r c e n t a ge s o f t he t o t a l G C - ELC D- m e a su r e d P CBc on te n t , no t a s pe r c e n t a ge s o f t he a c tu a l we igh t o f A r oc lo r . T he r e fo r e , f o r u se a s c a l ib r a t ion s ta nda r ds , thet a b u l a t e d P CB c onge ne r d i s tr i bu t ions o f the A r oc lo r 1221 o r 1232 s t a nda r ds shou ld b e m u l ti p l ie d b y 0 .88 3 a nd0 .938 , r e spe c t ive ly , t o c om pe nsa t e f o r t he a m ou n t s o f b ipheny l f ou nd i n t he se tw o A r oc io r s . I n a dd i t i on , wee s t im a te t ha t t he su m o f pe a k s > 0 .05% b u t no t q u an ti fi ab le b y G C - ELC D in a ny one A r oc lo r ra nge s f rom - 3 .5to 8 .7 w e igh t pe r c e n t . He nc e t he va lu e s f o r m a jo r c om pone n t s l i s t e d i n T a b l e 2 m a y d i f f e r f r om a m or e c om ple t ede t e r m ina t ion b y t h i s am ou n t

P C B H o m o l o g D i s t r i b u t i o n s o f E i g h t A r o c l o r s . H o m o l o g d i st ri b u ti o n s p r o v i d e a n o t h e r u s e fu l w a y o fana lyz ing PC B mix tures . Individua l Aro c lor s were manufac tured to conta in spec i f ied weig ht perce nts o f chlor ine ,e x c e p t f o r A r o c lo r 1232 , wh ic h wa s a b l e nd o f 1221 and 1242 (r ou gh ly 50 :50) , a nd A r oc lo r 1016 , wh ic h wa sm a d e b y d i s t il l a ti on f r om A r o c lo r 1242 t o r e m ove t he m or e h igh ly c h lo r ina t e d c onge n e r s T a b l e 3 shows t hehom olog we igh t pe r c e n t d i s tr i b ut i ons f o r e a c h o f the e igh t A r o c lo r sa m ple s t ha t we a na ly ze d

T a b l e 3 . C o m p a r is o n o f H o m o l o g D i s t r ib u t io n s in D i f fe r en t A r o c l o r s a n d D i f fe r en t L o t s o f A r o c l o r s

C I N o .W e ia h t % in A r oc lo r s De t e r m ine d i n T h i s S tu dy1221 1232 1016 1242 1248 1254 1260 1262

W e i a h t % i n A r o c l o r s ( R e f . 22)1016 1242 1254 1260

I 6 5 . 5 3 1 . 32 2 9 . 7 2 3 . 7 2 1 . 2 1 4 . 7 2 1 . 5 1 5 . 03 4 . 8 2 3 . 4 5 1 . 5 4 6 . 0 2 0 . 9 1 . 8 4 9 . 8 3 5 . 3 1 . 2 0 . I4 1 5 . 7 2 7 . 3 3 0 . 6 6 0 . 3 1 7 . 1 2 7 . 8 3 2 . 6 1 6 . 6 1 . 05 5 . 8 8 . 7 1 8 . 1 4 9 . 3 9 . 2 4 . 2 1 . 0 1 3 . 2 5 1 . 0 1 3 . 56 0 .8 27.8 46.9 30.9 0 .2 2 .4 23.9 47.07 3.9 36.9 45.8 0.2 4.4 33.88 6.3 17.7 0 .7 7 .59 0.7 1.3 0.710 0.1

D I S C U S S I O NW e ha ve p r e pa r e d c a l i b ra t ion t a b l e s t ha t a s s ign 135 c onge ne r s a nd 104 pe a k s t o t h e A r oc lo r s . T he

r e m a in ing 74 c onge ne r s ha ve b e e n a s s igne d t o e i t he r t he se 104 p e a k s o r t o 20 a dd i t iona l pe a k s t ha t a r e r e so lve don a DB - I c o lu m n. Ou r t a b l e s i nc lu de we igh t pe r c e n t d i s t r ib u t ions f o r a l l m a jo r ( > 0 .5 w t % ) P CB c om pone n t so f A r oc lo r s 1221, 1232, 1242 , 1016 , 124 8 , 1254 , 1260 , a nd 1 262 . A r oc lo r c om p one n t s p r e se n t b e twe e n 0 .05and 0 .5 w t % we re a l so ident if ied , bu t not quant if ied .

Ou r da ta for sam ples of the e ig ht Aroc lor s indica te tha t the re a re s ignif icant e r ro r s in cong ener ass ignmentsand in quanf i ta t ion in severa l r ecent ly publ i shed s tudies . In 1993 the Wor ld Hea l th Organiza t ion publ i shed acom prehen s ive tab le of the dis t r ibu t ions o f cong eners in Aroc lor s 1016, 1242, 1248 , 1254 and 1260 (37).

