(& aft> J. Flow Injection Anal., Vol. 15, No. 2 (1998)

9 % ~ U - I C & ( T ~ ~ B W ^ ~ W ~ ~ - ~ W X ~ ~ > Ma^mffl

Effect of Ligand on Potentiometry and Its Application to Row-injection Analysis

Takuji KAWASHIMA, Norio TESHIMA* and Hideyuld KATSUMATA

Laboratory of Analytical Chemistry, Department of Chemistry, University of Tsukuba, Tsukuba 305-8571, Japan

The redox potential of a system involving metal ions has been modified by the complexation

of metal ions with a suitable ligand. This phenomenon has a potential capacity for the development

of novel redox systems, which are applicable to quantitative analyses. Some potentiometric

titrations of metal ions in the presence of suitable ligand are presented. Development of new types

of spectrophotometric determinations of metal ions and complexing agents is also possible by using

novel redox systems based on the ligand effect. Applications to estimation of complexing capacity

in natural water and to catalytic method for copper(I1) are also discussed. Furthermore, a new

potentiometric flow titration has been presented based on the relationship of the flow rates between

titrant and sample solutions.

'present address: Department of Applied Chemistry, Aichi Institute of Technology, Toyota 470- 0392, Japan

Fig

and (a):

0 0.5 1.0 1.5 2.0

0 2 4 0 2 4 6 [Fe(Il)l/ [V(V)l Fig. 2 Effect of zinc(I1)-EDTA ligand

PH PH buffer on the titration curves of vanadium . 1 Effect of pH on the potentials of the equimolar mixtures of iron(III) (IV) w i ~ h iron(I1) at pH 3.4. (o), none; iron(11) (0) and vanadium(V) and vanadium(1v) ( e ) (bolh 1 x l o - ' ~ ) .

cEmA = , ,0-2M; cEDTA CEDTA, 1 X IO^M; Czn, 2 X ~o^M. (b): Cphen, 1 X 1 0 2 M . = 1 X ~ O ^ M and Czndi) = 2 X 1 0 2 M .

1000

~ ~ i ~ l ~ i ~ ~ = o l o a ~ a f e t t ~ ~ . t i ~ - ~ ~ ; ~ : Ã ˆ < ~ ; t:igbT% 9, 31W b(~ l )@^fbETOSl ; !^Ki i f rLa 800

IA. -I ftu Cr(VI)/Cr(lII)Ã (I? = 1.33 V) , V(V)/V(IV)% 6m

(£ = 1.00 V) %&I$ CO(III)/CO(II)% (IT = 1.89 V) W > M 7 1 ; % 4 3 A  ¥ b $3 b i TÂ¥S 5. Z i: TO CO(III)/CO(II) 5 ^(DW@&T%%f$ L, phen ^3 2 , ~ - W 1J 3 >(bpy)

ID

( ^ l ^ - ^ - C m L k t h Z 3 , phen S/tà bpy Ul$k@T 200

T9 U A ( V I ) ~ ~ H A W ~ ^ ( V ) I Z & S 3A)b b(11)Ql@<b

s . ~ i - ? n a m ~ ~ ~ ^ , ZI w b (II)Q~@{&^M"JE <1: O o 0.5 1.0 1.5 2.0

t k. Fig. 3 ~ : ~ u A ( V I ) ~ ~ - S ; ~ A ) ~ ^ ( I I ) U ~ ~ W J S-T T. ^c~(vI) ' ' ~ 0 ~ 1 )

Fig. 3 Effect of phen on the titration curves of cobaltm with . . cfaroinium(V1) at pH 1. Concentration of phen (M): (Q), 0; (o), 2.5 x 10'"'.

i~zatm:rnÂ¥fr-r z --k. a m , 7 ~ . ( 9 ) ~ ( 1 0 ) t ( ~ ~ ~ ~ e & ~ e ~  ¥ f r ZZI: r). X/\')I/ h ( I I ) i ~ t t  ¥ 4 D A ( v I ) & B ( I I I ) W ^ W W ^ W ^ P . Tab%,

pH 1 @%fr-FT phen ??$@F2-@7fl UA(V1) i ^ ( I I I ) ~ - & % % ~ ~ , 3 IW b(11)l%@B%

S^TTS&. *Â¥rS(g)t::ZTKW@frL 9 u~(v~)$!&%fcJ;~ i , ? Cia¤ W S Y W h ( n ) % W % H r F T S k , @ ( i i i ) W K S 9 ' < % 2 i ^ ; W W t i 5 . 3fs W , ~ ^ % ~ ~ D ~ R A ~ ' ~ ~ U A < ~ ~ U I ;  £ S ~ S H $ ~ ~

