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Complexometric and argentometric titrations using chemiluminescent indicators
COML’LEXOME’I’KIC
AND
ARGJSN’TO_ME’I’ICIC
CHEMILUMINESCfTN’I1, Elil~lfY
TITRA’L-IONS
USING
INDICATORS
ANI> 1
r3uzAs
Wc lldvo illtTilCly clcscrilxxll~~ some new analyticd apphcntlons of the cllcmilumincscent lnchcntors slloscnc and lummol (ammophthahc nclcl hyclrazdc) which wcrc rccomnicnclcd by KlisN\- ANI> KUrcrz 3. We have shown that lophtne (z,q,s-triphcnylimlclnsolc)~~ and lucigcnm (dimethyl-cliacrycldium-dinltrxtc) G*Uarc ills0 5Ultill~lC lll
--
0
‘il N ::
0
b. III
P
I
&I N”2
NH2
1 C,,, Sri C’/N
cx
-N2
coo’-’
t t hY -0
‘coo’-’
($14 P
m
1Gg.
1.
Clicnlil~lnlincsccnt
mcchnnism
of lununol.
l 20-
In a strongly alkalme, catalyst-free media, the kinetics of the autodccompositlon of hydrogen pcrosidc are quite different. In this CZEXpcrhydrosyl ions, formed by the dissociation of hydrogen peroxide. react with the unclissoclatcd hydrogen pcrosidc molecules formIng xn unstable comples, which decomposes on collision \vith the wall of the vessel or with ;L molecule which czm tnkc up the energy. \Vc founcl tllilt lucigcnin takes up this energy from the unstable pcrhyclrosyl complex and thus csltnlyscs the decomposition of hydrogen pcroside. The trnnsfcrred energy is then emitted by the luctgcnin molecule .E, chcmilumlncsccnt light. \vlnch h;ls the snmc spcctr;~l corn--Ï position, as its fluorescent light. I-uclgcmn is rcgcncrntetl at the same tlmc. With -this clcncompositlon mcch:mism of hydrogen pcrovidr 111rcl;ltion to our previous mvcstlgatlons, wc consldcr that the chemllumltlcsccr~t mcch,mism of ito~~~col is as shown in Fig I, ‘I’hc chcmllummcsccnt reaction starts with the oulclntlon of nmlnophth:lllc ;~ltl hyclrnzldc (I) to the reel colourccl quinonc (I I). The mcsomcr pnrtncr of this clumonc, the bir~lclical (III), rcilcts with hyclrosyl or oxygen free r,?dlciLls, \\h~cll xc producctl by the oxidizing xgcnts, forming the transnnnulnr pcroxitlc* (1 V). ‘I’hls unstilhlc product loses nitrogen and emits 11ght with simultnncous spin COl~lpCll~iltiOll. ‘I’hc end-product of the rcnction IS ammophtlu~lic acid (V). ‘I’hc rciLct.loll 1s 1rrcvcrsll>lc, because mtrogcn splits off more c;lsily tlum oxygen 111the dccompositlon of the trnnsannular pcroxldc (IV). ‘l’l~ chcmilummcsccnt rcilction 1s tllus stxrtccl in the C;L\Cof lumlnol by hydroxyl or osygcn free riltlicills. With rcgnrtl to the chemllummcsccnt mech,lnlsm of I~~~g~‘nrgc,iI blue Ii&t is emitted ils ~~11 ;L%;L green lumlncsccnt light whctl n ciltillyst, P.R. ~WAV~~~rct:ll ions, 1~ present. This blue light is spectrally the \arnc as the fluorcscc*nt light of mcthykxricl~~ckly xncl tfie done, which is the osdizcd product of ldgcnin ; it clisappcw-s
‘I
I
Luclgemn
cotton
Luagenm
pcrortde
Triplet
II (11) m
Triplet Fig.
2.
Chcmilumincsccnt
Methyl
f
I
ocridonc
mcchamsm of luclgenin. Anal.
Chanr. dicta, 22 (xg60)
524-53X
526
I,.
ERDEY,
I.
13UZAS
rcztction is irrcvcrsible. Lucigenin thus emits a green hght in alkahnc media without catalysts for a long time, and the cmlttancc can be reproduced by further additions of hydrogen peroxldc; hut m the prcscnce of a catalyst the molecule splits mto two parts, ihe blue chemilumlnescent light appears :md the reaction becomes irrevcrslble. WC established by polarographic methods that lucigenin forms with hydrogen pcroxlclc a loose complex which takes up four electrons on rcductlon. We thcrcfore suggest the mechanism shown in T;lg. z for the chcmilumlnescencc of lucigenin. ‘The lucigenin catlon (I) forms luclgcnin peroxide (II) with pcrhydroxyl 10iis This molecule loses oxygen at a relatively low activation energy (20-25 621~1.) and forms an cxcltcd molecule, the hiacriclenc (III), which hns a triplet clcctron system. l’lus emits a green light by spin compcnsatlon. l‘hc blncndone (IV) is o.x.idi/.cd by a new pcrhyclroxyl ion to the luclgcnin c;ltion (I), and the cycle 1s then repeated. According to this mcchanlsm luclgcnm may bc rcgardcd as a catalyst for peroxide decomposition, transforming the energy of the reaction rnto light, while regenerating Itself. ‘L’hc fact that lucigenin emits light very c;tcadlly for a long time until the hyclrogen perosiclc is consumccl can thus IX cxpl:~incd. Water plays an important In the last reaction step. We cstablishcd that in carbon tctrachloritlc containing pyrldinc or in benzcnc, neither luclgcnln nor the biacridenc cmlts light with wntcrfree hydrogen peroxide. When water is ad&d to thcsc systems chemiluminescencc occurs immcchately. This makes it possible to detcrmmc the water content of organic solvents by ;L photometric method. In the prcscnce of catalysts an irreversible reaction also occurs. The catalyst &composes the luclgcnin peroxldc and the methylacridonc (VI) IS formed in an excited state. This emits a blue chcmiluminesccnt h&t by spin compensation. The mcthylacritlone, in the ground state, 1s icn mactivc c&ml-product. It is possihlc to use chcm~lummcscent indicators for the complcxomctric tlctcrminntion of coppcr(I1). ‘I’hc sodium salt of EIYTA stabilizes the hydrogen pcroxiclc solution, because it forms complcses with the coppcr(I1) (and other heavy metal ions) which catalyse the dccomposltion. Tn an alkaline solution containing the copper (1 I)- 13D’TR luminol shows no chcmllumincsccncc bccausc there are no hyclroxyl free racl~~.ls prcscnt. Lucigcnin however emits light steadily, bccanse it dots not require hydroxiclc free radicals for chcmilumincscc. When an ammoni;~c;~l copl)cr( II) solution 1s titrated in the prcscncc of luminol with an EDTA solution containing o.01~/~ liyclrogcn pcroxiclc, the mixture emits light until an cxccss of coppcr(I1) is present. At the ecluivalcncc pomt the light disappears. If the titration is carlicd out in the prcscncc of lucigemn, there are short fl;lshes of light before the cquiv;llcnce point IS rc4lcd but steady chcmilumincsccncc apl>ci\rs only when all the copper llns brcn titrated and hydrogen pcroxiclc no longer decomposes. pilrt
S~OL/I sOtlltlcJJJ5 o 01
i\l Chp~wr (1 I) ~u~phntc
solutmn.
