172 ANhl,Y’I’ICA CHIMICA ACTA

‘I’ll<: iiC:iCl itsttlf il;kS ilimt>St Ilo fhrctsccnce in tliluto W:l.tCr solutifms ;lt iIuy pH lG!- twccn 1 iLIlt 12, hit it is iwst to rtitt blanks to allow for any impurities.

f\li fiuorcsccrt~c~: xu~xeitire~n~!nt~ wcw made using tire ITarnwd Spcctrctfluorimc!tcr, the IX ,Xcnon arc lamp being uswt in ~(~sln~~ti~)n with ;t Sola ~wvcr ~~bck. “he pt~~)t~t~~~~~ WiIS tIlr: l~i~ototn~iitil~iittr tube 11’28, whicll was wnncctecl tilro~lgii iltl RCA tnicrwm- mc!tt!r trt a Variati strip recorder, type Ibro. Since tile maxima in tlw emission fre- tlucwics of tiicw complcxcs lie in the iducr-qwn rcgicni of tltc spcctrurn, :I ++o mp cut off filter ww uscti ilftcr tlie solution cuvettc.

U11fSSlwt:N 06 nnrl Pi\t<Kw i\Nr> 121C13f:sfs~7 hvc cliscnssccl ttic instrumental erwrs in- sttivcd in fluttreswncc ittt3lySiS;, In the work rcportccl hew, sinctr it was desired to study the effects of pl< change il!ltl cc~nrl~iox formation, tIlc instrument was used at constant slit wicltlt illltl ttlc ;KtiVittiCm \V:Lve lcng$l tVitP kept crawtant i&t 360 mp. iVt> correction for l~lrototubc rcslwnsc was Illi~tlC in using the fluorcsccncc intensities, since ill1 of tile

coniplcscs irivoivc:cl hat1 t~XlSinl;l ilt LLlIOUt till! SillllC! \V;LVC lcnf.$h. ‘l%e solutions wwe l~r~!~~~~r~!~l by clilutit~n of more canccntratocl solutions, wl~ich il:ltl

htrcn ma& up by mixing St~tilCtiUdizctl scrlutions of tiic inorgmic salts with frcshty

lxqmrcd standard solutions 01 tS-ilyclrctsyquinolin~-s-slrlfollic acid clissolveci in the

minimum ikfllOtlIlt of soclium l~yclroxicle requirccl for solution lwforc dilution in a volu- metric IliISlC. Inorganic salts uscti wcrc of reagent g-aclc, and the S-llyclroxycluinoiinc- 5-r;ulfonic acid was obtainccl from tiw Eastman Ktrtlak Compcm_y.

Since the osinc group itas ii hsic nitrogen, tltwe i\rC tllrcc possibic rcwting groups involved with IY-i~ytlroxycluinoline-5-suifonic acid (OxSOaH~) : OxSOd-I3+, OsSOaHn, __I-..... I . .

COMPLES FORSXATIOK ASI) FLUOHESCESCE. I =73

and OXSO~H-, all of which may dissociate. Two types of complexes arc given in the Tables of “StabilityConstants”n, ML and ML&, indicating that thcphcnolichydro~en is displaced in forming the complexes. Using the zinc compound as an example of the

-method of approach, a series of equations develops as follows:

Znz+ -t- OxSO3li3+ -> %11(OsSOa) -I- 3 i4+ (1)

(%noss(‘~:,)(l I l ):I /I” :_= . .-.- -P-P =I rr’, A-,,, l\‘,,c 11 ,,a (2)

(Zn”-+ )(oxso:ll I:,*)

%nOxS03 -t CJxSO:~l3:~’ --f %tl(OsSO:t)~~- -t, 3 I,f * (3)

(ZSl(( kxSO&“-)(f 1 *):’ I,.,’ - -- __.*_,- *...._ _ __._. _._. -,, Ii2 I\‘,,, [,*,r2 I& (4)

(%nOsS(Jg)(( JsSO:,t 13’)

‘The values for tlw constants for tlic: cornplcs&i stuclitrd in tliis p;kpc!r \Vcrt! taken from the “Stability Cttnstants”H.

The %nOxS03 is apparently ii zwittcric)n having ;L positive Cllilr&f of1 tllct zinc arid a negative charge on tlic sulfotiic jiroup.

13y iL series of approximations, tlicb iLl>t>VL! ecluution lIIik>’ IX! UMXl to tlut~~rminc tilt! distribution of tllc species in a solution containing sl.inc(II) illld OxSOnI-I:! ilt ~11~ ]>I{. Such ;L distribution is sllown in Fig. x. I *tnd leas lJcc*n CillCUlittWl for tilt! otllt*r ions dis- cussed in tliis paper.

In Fig. I. there is also &own the variation c3f fluorosccncc intensity with pri, 4 solutions containing zino(If) and OxSO3H2, referred trt the ~nii?cilllUnl intensity of flu- orescence of the zinc complcs (ilt I>H 6). ~Itl,IASlS his usctl tllis type of plot to ShOW

that thcrc are two fluorescing spccics in tlic cusc of anthr;milic acicl’~. In tlic prcscnt: case, it cnn be s;ccn b+v inspection of Figs. x iIntl 2 tllat tile fluorescence is entirely clue to the scconcl complex.

