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A potassium-selective silicone-rubber membrane electrode based on a neutral carrier
Analytica Chimica Acta, 64 (1973) 477--480 © Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
SHORT
477
COMMUNICATION
A potassium-selective
silicone-rubber membrane
electrode
based on a neutral carrier
J. PICK, K. TOTH and E. PUNGOR Institute for General and Analytical Chemistry , Technical University, Budapest (Hungary)
M. VASAK and W. SIMON
~
Laboratory for Organic Chemistry, Swiss Federal Institute of Technology, Zurich (Switzerland)
(Received 6th November 1972)
Electrically n e u t r a l ion-selective carriers, s u c h as c e r t a i n a n t i b i o t i c s l"s, a n d other neutral organic molecules which form complexes with alkali and alkaline e a r t h m e t a l c a t i o n s 2'4--~, a r e a t t r a c t i v e c o m p o n e n t s for m e m b r a n e electrodes o f h i g h ion selectivity 2'a, W i t h s u c h ligands, ion-selective e l e c t r o d e s of analytical significance f o r p o t a s s i u m 6-1 o, a m m o n i u m 11.12, b a r i u m I a, a n d c a l c i u m 1. i o n s h a v e been prepared. The m e m b r a n e s of these electrodes contain the ion-selective ligand in a n a d e q u a t e solvent o n s u p p o r t s s u c h as filter m e m b r a n e s 6'9'1a,14, p o r o u s c e l l u l o s e a c e t a t e 7, polyvin~¢l c h l o r i d e I s, a n d c o l l o d i o n a't 2 . B e c a u s e t h e c r o s s - l i n k e d s i l i c o n e - r u b b e r s u p p o r t s x6 h a v e b e e n very successfully used for h e t e r o g e n e o u s p r e c i p i t a t e - b a s e d ion-selective e l e c t r o d e s 17, the a i m o f t h e p r e s e n t c o n t r i b u t i o n was to s t u d y w h e t h e r electrically n e u t r a l l i g a n d s b e h a v e as carriers in s u c h inert matrices. Experimental E l e c t r o d e system. F o r t h e e.m.f, m e a s u r e m e n t s cells o f the type: Ag :AgCI,
0.01 M K C l l I m e m b r a n e l I s a m p l e s o l u t i o n l 0 . 1 M LiCI in a g a r gell0.1 M L i C I , A g : A g C 1 (1); o r A g : A g C I , 0.01 M K C l l I m e m b r a n e l l s a m p l e s o l u t i o n l 0 . 1 M 1NH41NOaKC1 (Std,), Hg2C12: H g ( 2 ) w e r e used. T h e m e m b r a n e e l e c t r o d e c o n s t r u c t i o n ( e l e c t r o d e b o d y Philips t y p e IS 560) h a s b e e n d e s c r i b e d e l s e w h e r e 6. P r e p a r a t i o n o f the membranes. T h e c h e m i c a l c o m p o s i t i o n s b y weigh t o f t h e m e m b r a n e s a r e given in T a b l e I. I n t h e case o f the P V C m e m b r a n e s (I, II) t h e s o l u t i o n o f the m e m b r a n e c o m p o n e n t s in t e t r a h y d r o f u r a n (ca. 4 ml) w a s p o u r e d into a glass r i n g (2.3 c m d i a m . ) in Contact wi.th a glass p l a t e a n d d r i e d d u r i n g t w o days at r o o m t e m p e r a t u r e (see ref. 1 8 ) . F o r t h e p r e p a r a t i o n o f t h e S R ( I I I - V ) m e m b r a n e s , t h e m i x t u r e o f the m e m b r a n e c o m p o n e n t s was p o u r e d o n a glass plate a n d p o l y m e r i z e d d u r i n g 30 :min at r o o m t e m p e r a t u r e (see ref. 16). * Although the composition of the membrane is not given in••th0se publications, there is information available that collodion and electrically neutral, carrier antibiotics were used. ....
478
SHORT
COMMUNICATION
TABLE I COMPOSITIONS
OF THE
Components
MEMBRANES
STUDIED
(wt.-~o)
Membranes
Valinomycin PVC ° SR b Diphenyi ether Dibutylsebaeate P h t h a l i c acid dibutyl ester Tetramethoxysilane Cross-linking agent c
I
11
I11
IV
V
2.5 35.0 -45.0 17.5
1.2 24.7 -. .
4.7 -•73.5 . .
3.3 -32.2
5.1 -92.0
--
74.1
17.7
--
--
---
---
-4.1
61.6 2.9
-2.9
. .
. .
° P o l y v i n y l c h l o r i d e ( S D P h o c h m o l e k u l a r , L o n z a A G , Basel, S w i t z e r l a n d ) . b Silopren KI000 (Farbenfabriken Bayer AG, Leverkusen, Germany). ¢ D i b u t y l t i n d i l a u r a t e / h e x a m e t h o x y s i l a n e (1/2 wt.).