z..tg6g
g
of
pro
a11nlys1
c,,so,,
* 514~0
WAS
1 of watcl Its copper content WU\ chcckcd by clcctrogravlmctlx nuaurctncnts 0 ox &I lcntl nlt.r,rtc soli~t~~~ ‘To 3 3123 g of pro anrrlysi I%(NO~)~ I 1111 (Jr z N nitric aclcl was oclckxl, and tlic mlxtutc wnr niaclc up with watci to x 1 Its lcad content \va chcclccci grnvunctrically iL9 1c;rcl s11lphatc 0 01 M inc1cuiy(I1) nltratc solrltloil I 2 g of yellow nxaxiric oxiclc was clissolvcd in 5 tnl of I 1 nitric ;rcld, irlltl tllc lnlxtrlro w;\b lli~rdc 111’ with wntcr to 1 1 ‘lb2 mercury content wab tlctcmunccl by Volhnrcl’s rnc~tliotl o I N sllvcr nitrate solutton IG 9888 g 01 pro nnalysi hgN01 was cl~usolvccl in I I of water.
clwx.~lvcrl
111
I
/17d
CkLUl.
ACfa,
22
(rgGo)
52r)-531
1ITKATIOSS
CHBMILU~Ilh’ESCENT
USISC
ISD1CAIOIZS
97
rB 60x4 6 of ICI W;LS d~sso~vctl III I 1 of water; the IoclIdc 0 I N pot.rssIum Iochdc solutiou content was Incasurcd argcntomctrically In the prewncc of \ ;LrImnInc ~illc llldlcator”. 3 8 g of h’az-EDT4 was c~Issolvccl In wstcr and I 0 g of lucigcnin x\;L~ dissolvccl with \llght lirnting ItI 200 ml ImflcufoYs I) 0 5% luclgcnlrl of water I) 0 01% lumlnol 0 I g of 1IIminol wns d~~solvccl in n nnxturc of 500 ml of wdtcr and 5 ml IJf I A’ socllum hydrowdc, :uld, after complctc dIssolutIon, the ml.\tIIrc was cldutcd to I I
Aclcl to the test solution 20 ml of 4 N ammonium 11ydrox~I~ and I ml of 0.5’11~ luclgcnin or 3 ml of o.oI~/~ of luminol solution. Heat to go”. Titrate with 0.01 111 EDTA contamIng hydrogen pcro~clc in the dark. The encl-point is indicatccl by the occurrence of a stcndy chcmilumlncsccnt light in the cast of luclgcnin or by the dlsappcarance of the light 111tlic cast of lumiiiol.
/
t1
vf
/JYP~encc
ill1
rgeJr1
5 00 0 96
20 00 50 04 _. -___ _ In
/)Ycscncc
10
.
- __.of
I7rt)ll
The rcprocluc~l~ility calculated ml
kt
from
0.x4%)
02
_
_
4-O 4 4-O 5 -t-o 13 -0 15
__-.
-
-
_
-
.._^.
-
.-_
_
NOl
5 9 20 49
-__ . _-_-
02 96 03 90
-1-o &lo -1-o --0
_ --- --
02 0 03 I.1
-..-
-i-o 4 *oo -4-o I5 -03
-
..-_
_.-
.-
of the method
ib shown in 'I‘ublcI. ‘I’llC StilllCl~lrd CIC\fl;LtlOIl~, of 0.01 :IY cupric slllpil;lte, tvcre -& 0.028 lucigcnin \v;is usc~l, ,md * 0.0.32 ml (-& o.xOrJ/o)when luminol
12 pXrilllC1
when
-t-o
+rJ 05 -t cl 01 --9 07
Of
20 01 49 97
5 00 9 96 .?o 00 so 04
. _.____-
t1
5 02
tltratlons
of 20 ml
\Vilb LlWCl.
Luminol gives an Indicator error of -+ 0 06 ml (the dat,r In ‘1’ilblC I have been corrected). It is advantageous that the dctcrmlnation can be carrlcd out cvcn in the presence of silver Ions. Strong osidizing iLgCntS and tons which form stable compleses with EDTA, naturally interfere. MZCYO-SC& deteyminat~ons. Plncc the solution contammg G-720 1~6 of copper m a s-ml titration vessel, add 1.0 ml of 4 N ammonium hydroxide ancl 0.5 ml of lurnmol indicator, heat to boiling and titrate with a suitable 0.01 or O.OOI M EDNA solution Anal. Clrsm. Ada,
22 (IgCiO)
524-531
528
I,.
