. ..-._... _ . ..-_.. * l’t~rt Ill, see .4titrl. c:/ri,,t. .4l:fc~, AC) (l{)(\S) sfj,

SILLS has cliscussed the use of ED’I‘A to prevcrit interference-in fluorescence measurc- mcnts. Hcnv~:rc~os AXI) \VASILI;WSI;I IIRW discussed fiuorc~sc~nt titrnt$>nS+mcl M’rr.-

KISS5 has ttjscussect fluorescent indicators rctatccl to fiuorcsccin comptcx~nc;ns ha\*c ICijl~I~L AsI) Svortora”. rt would seem ttlat by choice of tllc correct per it st~ouitt IX! possible to use 8-t~ydrc~xyctuinc,1inc-g-sutfonic acid as a fiuorcsccnt indicator in titra- tions involving comptexing ilgC!ntS of ttic I5DT.4 type. ‘I‘0 carry out sucti a titration, three restricting conctitions must IX ot~S;crvcd.

(I) ‘I’lie conipicxing il#!nt uscti for titration muS;t form il mllctl strongcar c’oml~lcx than ttic conipics of ttic CiltiOlI wit11 S-tiydrosyctuinc~iint~-s-S;utfollic acid.

(2) ‘I’tic tw chosen must bc such that fiuorcsccncc* will occur. (3) ‘I’tlc conccntrntion of ttlc titrating ilgl?llt Sil0UtCi 1x2 great cIlou~t1 to CilllSL’ il com-

plete destruction of ttic* small ill?lOllIlt of ftuort!s;cing compies at tiic ctnct-point. \Vitti ttics;c restrictions in mind, il S;cGc5 of titrations wc’rc c;irric*cl out. \vitti results

shown in ‘I’ul~ttr I.

Incq+nic salt Solutions \vt’r(! tXX!t)ilrcd from rcnclgcnt gViltlc clicnii~als. A O.C~r_lO :12 sotutif)ri Of I,2-lli~llllill0~~‘~iotll!.~illli~-S,N’-tctriiilcctic ilcitl ((‘l>T;\) \v:ls

1lS;cCt ilS titrarit; IO :j :VI Sillt solutions bul! 1~Wlxircd. S-I-I~~irc~s~~ctuirioii~~c-5-Sulfc~ni~ ilcitt Soiiitif~n (0.01 ;\I) \\‘ilS t~r~t~ilN!~t l)y ctissoi~*it~~ ttll! \vl*i~lll*tt illllC~llllt of ttlr~ (:oIII-

pounci in il niinimiini of S;cdiurn t~~drc~sitic, ;lll(l ciiinting wit11 \viltC*r.

‘I’tlC (:I)‘l’:\ 1VilS C:llOS;oIl inS;tc;lcl Of EI)‘I’:\ t~C~~illlSl~ it forms more Still)iC! compit~sc5

;lh)Vc I)ti _1, ilIlt tllrb })H r:lllRcl for 1ll~lSilllUlll ill~t!IlSi~~ of ftllol’c~S;ccricx* iS t)c*t\vc*cli _# ilIICI

X for moSt coriit~tt~scs. ‘I’tI(! (YI)‘l’A \\‘ilS ohtiiinc~tt fl3~111 (;cig*.

rtl C:ilIT>*iIlg out tllc titrilticmS. IO-1111 Smlt’ics \Vt’I’C’ us~~ti* Five* tlrops of o.of f11 ,Y- Iiy~iros~cluitioiinc~-5-S~iifonic ilC:iCt wc’rl’ IlSc*tt in c*;lCll Sillllt~l~‘, i llltt ttll> Solution \\‘ilS I)Uf- fcrctt to ttic: ttcSircd prr t>> iltitlillg I0 1111 of i>uffc:r SolUt ion. Rti?ctilrcs \\‘i!I’c llliltt~’ I,>* uSing 5 ml Of CilCtl Silit solution. I<c5uitS of tllc titriitions ilrl’ Stio\vIi in ‘t’;it~ic I’. ‘t’r;lnSi- tion llletilt cittic)rlS <to not give ftuorcsccnt compicxcS.

rn consicicring ttic results rccorcioct in ‘I’ill~iC f, it hccomcs ilt~t~;lri~llt tllilt tlil! rcsuitS i\rC ctcpcncknt upon ttlc cstc?nt of conipics formation wit11 ttic! titrat inC: ilgcllt, rattlc~l than cicpendent on ttlc! formation of tllct fiuorctscent comptcx. wtlich is simply acting i1S inttic;itor.

