The Computer-Assisted Interpretation of Copolymer Mass Spectra

Transcription

1 Th Cmptr-Assistd trprtati f Cplymr Mass Spctra Pal O. Dais ad Fracis J. Hby Rsarch Labratris, Rhm ad Haas Cmpay, Sprig Hs, Psylvaia, U.S.A A cmptr prgram calld MSCOPOL has b dvlpd t aid i th itrprtati f cplymr mass spctra. Th prgram rads th mass spctrm, calclats th mst likly mmr masss via crrlati r Frir trasfrm mthds, dtrmis pssibl d grp masss basd th mmr masss, ad ca th sarch mmr ad d grp data bass fr likly chmical mitis. Rfimt f th d grp rslt is pssibl by calclati f th mmr rati ad dgr f plymrizati as a fcti f d grp mass. Th prgram is writt i Micrsft Visal Basic ad rs a BM cmpatibl PC. Applicatis ar shw fr plystyr, ply(n-viyl pyrrlid/viyl actat), ad ply(thyl xid/prpyl xid). (] Am Sc Mass Spctrm 1995, 6, ) W 'ith th sit f aalytical mass spctrmtry mthds crrtly availabl, prdcti f itact iizd mlcls frm plymric matrials has bcm rti. Sft iizati tchiqs sch as fild dsrpti [1-3], fast-atm bmbardmt [4, 5], lasr dsrpti [6, 7], scdary i mass spctrmtry [8, 9], ad matrix-assistd lasr dsrptiiizati [10-12] allw t btai mass spctra that shw th distribti f mlclar is f a sythtic plymr. Wh th idividal mlclar is ca b mass rslvd frm athr, th th spctrm yilds ifrmati with rgard t th mmr ad d grp masss as wll as th dgr f plymrizati. Th advatag f mass spctrmtry vr thr tchiqs f plymr aalysis, sch as ifrard ad clar magtic rsac spctrscpis [13] is that fr lw mlclar wight matrials th distribti f mass as wll as th mmrs ad d grps f th plymr ar dtrmid i th sam masrmt. Th spctra ca b rlativly simpl as i th cas f a hmplymr whr a pattr f paks ar sparatd by th mass f th mmr. Altrativly, wh mr tha mmr is sd i th prparati f th plymr th spctra ar mr cmplicatd ad th cmpsitial ifrmati is mch mr difficlt t xtract. Fr a cplymr mlclar i th qatitis that mst b dtrmid ar th mass f th mmrs, th mbr f ach mmr, ad th mass f th d grps. Bcas a limitd mbr f mmrs ad d grps ar actally prst i mst plymrs, kwldg f th mass ft is sfficit t ccld its cmpsiti. This ifrmati is f grat tility fr fdamtal drstadig f ply- Addrss rprit rqsts t Dr. Pal O. Dais, Rsarch Labratris, Rhr ad Haas Cmpay, 727 Nrristw Rad, Sprig Hs, PA Amrica Scity fr Mass Spctrmtry /95/$9.50 SSD (95)00529-M mrizati mchaisms ad mmr ractivity, as wll t idtify th atr ad sythtic rts f kw matrials. T aid th itrprtati f ths spctra w hav dvlpd a prgram calld MSCOPOL t shw s th pssibl cmpsitis f th is. Althgh svral apprachs hav b tak fr th itrprtati f plymr mass spctra [14-16], th mthd prstd hr is iq i that assmptis ar mad abt th mass r mbr f th mmrs ad d grps. Similar t th wll kw mass spctrmtry sftwar tls f prbability basd matchig (PBM) ad slftraiig itrprtativ ad rtrival systm (STRS) [17], MSCOPOL was