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6 19Unf or tu na te ly , t he se va lu e s we r e c o m pi l e d f r om e a r ly da t a ( 3 8 , 3 9 ) t ha t r e l i e d on d i f f e re n t s e t s o f pa c k e d o rc a p i l la r y G C c o lu m ns t o he lp r e so lve ~oe lu t ing c onge n e r pa i r s. W i th f e we r t ha n 50 i nd iv idu al c onge n e r s t a nda r dsa va i la b l e a t t ha t t im e , m os t a s s ignm e n t s o f c onge ne r s t o pe a k s we r e m a de f r om e s t im a te d r e t e n ti on t im e s b a se don s ingle r ing ha l f - re tent ion indices . A com par ison o f the A roc lo r cong ener d is t r ibu t ions in the W .H.O . tab lewi th t hose o f S c huLz e t a l. ( 2 3 ) and tho se rep or ted h ere indica tes many l ike ly misass ignm ents and quan t i ta tiveinaccurac ies in the W .H.O . tab le . Therefore , i t should not be used as a bas is for ca l ib ra t ing CQ CS ana lyses.W e f ou nd s im i la r d i s c r e pa nc ie s i n t a b le s o f m a jo r c ons ti t u e n ts o f A r oc lo r s 1242 a nd 1260 t ha t we r er e c e n t l y pu b li she d b y K r u pc ik e t a l . ( 1 7 ) . T he i r ta b l e o f A r oc lo r 1242 c ons t i tu e n t s p r e se n t a b ov e 0 .2 w t % om i t ss ix con gene rs tha t we rep or t a t ~ 0 .7 wt % , name ly cong eners 82, 85, 87, 91, 97, and 105. Con verse ly , the tab leinc ludes cong eners 69, 72, 76, and 113 (a lbe i t wi th no va lues l is ted) , bu t we found the se to he be lo w 0.05 w t %.T he t a b l e i s a lso m i s le a d ing in t ha t i t d oe s n o t c l e a r ly i de n t if y wh ic h c ong e ne r s c oe lu t e a nd doe s no t a s s ign va lu e sto d i f f e re n t c oe lu t i ng hom ologs . He nc e , c ong e ne r s 53 a nd 51 a r e l i st e d on a pa r w i th c oe lu t i ng c onge ne r s 33a nd 22 , whe r e a s ou r d a t a show tha t c onge ne r s 53 a nd 51 c ons t i t u te < 5% of t b e ir r e spe c t i ve pe a k s ( s e e DB- 1pe a k s 25 a nd 2 6 i n T a b l e 1 ) .

S e r iou s om i s s ions in t he t a b l e o f A r oc lo r 1260 c ons t i tu e n t s > 0 .4% pu b l ishe d b y Kr u p c ik e t a l. ( 1 7 ) raisee ve n m or e c onc e r n . T he t a b l e om i t s c onge ne r 153 whic h we r e por t a t 12 .2 w t % a nd whic h i s ge ne r a l l yr e c ogn ize d a s t he m os t s ign if ic a nt s i ng le c om pone n t i n A r oc io r s a nd t he one m os t f r e q u e n t ly r e por t e d . T h e t a b l ea l so om i t s c onge ne r s 172 , 177 , 195 , 199 , a nd 206 w hic h we f ou nd t o b e p r e se n t b e twe e n 0 .7 a nd 2 .5 w t % a ndg ive s no va lu e s f o r c onge ne r s 149 a nd 18 7 whic h we r e por t a s 3 .3 a nd 5 .2 w t % , r e spe c t i ve ly . Conver se ly ,cong eners 66, 123, 148 , 15 9, and 182 a re a l l l i s ted as major const ituents, hu t w e fou nd the m to be wel l be low0 .05 w t %.

T he d i sc r e pa nc i e s b e twe e n t he A r oc lo r 1242 a nd 1260 c ons t i tu t e n t s r e por t e d b y Kr u pc ik e t a l . ( 1 7 ) a n dt hose r e por t e d he r e a nd b y S c hu lz e t a l . ( 23 ) a r e t o o l a r ge t o he e x p l a ine d b y va r i a t i ons in A r oc lo r l o t s a nd a r emo re l ike ly due to con gen er misassignments , r epo r t ing omissions, and quan t i ta t ive inaccurac ies in the tab lespubl i shed in re f. 16. Consequently , the proced ure recomm ended by Kru pc ik e t a l . ( 1 7 ) f o r c om b in ing G C- FI Da nd G C - MS m e a su r e m e n t s o f A r oc lo r s t o su ppo r t the i r u se a s s e c onda r y s t a nda r ds is on ly a s good a s thea c c u r a c y o f the c on ge ne r a s s ignm e nt s a l l ows a nd shou ld b e u se d wi th c a u t ion .