In Fig, 2, there is shown the variation of fortli~Ltiott of tllc scconrl comlks with OXSO32” With pH for Cd, %n :Lncl ikfg itl<)ng with the Vari;lth of fluoresccncc intensity of the snmc solutions with PH. M~cDouc~~t~. J has investigated tlie clwqc in fluorcs- censc intensity of tlw Mg complux with PH. Iic rqwrts that it incrcascs to CL maximum

174 JOHS A. HISHOP

nncl then decrcuscs, probal,ly owing to the formation cithcrof hytlroxycomplcxes or of the hyChJXick. ‘I’hc present writer has ccJnfirmcd this effect with the magnesium complexes, and has found a similar clccrease in fluorcsccncc intensity at high pH values for the %x-i and Ccl complexes. Wie complexes of the last two are stable at lower pH V;llUCS, ~l(JW!Ver, as can bc seen from Fig. 2, and hcncc !lavc ;t much wicicr pH range O\‘(!l- WhiC~l tllc) can 1~ used, than the magnesium complex.

PH Zn Cd

I’rtJIll thcl ~lll~l~ytic;l~ St~lll<~~XJint, SdUtiOW COllt~hillg <)X%hI~:! Il:lVC! tllc! ;dV~lIlt~l@!

that the solutions used (cation antI O.xSO:,Ha) ~l;lvc 110 f~Uorcsccncc c~f th!ir own. It iS

possible, tlic:rcforc, to use graphs of the type shown (Figs. I ant1 2) to choose conditions for an analysis involving ttic mcasuremcnt of fluorcsccnce intensity. It is true that tlris intensity is ;lffcctctl somewhat by c’xccss OxSOnH:! (Fig. 3), hut tllis c;m 1~ allow- et1 for hy using il standard amount of tllc cotnplexiiig agent greatly in cscc’ss of tllat nccdctl for formation of tlie complex. Al, Ikk, Sr, (:a, NC, Cu, Xi, Co ions havcalso hccn tc!strd for fluorcsccnco in solutions of OSSO:,HZ. Results for thcsc* cations follow tllc rc-

C0JfPtE.S FORbfATION Ah’D FLUORESCENCE. I I75

suits of STEVESS”, who found that complexes formed by 8-quinolinol dicl not fluoresce when the cation involved was one of the transition metal ions.

In using these graphs for analytical work, there a.re two sets of conditions that mav be chosen. ‘The first is to select a PN such that one cation complex fluoresces and on19 one. This is relatively simple when the cations involved include only ffnc that forms a fluorescent complex. Combinations of this type arc shown in Fig. 4. in which IL xo- fold excess of the complcxing ligand was used, dong with it pH such that the comIdex was all in the MI,:, form.

If more tlkan one cation forms a fluctrc?;wnt cwnlpkx, it is p~~ssihlc to set conditions such that only one of thctsc will fluoresce. Thus, Fig. 2 indicntc5 tllilt it shoufcl hc I>f>s- siblc to dcdcrminc zinc in tlic prcsencc: of magnesium at it pn of 4.5. It is true, liowcver, tllat ilrl iIlcIX%Sc in cation cc~IlWIltri~tion Wili mo\V tilt! cuI’\‘cI tow%rdS il lower pH, ;lncl

Cd

Mg

therefore, an increase in tlw MXJUnt of magnesium accompanied by a decrcasc in the

amount of zinc could C;LUSC’ overhpping ant1 prevent tlic determination. It is evident,

ncvcrtIwIez++, that. it is possil,le to set contlitif3ns for such ~oml~in~ti~3ns in which the cation present in much smaller amount 1~s tlw I(3wcr stuhility constant for its complex.

Thus the effect of traces could bc avt3idotl.

J3y setting conclitions such that both wtir3n eomplcxos will fluoresce at maximum

intensity, it iS pcJSSil?h! t(J &*tf:rfnhe f>fJth WthJw, pr(Jvidh&$ tht the two fhmrescemx

intcnsitics art! ;ultliti\*t:. This ~urnniati~m of fluoresccncc irltensity is and_qous to the

act~litivity c3f S;ctlutic)n clctnsitiw in ~;i,ctctrr~~3l;otttmctry. *Just :IS the additivity of al~~3r-

I~tnceS is p(3SSil3ie (31ily if I3rttll col0rctI sul3Strtnccs follow IG52-‘S law, tlw additivity of

fluorc:sccncc intensities is prwil3lc only if the SftllltbJnS iLrC of sucli tt3w concttntratic3n

tIMi. fIuOrCSCL’ilC:C! iilt<!?lsit~ iS i3rO~3{Jrti(311~~1 to ~~Jil~~litr~itiO~~. 111 tk c;LsC,

/:A .I- I:,, L: /I,\C,, -I- /tr,Cr,.

Scmw r:c~tnl~in;~tit)iis cbf tltis type arc ~liot~t~ in l;ig. 5, a)nditit>ns Iwing in(lic;ttc(l on

tlw grapli.