dvlpd t b applicabl t th ttal kalw. Th algrithm w hav dvlpd will rad th mass spctrm, fid th mst likly mmr ad d grp masss, ad sarch a data bas fr pssibl mmrs ad d grps. t is writt i Micrsft Visal Basic fr DOS ad rs a BM cmpatibl prsal cmptr. Exprimtal Masrmts wr prfrmd a JEOL HX-110 mass spctrmtr with a acclrati pttial f 10 kv, mass rslti f 1000 at 10% vally, ad dtcti f psitiv is. Fr fild dsrpti (FD) masrmts, apprximatly 1 /~L f = 1% wt/v slti f th plymr was dpsitd th carb mittr. Th plystyr was disslvd i tl. Th ply(thyl xid/prpyl xid) was disslvd first i watr ad th xtractd with mthyl chlrid t rdc th amt f sdim i th sampl. This hlps sr that iizati by prtati prvails vr sdim cati attachmt. A 11.5 kv dsrpti pttial was applid with mittr hatig 0-25 ma at 1-2 ma/mi. Th istrmt was scad frm 100 Rcivd April 3, 1995 Rvisd J 19, 1995 Accptd J 26, 1995

2 J Am Sc Mass Spctrm 1995, 6, COMPUTER NFERPRETATON OF POLYMER SPECTRA 1113 t 3000 i 20 s ad th spctra shw ar th sm f svral scas. Fr fast-atm bmbardmt (FAB), plymr was disslvd i act ad mixd with 3-itrbzyl alchl matrix th prb. Sampls wr iizd with a 6-kV X atm bam ad th istrmt was scad as bfr. Th plystyr f avrag mlclar wight 580 was btaid frm Plymr Labratris, c. (Amhrst, MA) th ply(thyl xid/prpyl xid) mlclar wight 1100 was frm Plyscics, c. (Warrigt, PA), ad th ply( N-viyl pyrrlid/viyl actat) 60/40 cplymr f avrag mlclar wight 2400 was frm Scitific Plymr Prdcts, c. (Otari, NY). Th MSCOPOL prgram was r frm th DOS virmt a BM cmpatibl prsal cmptr with 16 MB f radm accss mmry with a 486/66- MHz prcssr; als it ca b r frm a Widws virmt. Th prgram rqirs at last 512-kB mmry, < 1-MB disk spac, ad a miimm prcssr f Traslati ad rcmpilati wld allw it t b sd a Macitsh r VAX systm. Mathmatical Slti Giv a cplymr mad f tw mmrs f mass M ad M 2 th mlclar wight f a plymr mlcl, M, is qal t th sm f th masss f its mmr its ad f its d grps, END: M = END + l.m + 112"M 2 (1) T flly dscrib ach plymr mlcl ds t dtrmi th mmr masss, th d grps mass, ad th mbr f mmr its, 1 ad ii 2. Th dgr f plymrizati is a cmm trm fr 771 ad ;7 2 Th masss f th mmrs ar dtrmid by traslati f th spctrm + r - DELTAM mass its ad crrlati f th abdacs f th traslatd spctrm with ths f th rigial spctrm. Th highst crrlati cfficits aris with traslatis that satisfy th qati DELTAM = Jl " M1 + J2" M2 (2) whr Jl ad J2 ar itgral. Grally th highst crrlati cfficits crrspd t Ji = -1, 0, r +1. A mmr databas is availabl t sarch fr mmrs f mass DELTAM. Altrativly, th mmr masss ca b idtifid by sig a Frir trasfrm algrithm. Th mass spctrm f a plymr csists f a sris f is rglarly spacd vr th mass-t-charg rati axis. A Frir trasfrm algrithm shld, ths, yild sm ifrmati abt this pridicity that is dirctly rlatd t mmr masss. Th thry