I5I
I
13rmk
contalnmg Ilydrogen pcroxlclc from ;L micro burct in a dark room until chcmilumlncxcncc disappears. The accuracy of the micromcthod IS shown in Tahlc II.
73 I:! () 3’ 7 63 0
-I- 0-g -{- 0.1 -- 0 I - CJ 5
-I-15 0 -I- I 0 --
-
0
L
OH
7’1~ first procedure can lx cnrrtccl out in the rc’vwse dircctlon. ‘I’0 the: ~0. 0.01 M ICIT)‘l’A solution add 20 ml of 4 N ammonium hyclros~lc, 1 ml of 3”/, hyclrogcn pcrosicle and 3 ml of ltu-ninol or I ml of luclgcnm lndlcntor. Heilt the solution to go0 iintl tltmte tn the dark with a stanclartl coppcr(1 I) sulphatc solution. The cncl-point is indicntcd in the cabc of lucigcnin 1,~ the disnppcur;mcc of the light, with luminol IL green light appears. l’hc method, a5 is sllown by the data in ‘I‘aldc I I I, is suitable for tlic standarclixntion of ICD’I‘A solutions. ‘I’hc stnnclarcl clcw;~tions, cdculatcd from 12 pnrallcl titrations of 20 ml of 0.01 N EDTA, were * o.ozG ml (& o.I3”/J when lucigenm was used. The diffcrcncc bctwccn the mean nncl true values was -o.IO/~. With luminol thcsc dcvintions wcrc & 0.034 ml (* 0_17”/ol)and -0.2% respectively.
----_
_ __-__ 0 “I
,\I
I301 A tdc ,‘ rtd
df UWJ
1111 I~mvru oJ 3 Illrcrlrottr) ---.-_---.----_~
- _-----
5 00 9 96 20 00 50 04
of Irrcc,qr~~~u 5 01 9 93 10 93 49 93
5 00 9 96
4 96 9 97
111 prcsomz
--
20
---~
-------_-----.-
0 0, C 84SO.
00
50 0’1
--
I9
96
49.97
L,
.__--
IJJCICIICC
ml
‘xl . -_--
+o -0 -0 -0
02 03 ox
-l-o .) -0 3 -0 05
II
-0
2
-0 0‘) -1-o01
-0 8 j-0 1
-0
-0
-0
oq
07
2
-o.r,\
TITRATIOSS
L’SIXG
CIIE~IILL’.\IISI:SCl~ST
IXI~IC.\TORS
529
The titration of EDT..4 with a copper solution makes possible the detcrminntion of ions which form a stable complex with EDTA in arnmonuxal mcdta; esccss of EDT.4 can be back-titrated in the prcsencc of lumiuol or lucigcnin with a standard copper( I I) sulphnte solution.
To tbc ca. 0.01 :I[ lead or mcrcury(I1) nitrate solution add a known csccss of standard 0.01 A4 EDT.4. Heat the solution to boilmg, add 20 ml of 4 N ammonium hydrosidc, I ml of 3% hydrogen peroxide nnd finally 3 ml of luminol or I In1 of the nnxturc in the dark \\ith a stand;& coppcr(TI) lucigcnin indicator. Titrate sulphatc solution. At the cc~uivnlc~~cc~ point tlw solutton contaiuulg 1uagm111 ccasc~ to hght, wh11c in the lxcscncc of l~ml11~01 tlw dark solution lqyns to cnlit chcm1111minc~ccnce. ‘1n 13LE I \’ l>l:Tl
_
HSlI\,\TIO.S
OF
tl‘.hl>
.I, 0 I .\I
5 06 IO II 20 23
-_
30 3F
20 30 49 49
00 00 90 90
14 19 39 19
95 8.5 58 03
5 10 30 30
0s 15 32 27
-0 01 -tOOI -j-o 09 -0 07
-02
1-O *I -1-o 5 -0’ _-_-
-
Table IV shows the results of cletcrminations of lead with lucigcmn or lrm~nol indicator, while TablcV givcsmcrcury(I1) dctermmations with lumlnol. Prcclsion and accurncy data computed from 12 titrations of 20 ml of 0.01 111 solutions arc as follows. The standard deviation of the clcterminatron of lcacl was f: 0.05 ml (-+ o.z50/0) the difference between the mean and true value being -0.x %. The corresponding data for mercury(I1) dctcrminations were & 00.4 ml (& 0.21%) and-o.o50/ respectively. AIral. Chtnr. Ada,
22 (1960)
S24-53t
4.
Argentonrclr~e
dctarrninntao~~
of iodide
sons
Luclgcnin can be used as a chcmilumincsccnt of lodiclc ions. It is abSorbed m an ammomad
_-.
__0
a I A’ fake?: III!
s
Jil
I
.__
--
10 C-JO
zo 02
j0
50
0.1
01’
.--__
--
_..--
-
Ur/fcroh’ ._.._
.-_-__-
--
IONS
---‘:;,
----
__-
09
l’Ol~l:l~,N
---
ld
5 03 0 ‘1 t
00
CRCNCIS
.-
.\’
‘) 9G
IN 1I,l
_.--__
1g,\u5 II Wll ml (vrtalr of , tllrlllrom)
mdicator for argcntometric titrations media on the surface of the negative
--
-I-CJ 03
-1.0 G
---cl 02 -t 0 02
-cl 2 4-O I
+0.05 -. .-
-t-o. I
IN
I.III,
---_
TITRATION
_ .
.__.