rn CilSCS in which t)otti ions form fluorcscc!nt compicscs with ttlc incticntor, and t~~ttl form comt~icscs with ttic titriitillg ilgcIlt, ttlc results 111’0 in vt!ry gooti nq-ccmcnt. rn otlicr CilSc’S, one ion (r.g. I+) appar~ntiy is not c0riip1escc.1 I)y tllc titrating agent, wit11 the result ttiat ttic fiuorcsccncc tiisappc!~~rs wilc!n ttic fiuorcscing ion-cc,mpicx is dcstroy- ccl. Actually the Ik-OsSO:, comptcs ciocs tiavc some slight fiuorcscencc but ttlerc is il pronouncctt ctianGc at tllc voiumcs inctic~ttcd in tile ‘I’ilt>i~. rn tiic last CilSC, ttlc titrn- tion of ttlc two ions ovct-laps, t>eciluSic tilcir comptcscs arc of iLt)Ollt the same st;ibiiit>?. Hcncc tllcrc iS citllcr conlplctc illkrferencc (<‘.u--Ccl) or piirtiilt intcrfcrc.ncc. rn tlic cast of Co-%11 misturc, ttlcrc \VilS no fiuoresccnce until voiumc A was ITiLctld, ant1 ttic fluorescence ctisappcarect at volume 13. ‘ftierc? \v;is probatdy some intcrfcrcncc owing

180 JOHN A, ISISHOP

to absorption by thy’ reel cobalt solution also. ‘I’ablc I is a typical set of data and in- dicates the sprcacl of results to hc cxpectcd in cheek runs.

In ~onsi~~rixl~ thcsc results, it must he rcmembcrcd that the end-points were clc- termincd visually. Kesults reported in the previous paper on the fluurcscencc of mix- turesl slrow that by using ;L sp”ctroflur)rimcter it is possible t0 sliow fluorescence of mixtures of Cd 2nd Cu, nntl CO awl Zn, and to use this fluorcsccncc for the tletcction of the ions in the prcscnce tjf euch other.

Acid-lrast! titmtio7zs

Since, as nvtctl atxew, tiw appcaronco of fluorcsccnce takes plucc over a very short I)H ratqe, there is the pcjssibiiity that t!lt: uotnplexes might he used as &cl-base indica- tors, for titrations with end-points at the wrrcct pH. rt was ciocidotl to test this by titrating ammonia with hydrochloric i&cl solution?;. Wlicn the pkr fluoresccncc curv(:s arc consultcdl it is found that the fluorc4ng ~~~~(lxniuill complex forms uver almost the exact pH ran@ for this titration, while tlrct Mg comp1e.x is formctl at a more basic range, and the %n complex forms in a n%Jrc acidic sttlution. Freshly pWr)iIWd 0.01 M ammonin was titlXtCC1 with o,ofoo M l~yrlrt~cliloric acid, lising 3 x0-nil microburot. ‘I’cn drops of freshly prepared solutions of 0.00x &f Ccl(OxSO3)~, %n(OxSO& and Mg(OsSO;r):! were us4 as indicators. ‘lY~esc solution5 were slightly basic as origindly prcparccl, but were brought to a. f)~ of 7 before being used its intlicutors. Cllccks were run using methyl red. Rusults arcI shown in Table rr. ‘fitrations wore clonr: unclcr the mercury lamp.

AS concluclecl from the gr;kl>lls mentioned itl>ovc, the Mg complcs changed boforc the correct end-point llntl been WilCllCd xt\d tile %tI coKIlpk!X just ilftcr it, It is tltttctl, however, that the zinc cncl-point is in ~ootl aqwmcnt wlwl~ the Idank is subttactecl,

‘l’hiu investigation was supp0rtcd by Kcsctlrch Grmt X0. Hoog from the S iLtiOIW1 Institutes OC Health, Public Health Scrvicc.

.*Irrctl. Cliiwi. Aclu, 29 (1963) I7%--INI

rehctif complexant phs fort et non-fluorcsccnt. On pourrii ainsi d&clcr Ic point visa1 de titragcv comJ,icxorn~tricJL~cs ct alcnli-rrciclillibtriclucs.