tlls s that th Frir trasfrm f a Dirac cmb f pridicity M is a sigl Dirac pak dlta(/m) [18]. Th algrithm icldd i this prgram calclats th fast Frir trasfrm (FFT) f th spctrm ad plts th mdls f ach Frir trasfrm datm pit vrss th rciprcal f its abscissa. Fr th aalysis f th d grps i a liar plymr, ca ly dtrmi th sm f th masss f bth d grps bcas fragmtati f th mlcl ccrs that wld allw diffrtiati f th tw ds f th mlcl. Fr liar plymrs th cas is smwhat mr cmplicatd bcas thr r mr d grps wld b prst. Th gral slti fr d grps is dtrmid by rwritig q 1 as fllws: r whr M - END = l'm 1 + 2"M 2 (3) M- END = GCD.(Z 1 -}-/12 Z2) (4) Z i = Mi/GCD (5) GCD is th gratst cmm dmiatr f M 1 ad M 2. Dividig bth sids f q 4 by th gratst cmm dmiatr givs (M - END)/GCD = ;71 - Z 1 + ii 2. Z 2 (6) Bcas ll, H2, El, ad Z 2 ar all psitiv r ll itgrs (M - END)/GCD mst b a psitiv r ll itgr; thrwis said M - END mst b a mltipl f GCD. Hc, fr a giv mlclar mass, th sm f th masss f th d grps ca ly tak vals that satisfy qs 7 ad 8: M = Z.GCD+ R (7) END = R + k. GCD (8) whr th k is a psitiv r ll itgr ad qatity Z is th rslt f th itgral divisi f M by GCD with R as th rmaidr. Ths, q 9 ca rplac q 1: Z-k = ;h'z1 +;72'Z2 (9) Ovr th tir spctrm, q 8 ca yild svral vals fr R, which will b calld rt d grps. This mas that diffrt d grps ar prst. Th istpic distribti itrfrs with th d grps as wll t grat mltipl R vals. Masss that yild diffrt R vals mst b ivstigatd sparatly. Mrvr if x is a pssibl d grp, x + pl.ml + P2 " M2 is als a pssibl d grp, whr Pl ad P2 ar itgrs. Th d grps f mass lwr tha th lwst mass mmr (pl = P2 = 0) frm a spcial class f d grps that cat b frthr rdcd. Ths sltis ar calld basic d grps ad ar th tpt giv by th prgram ad shw i th fllwig txt. Th actal d grp mass ca smtims b

3 1114 DANS AND HUBY J Am Sc Mass Spctrm 1995, 6, drivd frm a basic d grp aftr th additi f r tw mmr it masss. Fr th dtrmiati f th mmr cmpsiti f a mlcl, th lwr mass rgi (grally < m/z 5000) is th mst sfl. A giv M, END pair r Z, k pair admits sltis f th frm f a tw-dimsial vctr ( 1, 2). A sigl pair ca hav may sltis bcas a vctr ( 1 + j- Z2, 2 - j- Z l) is als a slti. Hwvr, if j. Z~ is largr tha 2, th slti will ivh, gativ cmpts ad, ths, bcm satisfactry. Als if Z > Z~.Z 2, thr is ad ly slti vctr (~, 2), ad th mst valabl ifrmati is ctaid i th masss lss tha GCD-Z.Z 2 r M.M2/GCD. Ths, byd this mass, M1.M2/GCD, thr ar mltipl sltis fr ( l, 2) which ca satisfy th spctrm. Dscripti f th Cmptr Prgram Th cmptr algrithm traslats th spctrm DELTAM its ad dtrmis th crrlati as a fcti f DELTAM t yild pssibl mmr masss. Th mass f th d grps is th sh, d as th prgram gs thrgh all th pssibl cmbiatis f k, ~, ad 2 ad stimats what prprti f th ttal abdac f th spctrm is acctd fr by ach val f k. Tabls ad