T he on ly o the r CQC S d a t a f o r ind iv idu al A r oc lo r s a r e t hose de t er m ine d b y 2 - D G C f o r A r o do r s 1016,1242, 12 54, and 1260 ( 2 3 ) . How e ve r , La r se n ( 6 ) c a u t ione d i n a r e c e n t re v i e w tha t t he 2D - G C m e thod c a n m i ssa l l o r pa r t s o f som e c on ge ne r s i n pe a k s i f t he s e c o nda r y c o lu m n l a c k s su ff ic ie n t d i s c r im ina t i on , o r i f t b e he a r t c u t sa re not m ade exac t ly r ight . H e a lso pointed ou t tha t cong eners proven to be prese nt in s igni ficant am ounts inA r oc lo r s , su ch a s 71 , 163 , 43 a nd 102 a re no t l i s te d in t he 2D- G C t a b le s o f S c hu lz e t a l . We concur , and wef u r the r no t e t ha t we de t e c t e d su bs ta n ti al a m ou n t s o f c onge ne r s 1 14 , 124 a nd 144 t ha t we r e no t r e po r t e d b ySchuiz e t a l . T he r e f o r e , a l t hou gh t he S c hu lz ta b l e s a r e e x t r e m e ly va lu a b le f o r a n ove r v i e w o f A r oc lo r c onge ne rd i s tr i b u ti ons , t he y m u s t b e a p pr oa c he d wi th c a u t i on a s t he b a si s e r a CQC S P C B a na lys is c a l ib r a ti on .

I t i s impor tan t to recog nize tha t there ma y be s ignif icant var ia t ions in d i f fe rent lo t s o f the sam e Aroc lors .T a b l e 3 i l l u s t ra t e s d i f fe r e nc e s b e twe e n t he hom olog d i s t r i b u ti ons t ha t we r e por t f o r t h e A r o c lo r s a nd t hose t ha tc a n b e c a l c u l a te d f o r A r oc lo r s 1016 , 12 42 , 1254 , a nd 1260 f r om the 2 - D G C t a b l e s o f S c hu lz e t a l . ( 2 3 ) .Und ou b te d ly som e o f the se d i f f e r enc e s a r e d u e t o t he d i ff e r en t m e thods o f ana lys is , hu t o the r s a r e m os t l i k e lydu e t o d i f fe r e nc e s i n t he pa r t i c u l a r A r o c lo r l o t s a nalyze d . T hu s i t i s im por t a n t t ha t t h e A r oc lo r lo t s u se d f o r a

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6 2 0secon dary ca l ib ra tion s tandard be w el l -matched to tho se f rom w hich the publ ished w eight pe rcent d ist ribut ionswe r e de t e rm ine d .

Ou r e igh t A r o c lo r s t anda r ds , t oge the r w i th t he c onge ne r d i s t r ib u t ions in T a b l e 2 , p r ov id e m u c h g r e a t e rf lex ib i li ty than th e s ingle f ixed mix tures used by m ost o ther m ethods (13 , 14, 15, 19) . Si te - spec i f ic cus tomizeds tandards can eas i ly be c rea ted by mix ing the individua l Aroc lor s in var ious propor t ions to match thechrom atograp hic pa t te rns observe d a t individua l s ites . In ins tances wh ere a par t icu la r Ar oc lo r d is t r ibu tion hasunderg one m ajor a l te ra t ion, inc luding the pro duc t ion o f unusua l dechlor ina tion prod uc ts , the s tandard can bef u r the r c u s tom ize d b y t he a dd i t i on o f t he c on ge ne r s ob se r ve d a s de c h lo r ina t i on p r odu c t s (10) .

CQC S P CB a na lys is m e thods u s ing ou r A r oc lo r s t a nda r ds and t he va lu es in T a b l e 2 ha ve b e e n e m ploye din a number of publ i shed s tudies (25-34) . Ou r com ple te peak ass ignment tab le makes i t poss ib le to measurem inor A r oc io r pe a k s a nd non- A r oc lo r pe a k s ( su c h a s de c h lo r ina t i on p r odu c t s ) b y c a l i b r a t i ng a ga ins t pu r econg ener s tandard s run sepa ra te ly or b y us ing tab les of r esponse fac tor s co r rec ted for the ac tua l ins trument be ingused. Tw o recen t PC B dechio r ina t ion s tudies tha t r e l ied on o ur weigh t percent tab les wi th such supplementat iona t t e s t t o t he i r a c c u r a c y b y de m ons t r a t i ng t ha t t he c a l ib r a ti ons b a se d on t he se t a b l e s pe r m i t t e d s t o i c h iom e t r ic m a ssb a l a nc e s f o r pa r e n t c ong e ne r s a nd t he i r de c h lo rina t ion p r odu c t s (33, 34) .There i s s t il l a need for r eadi ly ava ilable A roc lo r ca l ib ra t ion s tandards for CQ CS PC B ana lyses. Idea l ly ,these wo uld cons is t of a se t of individua l Aro c lor solu t ions cover ing the fu ll rang e o f con gen er d ist ribut ions ;namely, Aro c lor s 1221, 124 2, 1248 , 125 4, 1260, and 1262, for which the weig ht percen t d is t ribu t ions o f a l lcong eners prese nt a t o r abo ve 0 .05% have been c are fu l ly de te rmined by s ta te -of - the-a r t mul ticolumn/mul ti -de t e c to r m e thods a ga ins t p r im a r y s t a nda r ds o f a l l c onge ne r s f ou nd i n t he A r oc lo r s . T he se A r oc lo r so lu t i onsshould remain ava i lab le ove r a long dura t ion tog e ther wi th the i r weight percen t d is t r ibu t ions .

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