‘I’lle rnctllr3cl WcCt in wttirig 1113 tilt: firii)>‘ilS C)f ITi&+ 4 Mltl 5 rl1ily IX! wmmarizcci IlS

fc~Il0ti?i, to ltilitl?‘%L’ for t\%‘\‘cJ ions A Mid IS.

I.)ilutc tile sa~nple to c!xi\ctly IOO ml (or any convcnitrnt volunw). ‘I’c\kc a11 alicluot

portir3n and ~u~tly~c ftlf Itr3tIl iOIlS (AZ A t IS>. ‘II& rn;iy 13~ clortc by ttnv mettit3d wltich

will clctcrmitw botll, but an 151Yl’A titratic3n Stems Iwst for most cations. ‘I’akc a Siccund

alicjuot for tlilution to x0-’ 6 or IO..@ AZ in il XOO-ml volumetric flask. 7’0 tltis sample in

tlir: vt~lutttctric fliLSk ;\&I ;l &finite VOIUllW of OSSO3Hz SOIUtiOI1 (O.Ot &I i\rlCt nt the p,tf

to ix2 usctl), wi&Al will 13~ in lzirgc cxwss over what is twetic<l to complex lwtli ions.

A&l bulfcr of tllc tlcsircd 13” (solution I), Prcparc II solution of ir3n A of the niolarity

tisccl in suluticm L for tftc Sum of tlte twt3 ic3nS,itlcluclin~in tlio solution tlll!SiWlo~tmOu~t

trf OxSO3I-I:! and tfic saw iLm(3Ut1t of buffer $6 in sc3lution I (St3lutiun 2). Prcpnrc a

SittliliW sultttioti for ion 13 (solution 3). Ol>tain fluorcscencc intensity curves for the solu-

tions I, 2 wtd 3. L;ilL;llly calculate ttW amoutlt of tlw ion prcscnt, iLSStlt?litl~ that ion A

COltll31CS IIUS ;L IoWC~ fluorcsccncc ilt tllc p,!~ll~ tlliltl 13.

i-“,lx ‘.. I.-,\ ~lilli~lXllls elf It --= .I’- --.-‘....I’--.. . ‘. (ill,\, 1~) (Atomic \vt. :\) (1111 Of ctri~illi\l Si~IillTlL+)

1: ,, ‘-I I;*

fl tltc hhtlc is iC4Stl~lll!tl to Iw tlto Same for all sctlutiont;, it t?liky ix ignowci since only

tliffcronccs i11’c‘ llSl!tl. Ill CilSCS il1 which OIIC Of the t\vO iotw tlOcS not CiItlSC fluorcsccnco

(Siucli r&S copper), tllc ViLitlC obtainctf with SUCll il solutit3n tnay t>c cwsiderrrcl to l3c till.!

I>lilllk.

If it is tft!sirctl to prqiwe i\ &YLl’lk to IX.! IlSWi i1S iI 1~~rllli~~lC~~lt refcrcnce, tlW fluctrcs- ci:nCc Wlily 1x2 rcfcrrctl tu some rq~rocluciblc StilllCIWtl, such as rluinitw Sulfatu,

‘i’ltis itivcstig;ttiott was supportcci by research grant So. X005 from the Xational

Iiwtitutc C)C Hk!illtll, I’uMic I-llJi\ltll Swvicc.

COMPLES FORMATIOK ASD I’LUORESCESCE. I 177

L’autcur a fait unc’ L(tuiIc sur la fluoresccncc dcs solutions tic co~ilplcxcs tic cations avc’c lo sulfo- 5-l1~tlrox~-Y-quiii~l~ixl~. I.cs complcxcs form& nvcc Its dltiincnts tic transition nc fluorcsccnt pas. I.‘influcncc tlti pfr n tltd cxainin& ct pcriiict d’cnvisagcr 1111~ nouvclle mc!thodc nnnlytiquc appli- cubic h rlcs nlr’lnngw dc c;ltions nvnnt tics rhctions simihircs. <‘c procdtl& convicnt qdcialcincnt pour & f;tilJlcs clunntitL:s tl’&zhaniillon 011 Imtir tics hhmtillons trcs tlilu&.

I)ic I~luorcszcns clcr I.i)sunjicn van I~;ltic,iicii-ll;oili~)lc?tcn mit H-1 I~tlro~~cllilloliil-J-sulfosiiltrc. wurtlc untcrsucht. iicmi~~lcsc, clic iiiit tlcn t!l)crR;inffsclciiicnlcri f+2l)ililct wcrclcn, fluorcszicrcn nicht. I)ic AclcIiti\*itiit dcr I-Iuorcszi~nz twi Iwstiirirntcn piI-\Ycrtcn wurtlc* fiireirw ncuc. ;tn;ilytisclic Mcthodc 1x.nutir.t. Sic ist tlnnn ;lIIgciiicin anwcncllxlr. \vcnn .\lischungcri vc,n Kiltioncii mit iihn- licllcn Rcaktioncn vorlicgcn. I>ic .\lcthotl~* cignct sicll ~Jlwjntlcrs fiir klcinc~ otlcr schr vvrcliinntc I%-c~lwn.