graphic tpt hlp th itrprtr. Smtims svral vals f k satisfy 100% f th abdac ad thr csidratis hav t b tak it acct t dtrmi th d grps. Smtims f th vals f k ca acct fr all th abdac d t th prsc f svral d grps sms. Th cplymr mass spctra prgram m has svral ptis: Rad spctrm, which rads th tablatd spctrm frm th PC disk. Mmrs, which dtrmis th prbability f varis mmr masss that fit th spctrm. Ed grps, which dtrmis th prbability f varis d grp masss that fit th spctrm basd th mmrs dtrmid. stpic pattr, which ss mmr ad d grp istpic distribtis t rfi th rslts. Cmpsiti, which ss th prcdig rslts t stimat th mmr rati i th cplymr. Databass, which ctais th mass, am, frmla, ad prcsss f cmmly sd mmrs as wll as mass, am, frmla, ad src f d grps. t is crrtly big pdatd t vr 250 mmrs. Rviw rslts, which lts viw tabls f rslts fr masss f mmrs ad d grps. Chmical csidrati ca b tak it acct t frthr slv th prblm. Th pssibilitis ca b gratly rdcd by csidrati f chmical ifrmati, sch as lgical cmpsitis ad pssibl d grps frm kw iitiatrs ad chai trasfr agts. Oft a sigl ambigs rslt is t btaid. Hwvr, th gratst asst f this apprach is that all pssibilitis ar xamid i ctrast t th maal apprach i which th aalyst is ft satisfid wh a fit is fd, ad frthr iqiry is haltd. Svral ffcts that ca hlp rdc th prblm ar addct frmati, rasabl d grps, crrt d grps, istpic ctribtis, ad plymrizati prcss paramtrs sch as ractivity ratis [19, 20]. Th iizati prcss ft ccrs by frmati f a addct sch as a prt r a sdim r ptassim i bd t th mlcl. This has t b tak it csidrati wh th cmpsiti f th d grps is ivstigatd. Obvisly sm f th masss gratd by q 7 cat b th actal d grp. Th miimm d grp sm fr a MH + i gratd by FDr FAB is H + mass = 1, th H3 mass=3, th CH~ mass = 17, H3 O+ mass = 19, ad s frth. Thrfr, a basic d grp val ft mst b cmplmtd by a cmbiati f mmr its t yild a chmically ratial d grp sm. Althgh thr ar may catalysts ad chai trasfr agts availabl, ly a rlativly limitd st is cmmly sd. A list f ths agts ca b drivd frm th litratr, ad th prgram iclds a databas facility t str ad rtriv crrt plymr d grps ad thir rigi. Th istpic ctribti cat b glctd i th spctral itrprtati. f th mmrs ar sigificatly diffrt i cmpsiti, th istpic ctribti ca yild sm hlpfl ifrmati. Th spctra mst b crrctd t tak it acct th istpic ctribtis bfr abdac-basd cmptatis ar carrid t. Additially, fr a giv M, END pair, th cmptati f th iq slti vctr (l, 2) is pssibl ly fr mlclar masss lwr tha GCD.ZjZ 2 r (M1.M2)/GCD. This mas, fr istac, that with mmrs f thyl xid ad prpyl xid th maximm mlclar mass that will yild iq sltis fr 171 ad 2 is (44.58)/2 r With N-viyl pyrrlid ad viyl actat mmrs th val is (111.86)/1 r Hwvr, th limit is sally impsd by th rslvig pwr f th mass spctrmtr as ppsd t th mathmatics. High rslti