-3 c~( . Iv) /c~(I I~)% @@%@<bilZlg{&M 1.61 v 2iS < , 3k-k 11 9&(1v)flSZE W c w O a ^ m ' t z ^(III)T& 9 g i J % & W ~ M , -k 1J 9 L(IV)HP&fb%E

W L - C B ~ ~ M M O . L @ L O S % , ZOIIZ'J 9&fSZ%=lA)l/ b ( I I ) ~ @ k r ^

fcJ'T5 il r?~OT"Jil^i% 5. (h il W , Co(III)/Co(II)%@ll$f?? phen @ # G T T E

TW2S ii i. W~JfflT#~tf, w^^(~v)iztb 5 -1)~:v ~ ( I I ) ~ @ < ~ % Z ^ ~ B J E T $ 3 -k .

4.1 T m f e 2 3 D ? i & % % l ~ ; b - & 5 2, B(I1) 2 l X ~ Y ~ ( I v ) ~ M I ^ f i ~ W Z c ! ~ T S S 18). Z ( S ) & ( l l ) @ S ~ ~ ~ l J f f l T S fcDT<fcSS, O T K M 4 % - T . 3, (5)fc%TCTÈW97b >@&D#GTTU, E6D7c@4~ 1 R^EZT-5:^, 1- '1 3@??1 Wft\BÇ#GS-tt i-B+Â¥h^t~_@frL -ZS(II)K%TTOH, H H D ~ > a^.n%GTTB-^fifcE^TTEJ. TOM, %7?97~4 ~&Ol%GTTW';^L (1v)D^, % ? f i n 4 >k;iL! >@@;^TTB(~~)&W':^~(iv)@gfigm,  ¥ .  ¥ ^ ^ ( D ^ W W & ^ M ^ ^ ^ ^

3.2 TZefeeb 5 I:, Fe(III)/Fe(II)%QlmTO phen D%7?TT^# L, @(111)a@{bh ^WcTS. -3, 1'1 >@%%G$-t±&(':@%D?fiB{&TL ?lZ;WW:TS. Z

h'3 2 @ D E & m % m H A ???iEjiffi b, rnfciSTC% V(V)/V(IV)O^~@ZB&$M% ~ 7 : 19.20) - $ ? % D ~ u - ~ X T ^ Z ? Fig. 4(a)l:, 77 !J>mDWi^¤ Fig. 4(b) I:%

20X 10-6 mol dm-3 [V"]

Fig. 4 Flow diagram of FIA for the simultaneous determination of vauadiumflV) and vanadium(V) a) and the

Fig. 5 Typical flow signals for the simultaneous determination of synthetic mixtures of vanadumffV) and vanadum(V).

successive merging profile of the sample solution ( V P ) + V(V)) with the iron(U,IlI), phen and dphosphale solutions b).

Wg^ V(V)^ v ( I v ) ~ ^ ~ ^ ^ T ^ % : ~ ~ ~ : ~ U -A^->£Fig 5 l ~ Z - r . -7D?%&-l^%W';^A ( ~ v ) l z f f i % T S i E e-9, W-:^A(v)fc% %TZiW -/7^^ < -5 z bAfT^-5.

Sfeil~%%?SI??F&R LT, ~ ( 1 1 1 ) / 5 ' D ~ ( V 1 ) Â £ ^ ( I I I ) / W ^ ' ^ ~ ) W I S I I ^ S ' & ~ J ~ ~ T ^ 5 21). 74- 72;b%, phen %fiTT^;(7)WEK&fTb-&&&TS% (11)-phen @@a%X@DOT@ %$%(III)DZ~ (iE fc'-9) %, -;^(4)3/tH;(8)@meIlJ >W?rFTit3@

1 1 ) >@(TI r-HA ?ik%?@is Lft. %S-f !>EÑà ["I O.OSM(pH5.6) $>mgss-rn^k^a^, 7)~-

A(III)^~^(II)% Em < (O52JS-r ¥ 2 1

LWBCDHWBEUZ. zna, a

SU M ^ f W J S . w w ( I I ) ? i i z' ^m-r-f>LE^w^^.^^, AD ^W ;btL-5 fe(OTS-5. Fig. 7 Flow diagram of r-FIA for the determination

of complexing agents.

4.4 ^MWB<orn

ng ml-l kwmla( ' Fig. 9 How diagram of H A for the determination of copper(I1). W & % o w^*B*'=?o^(n)

RT (ml min"') x CT (M) cs (MI =

Rs (rnl m i n ) (13)

Fig. 10 Row diagram of the flow titration of iron(I1) with ceriurn(1V) and of chromium(V1) with ironf11). S. sample solution; R. titrant

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(Received November 28, 1998)