OF
IODIIIT
Al cwcb 20 oo ml of CJI N I<1 w.a t,rkcn) _ --__ - ._ . ._. _._ --.- ._. _ -----...-_ (III
r>I h l)rfft I‘,,, rl gN0. IIT,11 ---.-_-.--_----_ ml d (wca,L.--_ uf , t1trurmrc) _-___.. _._--~-._.
t
-_--
CI-
20
03
-1.0 03
---“1, ._-__ -t- 0 15
131--
‘20
12
-to
-I
(‘N-
3” 09
-t I u OCJ
SCN-
zG.Yo
-I- 6.80
c -0 1-1
20 07
+ 0 07
-t- 0 3
Solut~c.~ncinits ligllt till I I, 10 in1 of AgNOa lb consllnlccl, but bcLOlllCS clnrk when Agt 19 prcapltntcd At the end-point at Iocd~s IIICCan I- solution when (,N- eons arc not prcscnt Llgllt tllsnppc~Lrs slowlv wl1c11 AgNO1 is ntldcd. At the cncllWl”t ;L VCry Shght hght CZLtl tJC seen Clcnr cntl-point
I’O.r-J
20
43
-(- 0 .I3
-t- 2x5
Clcnr mid-point
[I+(C N) ,I]-Q
20
GX
-I-o.GS
4
4-3 33
_1-1 GA5
hore,p, *ou
I2
#ellrctrks -.- ---
23.33
-_
Char cntl-point
00
-t- 50 5
hght is less at the m&point tlan it is when only I- ions arc prrsent No Ilgllt SIXICCl:c(CN)o-3 0x1c11ws l-10,09 A very little light appciws at tlic end-point
34
[Fc(CN),,]-.’ croq-3
- -____
And.
CjlllH
/tdU,
22
(1960)
524-53X
TITRATIOSS
USISG
CHEhIILUhlISESCENT
531
ISDICATORS
charged silver iodide precipitate and thus does not emit light cl-cn In the prcscncc of hydrogen peroxide; when the charge on the surface of the precipitate 1s changed, luclgcnm 1s desorbed and the solution suddenly lummcsces. Proccdwe
To the solution to bc cuamtncd add IO ml of 4 N ammomum hydroxlclc, I ml of IucLgemn Indicator and I ml of 0.3:/, hydrogen perosidc. ‘I’ltratc the mlxturc m a dark room until chcmllummcscent light appears suddenly and steadily.
Tables VI and VII show that the method is sultnblc for macro and micro clctcrmmatlons of iodide It is advantageous that the titration cxn bc carried out c\*cn m the prescncc of chloride and bronildc ions, the silver salts of which arc soluble in ammomum hydrouldc. When ~ganidc and to&dc mns arc prcwnt, they x-c tltratcd together. ‘I’hlocyanatcs and complc.\-forming ions intcrfcre. l’hc results of titrations carried out in the presence of other ions arc shown 111 T,~ble VIII. ‘I’hc stand,~rd deviation of the method, calculated from 12 tltratlons of 20 ml of 0.1 111 potassium iodide. was & 0.032 ml (j_- o.I~“/,) ; these was 110 difference bctwccn the mcatl and true value Chcmilurnincsccnt indicators are very useful when the solution to be csamincd is turbid, opquc or dark and the usllill dye-lncllcator5 cannot be used. I,uclycnln mcl lu~i~triol arc sultnl~lc cl~cmll~iil~incs~c~~t iadicntcm for coll~l)lcuolilctric and arfpntoinctrlc tltratkms TIM* rncch~mi~m~ of clicrnilurilllicsccncc of tlwhc indlc,ltors ill% qultc cliffcrcnt M&hods arc ~wcti for the tlctcrrn~nntlou of coppcr(lI), lcatl ;mcl fncrcury(I1) ions antI for tlic I.ucq.yim is suitable iu nn atlbolptiori incllcatoi for tlic s~nndarduatim uf 151) I‘h stAutlons of clilontlc .rnd bruimdc nrgc*ritomctrlc tlctcrmin4~twti c)f rl~llti~ wu5, cvcri in the prcwucc 11BSUXlE indhzatcurs pour Its titra~c~ coiiil~lcuoLn luci~hinc ct Ic luni~iiolc sont propos& commc mdtrqucs ct rrlCScntc]rildtrlqlIcu DCSrndttlodcsorit bt6 &Alws pour Ic rlos~gc du culvru, clu lh~nl~ La luci~hmc pcut 8trc ct du mercure ,~iu?ri quc pour I’&talonnn~c dc solutwn dc cornplcxon( III) irtllisbc comiiic intlicatcur cl’nclsc~rpt~m pour le tlosa~c m-flcntorndtriquc (1~ lodurcs. mhic cn prbscucc dc clilorurcs ct dc brcmlurcs
Luci&mm uncl T.ununol cl~ncn suzll ;rls cllclllIlumltlcscctltc Iuthkatorcn 1~1 konlplrxomctrlscllcrl Es wcrdcn I\Icttioclcu bchchrwben Lur 13cstimmuug von und argcntomctrisclicn ‘Titrationcu (I 11) LOsungcn Luciyc:nm Kupfcr, Blcl und Quccksllbcr MJWIC zur Blnstcllun~ %on l~omplcxori knnn fcrncr nls r\dsorptlonsitlrllkator IMA dcr Tltrntlon von Jotlld, WI& iti Gcgcnwart von Chlorlcl und l3romlc1, vcrwendct wcrdcn RElXRENCES ’ 1, ? 3 4 5 0 7 8
AcIn C/llW. rlcrlff Sfl I~HI>I.S, fPJd c/lO~J , 33 (1957) 459, 523: 1, I:RDr_\’ AND I UULA~, Ifgi,J&‘, 6 (1955) 93e 115. ‘“3 I_.. ERVEY, I. UUZAS AhD L I’dLOS, ,? UllUf ChCM , 109 (1959) 167. 203 1:. KENNY AND R kt, I
(1934) 3320 * L. ERDY, I. ButAs
AND
K.
VIGH, Talnntu,
I (x958)
377. nraaz. Chn.