masrmts wld icras this limit t largr mlclar masss bcas th GCD wld b rdcd t a fractial val. f th abdacs f ach pak ar kw, ca cmpt th mmr rati fr th tir sampl with gd prcisi. t is pssibl th t driv ifrmati th plymrizati prcss ad th mmr rlativ ractivity. Cvrsly, aftr mmrs ar dtrmid, th d grp mass rslt ca b rfid by csidrati f th distribti f 1 ad 2, bcas ths vals shld vary i a fashi csistt with plymrizati kitics [20]. O difficlty may ccr wh mathmatical cici-

4 J Am Sc Mass Spctrm 1995, 6, COMPUTER NTERPRETATON OF POLYMER SPECTRA 1115 t = b d B 50 jch m x '/8 b 68 d ii 68 c ~ 4~a L 6O0, 91 "i,~ ZOO 14 Figr 1. FD mass spctrm f plystyr 580. dcs ar prst sch as wh th mmrs hav th sam mass r wh th mass f is a mltipl f th thr. Althgh this may mak th itrprtati f th mmr masss mr difficlt, it will t hav a ffct th tcm fr th d grp. Rslts ad Discssi Th mthd is illstratd with a simpl cas f th FD mass spctrm f plystyr with mbr avrag mlclar wight f 580, shw i Figr 1. By applicati f th prgram fr th dtrmiati f mmr mass, th rslt i Figr 2 is btaid whr a pattr f paks is shw 104 apart. This is, f crs, th mmr mass f styr. Th rslt fr traslati f th spctrm by zr its is always f it crrlati. Th by trig 104 as th mmr mass, th d grp sm is displayd (Figr 3). Th val f 58 is rasabl as ar highr vals f 58 pls mltipls f 104. Th tr val is actally 58, bcas this matrial was prpard i a aiic mthd frm btyl lithim iitiatr. Th istpic ctribtis f ]3C i th mlclar i ar vidt frm th paks at m/z 59 ad 60 as wll as 163 C P rl O 48 8~1 ~ ~ ~ 24B 28~ (m.,,.z) Figr 3. Th pssibl d grp masss ad th prct f th spctrm i Figr 1 fr which thy acct. ad 164. With a d grp f 58 als ca ccld that th iizati ccrrd by lctr jcti ad t attachmt f a cati. Althgh t prst i this spctrm, tw ffcts that cld cmplicat th rslt ar mltipl chargig ad th prsc f atms with high rlativ abdac f istps, sch as chlri r brmi. f dbly chargd is had b prdcd, as ca ccr i fild dsrpti, th MSCOPOL wld yild mmr ad d grp masss f half th tr vals. Fr th cas f istpic ctribtis, additial paks wld b bsrvd i th rslts as bfr fr th 13C istps. Th FAB mass spctrm f ply(n-viyl pyrrlid/viyl actat) is shw i Figr 4 fr th rgi f m/z izati i FAB ccrs by attachmt f a prt r sdim cati t th mlcl. Th spctrm appars cmplicatd ad ctais may spcis f varyig cmpsiti ad mass. Th prgram ca rapidly ( < 1 s) rdc this ifrmati t giv th rslt shw i Figr 5 fr th mst likly mmr masss. Th val f m/z 86 crrspds t th mass f th viyl actat mmr, whras 111 is frm th N-viyl pyrrlid. Th m/z 112 is als larg bcas! d 6 J71 to5? -~-- CH2 CH ---~ CHz CH.~ - v"? i 6 a r Z ZO 142b l",ld 4 t-l -128 Figr 2. Figr '-40 g (m/-z) Th pssibl mmr masss fr th spctrm i l~~ t 4 ~ t OBO 2OOO N~Z Figr 4. Partial FAB mass spctrm f ply(n-viyl pyrrlid/viyl actat).

5 1116 DANS AND HUBY J Am Sc Mass Spctrm 1995, 6, ,2" r r 1!. ~,'f,.3 ~.~, Figr 5. Figr 4, i ztz J Th pssibl mmr masss fr th spctrm i f rdig f mass-t-charg vals d t istpic ctribtis ad mass dfcts, ad mst thr pssibilitis ar cmbiatis f ths vals. Th m/z 25 ad 26 ar th diffrc f th mmr masss, ad th 172 is th rslt f traslati f th spctrm by tw viyl actat its. Ths vals f 86 ad 111 ar th trd fr slti f th d grp mass with th rslt shw i Figr 6. Thr ar svral pssibl d grps vals, which mas that svral diffrt d grps ar prst i this plymr; sm ar chmically rasabl, sch as m/z 11 ad 22, which cld b basic d grps that, with th additi f a mmr it f 86 r 111, wld th hav chmically rasabl masss f 97, 108, 122, ad 133, rspctivly. Frm th spctrm f Figr 4, th ca ccld that th sm f th masss f th d grps pls ay addcti f H * r Na + is mst likly 36, 47, 61, 86, 97, r 111. Additially sic 100% f th abdac ca.t b acctd fr by f ths masss pls its assciatd istpic masss, th thr mst b mr tha d grp prst. 172 i 6; 2 s ~A 7?3 5 L, J.~iii,k... - ft. " - ~b " " ~2h - ~4h " " ~sh~ " Jz Figr 7. FD mass spctrm f ply(thyl xid/prpyl xid). Th FD mass spctrm f ply(thyl xid/prpyl xid) mlclar wight 1100 t, is shw i Figr 7. Th distribti xtds frm blw m/z 700 t abv 1700 with a maximm ard m/z t is radily appart frm th spctrm that a similar pattr f paks rpats vry m/z 58. t ths may b pssibl t maally dtrmi th mmr masss ivlvd i this plymr. Hwvr, wld hav t list th trial ad rrr mthd t pick pssibl masss ad s if thy fit. By applicati f th MSCOPOL prgram ths data ar rdcd rapidly t th tpt i Figr 8 which shw th pssibl mmr masss. Th m/z 58 is tim mst likly pssibility as wll as twic this val ad gativ vals f m/z -58 ad Additially, m/z 44 is appart with its assciatd cmbiatis with m/z 58, fr xampl, m/z -4 is d t m/z 58 mis 44. A additial rslt shw hr that is t bvis frm th mass spctrm is that althgh th prpyl xid, mass 58, is symmtrically distribtd with bth psitiv ad gativ vals, th thyl xid, mass 44, shws ly psitiv vals. This is itrprtd as big d t th mthd i which th plymr was prpard ad th rsltat strctr. Ths, i th sampl thr is A b~ 11 d a~18 c 38 :3s a ~z s? C r tl t.8 t Q 1.2" S S t16..h [!.l, g 28 48, 1 5g f, lh, B 14~ Figr 6. Th pssibl d grp masss ad th prct f th spctrm i Figr 4 fr which thy acct..:l 8 m -130 Figr 8. Figr 7. -gb -59" -to 3B?~ (~) Th pssibl mmr masss fr th spctrm i

6 J Am Sc /Vlass Spctrm 1995, 6, COMPUTER NTERPRETATON OF POLYMER SPECT~A ~8 1 t 259 s i 288 t G9 88 l~ li~ 14fl 1~ z~ 118 b6~ d.