Acfa,
22 (1960)
524-531
AND
ARGJSN’TO_ME’I’ICIC
CHEMILUMINESCfTN’I1, Elil~lfY
TITRA’L-IONS
USING
INDICATORS
ANI> 1
r3uzAs
Wc lldvo illtTilCly clcscrilxxll~~ some new analyticd apphcntlons of the cllcmilumincscent lnchcntors slloscnc and lummol (ammophthahc nclcl hyclrazdc) which wcrc rccomnicnclcd by KlisN\- ANI> KUrcrz 3. We have shown that lophtne (z,q,s-triphcnylimlclnsolc)~~ and lucigcnm (dimethyl-cliacrycldium-dinltrxtc) G*Uarc ills0 5Ultill~lC lll
--
0
‘il N ::
0
b. III
P
I
&I N”2
NH2
1 C,,, Sri C’/N
cx
-N2
coo’-’
t t hY -0
‘coo’-’
($14 P
m
1Gg.
1.
Clicnlil~lnlincsccnt
mcchnnism
of lununol.
l 20-
In a strongly alkalme, catalyst-free media, the kinetics of the autodccompositlon of hydrogen pcrosidc are quite different. In this CZEXpcrhydrosyl ions, formed by the dissociation of hydrogen peroxide. react with the unclissoclatcd hydrogen pcrosidc molecules formIng xn unstable comples, which decomposes on collision \vith the wall of the vessel or with ;L molecule which czm tnkc up the energy. \Vc founcl tllilt lucigcnin takes up this energy from the unstable pcrhyclrosyl complex and thus csltnlyscs the decomposition of hydrogen pcroside. The trnnsfcrred energy is then emitted by the luctgcnin molecule .E, chcmilumlncsccnt light. \vlnch h;ls the snmc spcctr;~l corn--Ï position, as its fluorescent light. I-uclgcmn is rcgcncrntetl at the same tlmc. With -this clcncompositlon mcch:mism of hydrogen pcrovidr 111rcl;ltion to our previous mvcstlgatlons, wc consldcr that the chemllumltlcsccr~t mcch,mism of ito~~~col is as shown in Fig I, ‘I’hc chcmllummcsccnt reaction starts with the oulclntlon of nmlnophth:lllc ;~ltl hyclrnzldc (I) to the reel colourccl quinonc (I I). The mcsomcr pnrtncr of this clumonc, the bir~lclical (III), rcilcts with hyclrosyl or oxygen free r,?dlciLls, \\h~cll xc producctl by the oxidizing xgcnts, forming the transnnnulnr pcroxitlc* (1 V). ‘I’hls unstilhlc product loses nitrogen and emits 11ght with simultnncous spin COl~lpCll~iltiOll. ‘I’hc end-product of the rcnction IS ammophtlu~lic acid (V). ‘I’hc rciLct.loll 1s 1rrcvcrsll>lc, because mtrogcn splits off more c;lsily tlum oxygen 111the dccompositlon of the trnnsannular pcroxldc (IV). ‘l’l~ chcmilummcsccnt rcilction 1s tllus stxrtccl in the C;L\Cof lumlnol by hydroxyl or osygcn free riltlicills. With rcgnrtl to the chemllummcsccnt mech,lnlsm of I~~~g~‘nrgc,iI blue Ii&t is emitted ils ~~11 ;L%;L green lumlncsccnt light whctl n ciltillyst, P.R. ~WAV~~~rct:ll ions, 1~ present. This blue light is spectrally the \arnc as the fluorcscc*nt light of mcthykxricl~~ckly xncl tfie done, which is the osdizcd product of ldgcnin ; it clisappcw-s
‘I
I
Luclgemn
cotton
Luagenm
pcrortde
Triplet
II (11) m
Triplet Fig.
2.
Chcmilumincsccnt
Methyl
f
I
ocridonc
mcchamsm of luclgenin. Anal.
Chanr. dicta, 22 (xg60)
524-53X
526
I,.
ERDEY,
I.
13UZAS
rcztction is irrcvcrsible. Lucigenin thus emits a green hght in alkahnc media without catalysts for a long time, and the cmlttancc can be reproduced by further additions of hydrogen peroxldc; hut m the prcscnce of a catalyst the molecule splits mto two parts, ihe blue chemilumlnescent light appears :md the reaction becomes irrevcrslble. WC established by polarographic methods that lucigenin forms with hydrogen pcroxlclc a loose complex which takes up four electrons on rcductlon. We thcrcfore suggest the mechanism shown in T;lg. z for the chcmilumlnescencc of lucigenin. ‘The lucigenin catlon (I) forms luclgcnin peroxide (II) with pcrhydroxyl 10iis This molecule loses oxygen at a relatively low activation energy (20-25 621~1.) and forms an cxcltcd molecule, the hiacriclenc (III), which hns a triplet clcctron system. l’lus emits a green light by spin compcnsatlon. l‘hc blncndone (IV) is o.x.idi/.cd by a new pcrhyclroxyl ion to the luclgcnin c;ltion (I), and the cycle 1s then repeated. According to this mcchanlsm luclgcnm may bc rcgardcd as a catalyst for peroxide decomposition, transforming the energy of the reaction rnto light, while regenerating Itself. ‘L’hc fact that lucigenin emits light very c;tcadlly for a long time until the hyclrogen perosiclc is consumccl can thus IX cxpl:~incd. Water plays an important In the last reaction step. We cstablishcd that in carbon tctrachloritlc containing pyrldinc or in benzcnc, neither luclgcnln nor the biacridenc cmlts light with wntcrfree hydrogen peroxide. When water is ad&d to thcsc systems chemiluminescencc occurs immcchately. This makes it possible to detcrmmc the water content of organic solvents by ;L photometric method. In the prcscnce of catalysts an irreversible reaction also occurs. The catalyst &composes the luclgcnin peroxldc and the methylacridonc (VI) IS formed in an excited state. This emits a blue chcmiluminesccnt h&t by spin compensation. The mcthylacritlone, in the ground state, 1s icn mactivc c&ml-product. It is possihlc to use chcm~lummcscent indicators for the complcxomctric tlctcrminntion of coppcr(I1). ‘I’hc sodium salt of EIYTA stabilizes the hydrogen pcroxiclc solution, because it forms complcses with the coppcr(I1) (and other heavy metal ions) which catalyse the dccomposltion. Tn an alkaline solution containing the copper (1 I)- 13D’TR luminol shows no chcmllumincsccncc bccausc there are no hyclroxyl free racl~~.ls prcscnt. Lucigcnin however emits light steadily, bccanse it dots not require hydroxiclc free radicals for chcmilumincscc. When an ammoni;~c;~l copl)cr( II) solution 1s titrated in the prcscncc of luminol with an EDTA solution containing o.01~/~ liyclrogcn pcroxiclc, the mixture emits light until an cxccss of coppcr(I1) is present. At the ecluivalcncc pomt the light disappears. If the titration is carlicd out in the prcscncc of lucigemn, there are short fl;lshes of light before the cquiv;llcnce point IS rc4lcd but steady chcmilumincsccncc apl>ci\rs only when all the copper llns brcn titrated and hydrogen pcroxiclc no longer decomposes. pilrt
S~OL/I sOtlltlcJJJ5 o 01
i\l Chp~wr (1 I) ~u~phntc
solutmn.