~ a c l 6 8 i : zl 19 2~,.i r 2~ ~ Figr 9. Th FFT f th data i Figr 7 shw as th mdls f ach Frir trasfrm datm pit vrss th rciprcal f its abscissa. hmplymr f prpyl xid, bt hmplymr f thyl xid, ad frthrmr th cplymr was prpard by additi f th thyl xid t a prplymr f prpyl xid that rsltd i a AB blck cplymr. By applicati f th Frir trasfrm mthd t th spctrm i Figr 7, th rslt i Figr 9 is btaid. As was xpctd th pridicity f th mmr mass 58 is appart. Hwvr, thr ar svral thr aspcts that rdr this rslt f lss tility tha that btaid prvisly with crrlati mthds. Lik vry FFT algrithm, it is limitd by aliasig that rslts frm trcati (fiit mass rag) ad by th fiit mbr f trasfrm pits [18]. Mrvr, th mass distribti f th plymr is always smwhat bll-shapd istad f rctaglar. Csqtly, th Frir trasfrm f th spctrm lks lik a sris f wavs f varis amplitds ad widths that pak at masss M~ ad Mr2, which maks assigmt difficlt. Additially th thr mmr f mass 44 is barly appart as a wak pak. Althgh th Frir trasfrm mthd hr givs a lss sfl rslt tha th crrlati mthd, t gh data ar crrtly availabl t ccld that this is a gral trd. Figr 10. Th pssibl d grp masss ad th prct f th spctrm i Figr 7 fr which thy acct. By ipt f th mmr masss f 44 ad 58 prvisly dtrmid, th pssibl d grp masss ar calclatd ad shw i Figr 10. As ppsd t th plystyr cas, th mass f th d grps is t bvis. This shws th limit f th mathmatical tratmt i that cicidcs ca dmiat th rslt. Frm this ca ly ccld that th pssibl d grps cld b f at last ight vals that ca frm chmically rasabl mitis. Als th additi f r mr mmr masss t th mass f f ths d grps vals cld mak fr v mr pssibilitis. Rathr tha try t pstlat particlar d grps by sig rasabl plymr chmistry, athr apprach was tak t mathmatically rdc this rslt. Bcas th pssibl vals f d grps ar kw frm Figr 8, a rcstrcti f th plymr distribti with diffrt vals f d grps shld shw th dgr f plymrizati rqird fr ach mass-t-charg rati val i th spctrm. This shars sm similaritis with th mthd f Mtad t al. [15] t statistically prdict spctra ad match thm t th xprimtal rslt. Tabl 1 ar shw th varis dgrs f plymrizati rqird t satisfy th mass spctrm fr a varity f d grp masss btw 15 ad 33. Thr ar tw factrs basd Tabl 1. Cplymr cmpsiti cmptati fr mmrs f thyl xid ad prpyl xid" Ed grp % f EO, ~ 2 mass ma Ma Mi, Max. Ma Mi. Max , , a 1 ad 2 ar th mbr f mmr its f thyl xid (EO) ad prpyl xid, rspctivly.

7 1118 DANS AND HUBY Am Sc MassSpctrm 1995,6, lll2-111s plymr chmistry that hlp t rdc th pssibilitis. First, th prct f thyl xid, M], varis frm 8.4 t 84.5% dpdt th d grp mass sd t rcstrct th plymr distribti. Bcas th spplir stats that th thyl xid/prpyl xid mmr rati i th plymrizati is 0.15:1, th prct f thyl xid i th plymr is mst likly apprximatly 10-15%. This val f mmr rati als is dtrmid radily by tcl-miqs sch as pyrlysis gas chrmatgraphy [21] ad NMR ad ifrard spctrscpis [13]. This rslt idicats that 19 ad 33 ar likly masss fr d grps. Scd, th distribti f ~ is arrw i all cass, bt th liklihd f prdcig a distribti f ly fr mmr its is far gratr fr lw vals f 1 tha fr highr vals, which lads t frthr vidc that masss 19 ad 33 ar th mst likly vals fr th d grps f this plymr. Th 19 ca b acctd fr by trmiati f th plymr by H d, OH th thr, ad iizati by prt attachmt. Th 33 cld ccr wh a mthxy is prst istad f a hydrxy grp r cld simply b th sbstitti f prpyl xid fr a thyl xid i th plymr. This qsti cld th b rslvd with a tchiq sch as clar magtic rsac, which wld shw if thr was a xyg- r carb-bd mthyl grp i th plymr. Cclsi W hav dvlpd a prgram t aid i th itrprtati f cplymr mass spctra. Thr is a walth f ifrmati availabl i ths spctra ad it is sally difficlt fr th aalyst t xtract all th sfl ifrmati. Th prgram dtrmis th mst likly masss f th mmrs ad frm ths vals th dtrmis th mst likly masss fr th d grps. By calclatig th mmr rati ad dgr f plymrizati as a fcti f d grp mass, th d grp rslt ca b frthr simplifid. Th pssibilitis ca b rdcd gratly by th csidrig chmical ifrmati sch as lgical cmpsitis ad pssibl d grps frm kw iitiatrs ad chai trasfr agts. Oft a sigl ambigs rslt is t btaid. Hwvr, th gratst asst f this apprach is that all pssibilitis ar xamid i ctrast t th maal apprach i which th aalyst is ft satisfid wh a fit is fd, ad frthr iqiry is haltd. Ftr wrk iclds xpasi f th data bass t icld mst rasably cmm mmrs, iitia- trs, ad chai trasfr agts ad thir prdct d grps. This ifrmati will b ctaid i th tpt. Frthr rfimt f th istpic ctribti crrcti is als drway. Fially th mthd will b xtdd t plymrs that ctai mr tha tw mmrs. Ackwldgmts Th athrs ar gratfl t D. E. Karr fr hlpfl discssis ad thak Rhm ad Haas Cmpay fr spprt f this wrk. Rfrcs 1. Schlt, H. R.; Lattimr, R. P. /vlass Spctrm. Rt'i,. 1984, 3, Sait, J.; Waki, H.; Trama, N.; Taaka, S. Pr0,;r. Or q. Cat. 1988, 15, Rllis, K.; Scrivs, J. H.; Taylr, M. J.; Majr, H. Rapid Cmm. Mass Spt'clrm. 1990, 4, Mtad, G. Rapid Cmm. Mass Spctrm. 1991, 5, Ballistrri, A.; Garzz, D.; Giffrida, M.; Mtad, G.; Filippi, A.; Gaita, C.; Maarsi, P.; Pilati, F. Macrmlch's 1987, 21{), Nwaysir, L. M.; Wilkis, C. L.; Simsick, W. J., Jr. ]. Am. Sc. Mass Spt'clrm. 1990, 1, Cttr, R. J.; Hvich,. P.; Olthff, J. K.; Lattimr, R. P. Macrmlch's 1986, 19, 2Q Bltss, 1. V.; Hrcls, D. M.; valy, D.; Bighv, A. Macrmh'ch's 1987, 20, 407. q. Bl, A. M.; Ht, M. O., Jr.; DSim, J. M.; Lit, R. W. tdacrmh'ch's 1994, 27, Dais, P. O.; Karr, D. E.; Mayr, F.; Hll, A.; Wats, C. H. Or~. Mass Spc/r,.mt. 1992, 27, Bahr, U.; Dpp, A.; Karas, M.; Hillkamp, F.; Gissma, U. Aal. Chm. 1992, 4, Dais. P. O.; Karr, D. E.; Simsick, W. J.; W, D. T. Macrmh'cls 1995, 28, 122' Kig, J. L. Spctrscpy f Plymt'rs; Washigt, DC: Amrica Chmical Scity, 19cJ. 14. Adams, K.; Simsick, W. J., Jr. ]. Appl. Plym. Sci.: Appl. Phlm. Syrp. 1990, 45, Mtad, M. S.; Ballistrri, A.; Mtad, G. /Vhwrmh'ch's 1991, 24, 5{) Grgakpls, C. G.; Stathrpls, M.; Ktyaaks, J.; Parissakis, G. Cht'm. halll. Lab. Syst. 1993, 19, McLaffrty, F. W.; Staffr, D. B. ]. Chm. h{f. Cmpt. Sci. 1985, 25, 245, ad rfrcs thri. 18. Brigham, E. O. Th Fasl Frir Traslbrm ad its Applicatis; Eglwd Cliffs, NJ: Prtic-Hall, '4. Bradrp, J.; lmmrgt, E. H., Eds. Plymr HmM,k, 3rd d.; Nw Yrk: Wil.,.,, Stvs, M. P. Plym,'r Chmistry, All,trdcli, 2d d.; Nw Yrk: Oxfrd Uivrsity Prss, 199{). 21. Libma, S. A.; Lvy, E. J. Pyrl!lsis ad GC i Plymr Allalysis; Nw Yrk: Marcl Dkkr, 1984.