z..tg6g
g
of
pro
a11nlys1
c,,so,,
* 514~0
WAS
1 of watcl Its copper content WU\ chcckcd by clcctrogravlmctlx nuaurctncnts 0 ox &I lcntl nlt.r,rtc soli~t~~~ ‘To 3 3123 g of pro anrrlysi I%(NO~)~ I 1111 (Jr z N nitric aclcl was oclckxl, and tlic mlxtutc wnr niaclc up with watci to x 1 Its lcad content \va chcclccci grnvunctrically iL9 1c;rcl s11lphatc 0 01 M inc1cuiy(I1) nltratc solrltloil I 2 g of yellow nxaxiric oxiclc was clissolvcd in 5 tnl of I 1 nitric ;rcld, irlltl tllc lnlxtrlro w;\b lli~rdc 111’ with wntcr to 1 1 ‘lb2 mercury content wab tlctcmunccl by Volhnrcl’s rnc~tliotl o I N sllvcr nitrate solutton IG 9888 g 01 pro nnalysi hgN01 was cl~usolvccl in I I of water.
clwx.~lvcrl
111
I
/17d
CkLUl.
ACfa,
22
(rgGo)
52r)-531
1ITKATIOSS
CHBMILU~Ilh’ESCENT
USISC
ISD1CAIOIZS
97
rB 60x4 6 of ICI W;LS d~sso~vctl III I 1 of water; the IoclIdc 0 I N pot.rssIum Iochdc solutiou content was Incasurcd argcntomctrically In the prewncc of \ ;LrImnInc ~illc llldlcator”. 3 8 g of h’az-EDT4 was c~Issolvccl In wstcr and I 0 g of lucigcnin x\;L~ dissolvccl with \llght lirnting ItI 200 ml ImflcufoYs I) 0 5% luclgcnlrl of water I) 0 01% lumlnol 0 I g of 1IIminol wns d~~solvccl in n nnxturc of 500 ml of wdtcr and 5 ml IJf I A’ socllum hydrowdc, :uld, after complctc dIssolutIon, the ml.\tIIrc was cldutcd to I I
Aclcl to the test solution 20 ml of 4 N ammonium 11ydrox~I~ and I ml of 0.5’11~ luclgcnin or 3 ml of o.oI~/~ of luminol solution. Heat to go”. Titrate with 0.01 111 EDTA contamIng hydrogen pcro~clc in the dark. The encl-point is indicatccl by the occurrence of a stcndy chcmilumlncsccnt light in the cast of luclgcnin or by the dlsappcarance of the light 111tlic cast of lumiiiol.
/
t1
vf
/JYP~encc
ill1
rgeJr1
5 00 0 96
20 00 50 04 _. -___ _ In
/)Ycscncc
10
.
- __.of
I7rt)ll
The rcprocluc~l~ility calculated ml
kt
from
0.x4%)
02
_
_
4-O 4 4-O 5 -t-o 13 -0 15
__-.
-
-
_
-
.._^.
-
.-_
_
NOl
5 9 20 49
-__ . _-_-
02 96 03 90
-1-o &lo -1-o --0
_ --- --
02 0 03 I.1
-..-
-i-o 4 *oo -4-o I5 -03
-
..-_
_.-
.-
of the method
ib shown in 'I‘ublcI. ‘I’llC StilllCl~lrd CIC\fl;LtlOIl~, of 0.01 :IY cupric slllpil;lte, tvcre -& 0.028 lucigcnin \v;is usc~l, ,md * 0.0.32 ml (-& o.xOrJ/o)when luminol
12 pXrilllC1
when
-t-o
+rJ 05 -t cl 01 --9 07
Of
20 01 49 97
5 00 9 96 .?o 00 so 04
. _.____-
t1
5 02
tltratlons
of 20 ml
\Vilb LlWCl.
Luminol gives an Indicator error of -+ 0 06 ml (the dat,r In ‘1’ilblC I have been corrected). It is advantageous that the dctcrmlnation can be carrlcd out cvcn in the presence of silver Ions. Strong osidizing iLgCntS and tons which form stable compleses with EDTA, naturally interfere. MZCYO-SC& deteyminat~ons. Plncc the solution contammg G-720 1~6 of copper m a s-ml titration vessel, add 1.0 ml of 4 N ammonium hydroxide ancl 0.5 ml of lurnmol indicator, heat to boiling and titrate with a suitable 0.01 or O.OOI M EDNA solution Anal. Clrsm. Ada,
22 (IgCiO)
524-531
528
I,.
I5I
I
13rmk
contalnmg Ilydrogen pcroxlclc from ;L micro burct in a dark room until chcmilumlncxcncc disappears. The accuracy of the micromcthod IS shown in Tahlc II.
73 I:! () 3’ 7 63 0
-I- 0-g -{- 0.1 -- 0 I - CJ 5
-I-15 0 -I- I 0 --
-
0
L
OH
7’1~ first procedure can lx cnrrtccl out in the rc’vwse dircctlon. ‘I’0 the: ~0. 0.01 M ICIT)‘l’A solution add 20 ml of 4 N ammonium hyclros~lc, 1 ml of 3”/, hyclrogcn pcrosicle and 3 ml of ltu-ninol or I ml of luclgcnm lndlcntor. Heilt the solution to go0 iintl tltmte tn the dark with a stanclartl coppcr(1 I) sulphatc solution. The cncl-point is indicntcd in the cabc of lucigcnin 1,~ the disnppcur;mcc of the light, with luminol IL green light appears. l’hc method, a5 is sllown by the data in ‘I‘aldc I I I, is suitable for tlic standarclixntion of ICD’I‘A solutions. ‘I’hc stnnclarcl clcw;~tions, cdculatcd from 12 pnrallcl titrations of 20 ml of 0.01 N EDTA, were * o.ozG ml (& o.I3”/J when lucigenm was used. The diffcrcncc bctwccn the mean nncl true values was -o.IO/~. With luminol thcsc dcvintions wcrc & 0.034 ml (* 0_17”/ol)and -0.2% respectively.
----_
_ __-__ 0 “I
,\I
I301 A tdc ,‘ rtd
df UWJ
1111 I~mvru oJ 3 Illrcrlrottr) ---.-_---.----_~
- _-----
5 00 9 96 20 00 50 04
of Irrcc,qr~~~u 5 01 9 93 10 93 49 93
5 00 9 96
4 96 9 97
111 prcsomz
--
20
---~
-------_-----.-
0 0, C 84SO.
00
50 0’1
--
I9
96
49.97
L,
.__--
IJJCICIICC
ml
‘xl . -_--
+o -0 -0 -0
02 03 ox
-l-o .) -0 3 -0 05
II
-0
2
-0 0‘) -1-o01
-0 8 j-0 1
-0
-0
-0
oq
07
2
-o.r,\
TITRATIOSS
L’SIXG
CIIE~IILL’.\IISI:SCl~ST
IXI~IC.\TORS
529
The titration of EDT..4 with a copper solution makes possible the detcrminntion of ions which form a stable complex with EDTA in arnmonuxal mcdta; esccss of EDT.4 can be back-titrated in the prcsencc of lumiuol or lucigcnin with a standard copper( I I) sulphnte solution.
To tbc ca. 0.01 :I[ lead or mcrcury(I1) nitrate solution add a known csccss of standard 0.01 A4 EDT.4. Heat the solution to boilmg, add 20 ml of 4 N ammonium hydrosidc, I ml of 3% hydrogen peroxide nnd finally 3 ml of luminol or I In1 of the nnxturc in the dark \\ith a stand;& coppcr(TI) lucigcnin indicator. Titrate sulphatc solution. At the cc~uivnlc~~cc~ point tlw solutton contaiuulg 1uagm111 ccasc~ to hght, wh11c in the lxcscncc of l~ml11~01 tlw dark solution lqyns to cnlit chcm1111minc~ccnce. ‘1n 13LE I \’ l>l:Tl
_
HSlI\,\TIO.S
OF
tl‘.hl>
.I, 0 I .\I
5 06 IO II 20 23
-_
30 3F
20 30 49 49
00 00 90 90
14 19 39 19
95 8.5 58 03
5 10 30 30
0s 15 32 27
-0 01 -tOOI -j-o 09 -0 07
-02
1-O *I -1-o 5 -0’ _-_-
-
Table IV shows the results of cletcrminations of lead with lucigcmn or lrm~nol indicator, while TablcV givcsmcrcury(I1) dctermmations with lumlnol. Prcclsion and accurncy data computed from 12 titrations of 20 ml of 0.01 111 solutions arc as follows. The standard deviation of the clcterminatron of lcacl was f: 0.05 ml (-+ o.z50/0) the difference between the mean and true value being -0.x %. The corresponding data for mercury(I1) dctcrminations were & 00.4 ml (& 0.21%) and-o.o50/ respectively. AIral. Chtnr. Ada,
22 (1960)
S24-53t
4.
Argentonrclr~e
dctarrninntao~~
of iodide
sons
Luclgcnin can be used as a chcmilumincsccnt of lodiclc ions. It is abSorbed m an ammomad
_-.
__0
a I A’ fake?: III!
s
Jil
I
.__
--
10 C-JO
zo 02
j0
50
0.1
01’
.--__
--
_..--
-
Ur/fcroh’ ._.._
.-_-__-
--
IONS
---‘:;,
----
__-
09
l’Ol~l:l~,N
---
ld
5 03 0 ‘1 t
00
CRCNCIS
.-
.\’
‘) 9G
IN 1I,l
_.--__
1g,\u5 II Wll ml (vrtalr of , tllrlllrom)
mdicator for argcntometric titrations media on the surface of the negative
--
-I-CJ 03
-1.0 G
---cl 02 -t 0 02
-cl 2 4-O I
+0.05 -. .-
-t-o. I
IN
I.III,
---_
TITRATION
_ .
.__.
OF
IODIIIT
Al cwcb 20 oo ml of CJI N I<1 w.a t,rkcn) _ --__ - ._ . ._. _._ --.- ._. _ -----...-_ (III
r>I h l)rfft I‘,,, rl gN0. IIT,11 ---.-_-.--_----_ ml d (wca,L.--_ uf , t1trurmrc) _-___.. _._--~-._.
t
-_--
CI-
20
03
-1.0 03
---“1, ._-__ -t- 0 15
131--
‘20
12
-to
-I
(‘N-
3” 09
-t I u OCJ
SCN-
zG.Yo
-I- 6.80
c -0 1-1
20 07
+ 0 07
-t- 0 3
Solut~c.~ncinits ligllt till I I, 10 in1 of AgNOa lb consllnlccl, but bcLOlllCS clnrk when Agt 19 prcapltntcd At the end-point at Iocd~s IIICCan I- solution when (,N- eons arc not prcscnt Llgllt tllsnppc~Lrs slowlv wl1c11 AgNO1 is ntldcd. At the cncllWl”t ;L VCry Shght hght CZLtl tJC seen Clcnr cntl-point
I’O.r-J
20
43
-(- 0 .I3
-t- 2x5
Clcnr mid-point
[I+(C N) ,I]-Q
20
GX
-I-o.GS
4
4-3 33
_1-1 GA5
hore,p, *ou
I2
#ellrctrks -.- ---
23.33
-_
Char cntl-point
00
-t- 50 5
hght is less at the m&point tlan it is when only I- ions arc prrsent No Ilgllt SIXICCl:c(CN)o-3 0x1c11ws l-10,09 A very little light appciws at tlic end-point
34
[Fc(CN),,]-.’ croq-3
- -____
And.
CjlllH
/tdU,
22
(1960)
524-53X
TITRATIOSS
USISG
CHEhIILUhlISESCENT
531
ISDICATORS
charged silver iodide precipitate and thus does not emit light cl-cn In the prcscncc of hydrogen peroxide; when the charge on the surface of the precipitate 1s changed, luclgcnm 1s desorbed and the solution suddenly lummcsces. Proccdwe
To the solution to bc cuamtncd add IO ml of 4 N ammomum hydroxlclc, I ml of IucLgemn Indicator and I ml of 0.3:/, hydrogen perosidc. ‘I’ltratc the mlxturc m a dark room until chcmllummcscent light appears suddenly and steadily.
Tables VI and VII show that the method is sultnblc for macro and micro clctcrmmatlons of iodide It is advantageous that the titration cxn bc carried out c\*cn m the prescncc of chloride and bronildc ions, the silver salts of which arc soluble in ammomum hydrouldc. When ~ganidc and to&dc mns arc prcwnt, they x-c tltratcd together. ‘I’hlocyanatcs and complc.\-forming ions intcrfcre. l’hc results of titrations carried out in the presence of other ions arc shown 111 T,~ble VIII. ‘I’hc stand,~rd deviation of the method, calculated from 12 tltratlons of 20 ml of 0.1 111 potassium iodide. was & 0.032 ml (j_- o.I~“/,) ; these was 110 difference bctwccn the mcatl and true value Chcmilurnincsccnt indicators are very useful when the solution to be csamincd is turbid, opquc or dark and the usllill dye-lncllcator5 cannot be used. I,uclycnln mcl lu~i~triol arc sultnl~lc cl~cmll~iil~incs~c~~t iadicntcm for coll~l)lcuolilctric and arfpntoinctrlc tltratkms TIM* rncch~mi~m~ of clicrnilurilllicsccncc of tlwhc indlc,ltors ill% qultc cliffcrcnt M&hods arc ~wcti for the tlctcrrn~nntlou of coppcr(lI), lcatl ;mcl fncrcury(I1) ions antI for tlic I.ucq.yim is suitable iu nn atlbolptiori incllcatoi for tlic s~nndarduatim uf 151) I‘h stAutlons of clilontlc .rnd bruimdc nrgc*ritomctrlc tlctcrmin4~twti c)f rl~llti~ wu5, cvcri in the prcwucc 11BSUXlE indhzatcurs pour Its titra~c~ coiiil~lcuoLn luci~hinc ct Ic luni~iiolc sont propos& commc mdtrqucs ct rrlCScntc]rildtrlqlIcu DCSrndttlodcsorit bt6 &Alws pour Ic rlos~gc du culvru, clu lh~nl~ La luci~hmc pcut 8trc ct du mercure ,~iu?ri quc pour I’&talonnn~c dc solutwn dc cornplcxon( III) irtllisbc comiiic intlicatcur cl’nclsc~rpt~m pour le tlosa~c m-flcntorndtriquc (1~ lodurcs. mhic cn prbscucc dc clilorurcs ct dc brcmlurcs
Luci&mm uncl T.ununol cl~ncn suzll ;rls cllclllIlumltlcscctltc Iuthkatorcn 1~1 konlplrxomctrlscllcrl Es wcrdcn I\Icttioclcu bchchrwben Lur 13cstimmuug von und argcntomctrisclicn ‘Titrationcu (I 11) LOsungcn Luciyc:nm Kupfcr, Blcl und Quccksllbcr MJWIC zur Blnstcllun~ %on l~omplcxori knnn fcrncr nls r\dsorptlonsitlrllkator IMA dcr Tltrntlon von Jotlld, WI& iti Gcgcnwart von Chlorlcl und l3romlc1, vcrwendct wcrdcn RElXRENCES ’ 1, ? 3 4 5 0 7 8
AcIn C/llW. rlcrlff Sfl I~HI>I.S, fPJd c/lO~J , 33 (1957) 459, 523: 1, I:RDr_\’ AND I UULA~, Ifgi,J&‘, 6 (1955) 93e 115. ‘“3 I_.. ERVEY, I. UUZAS AhD L I’dLOS, ,? UllUf ChCM , 109 (1959) 167. 203 1:. KENNY AND R kt, I
(1934) 3320 * L. ERDY, I. ButAs
AND
K.
VIGH, Talnntu,
I (x958)
377. nraaz. Chn.
Acfa,
22 (1960)
524-531