E.m.f. measurements. All m e a s u r e m e n t s w e r e p e r f o r m e d a t 25 ° a s d e s c r i b e d e a r l i e r 6. T h e s t a n d a r d d e v i a t i o n o f a single d e t e r m i n a t i o n w a s 0.1 m V . Reagents. D o u b l e - d i s t i l l e d w a t e r ( f r o m q u a r t z ) a n d c h e m i c a l s o f t h e h i g h e s t p u r i t y a v a i l a b l e w e r e u s e d t h r o u g h o u t to p r e p a r e t h e s o l u t i o n s . T h e b u f f e r s o l u t i o n s were obtained by mixing triethanolamine and ethanolamine with acetic acid or h y d r o c h l o r i c a c i d t o a t o t a l c o n c e n t r a t i o n o f a m i n e b e l o w 0.1 iV/'.
T A B L E II RESPONSE
OF DIFFERENT
POTASSIUM-SELECTIVE
Valinomycin containing membrane (see Table I )
Millipore filter/diphenyl ether 6 PVC/diphefiyl ether, d i b u t y l s e b a c a t e (I) P V C / p h t h a l i c acid, d i b u t y l e s t e r ( I I ) SR/phthalic acid, dibutyl ester (III)
Electrode response" Range ° ( -- log ag" )
Slope° ( m V / - - log ag* )
Reproducibility (95% confidence limit) ( n l V )
Drift (AmV/time)
1~-5 5-6 1-5
59 45 57
4-0.5
< -I- 1.4 m V / 1 5 0 h
4- 2.0
+0.6 mV/24 h
1--4 4-5 1--4
55 40 55 49 54 35 59 45
4-1.0
+4.5 mV/24 h
4-0.6
+0.8 mY/24 h
4-5. SR/t.etramethoxysilane (IV) sg (V)
° A c t i v i t i e s in m o l e I - a ( M ) .
ELECTRODES
1--4 4-5 1-5 5-6
> 10 4-0.5
+ 18 m V / 2 4 h <0.1
mV/120
h~,,~,
SHORT COMMUNICATION
479
Results and discussion S o m e o f the results o b t a i n e d with cell (2) are p r e s e n t e d in Table II. T h e c h a r a c t e r i s t i c s o f t h e s i l i c o n e - r u b b e r V a l i n o m y c i n electrode (V) a r e similar to those o b s e r v e d for the filter m e m b r a n e e l e c t r o d e d e s c r i b e d earlier (~. A l t h o u g h the m e m b r a n e V c o n t a i n s c o n s i d e r a b l y less t h a n 35/0 o f solvent or s o f t e n e r (see Tables I a n d II) v a l i n o m y c i n seems to m a i n t a i n its c a r r i e r properties. In c o n t r a s t to the p r e c i p i t a t e - b a s e d silicone-rubber electrodes in which the m i n i m u m c o n c e n t r a t i o n o f p r e c i p i t a t e in the m e m b r a n e is 30 wt.-5/o, it w a s found that 5 wt.-~/o o f v a l i n o m y c i n was a d e q u a t e for the p r e p a r a t i o n o f the electrode. It is also o f interest t h a t the P V C m e m b r a n e s w i t h o u t s o f t e n e r did n o t s h o w a p o t a s s i u m i o n r e s p o n s e at all. T h e e.m.f, r e s p o n s e o f the m e m b r a n e V in cell 2 is s h o w n in Fig. 1. It is linear in the r a n g e 1 0 - 1 - 1 0 - s M w i t h a slope of 59.2 m V / - - l o g aK+ (theoretical value: 59.2). T h e stability of cell 2 ( m e m b r a n e V) w a s studied in a n a q u e o u s 10 -2 M s o l u t i o n o f p o t a s s i u m c h l o r i d e o v e r a p e r i o d o f 65 h by t a k i n g readings at time intervals o f 30 m i n (25.0 4- 0.1°). A drift s m a l l e r t h a n 0.1 mV a n d a s t a n d a r d deviation o f a single d e t e r m i n a t i o n o f 0.15 mV" were observed. The stability of the electrode p o t e n t i a l was 4-0.2 m V o v e r a p e r i o d o f 120 h in u n t h e r m o s t a t t e d conditions. W h e n the s a m p l e solutions w e r e c h a n g e d in. t h e 1 0 - 1 - 1 0 - a M KC1 range, the e.m.f. c a m e w i t h i n 0.1 m V of the final p o t e n t i a l in less than 3 s. • E x c e p t for the d i s c r i m i n a t i o n a g a i n s t h y d r o g e n (Fig. 2) a n d cesium ions, the selectivity d a t a d e t e r m i n e d a s d e s c r i b e d earlier 19 for cell (1) Showed g o o d a g r e e m e n t with values o b t a i n e d for the filter m e m b r a n e e l e c t r o d e 6 (see Table III). After 4 w e e k s o f r o u t i n e use of the electrode ( m e m b r a n e V ) i n different a q u e o u s solutions, no c h a n g e w h a t s o e v e r of t h e electrode characteristics was found. EMF
[mv]
EMF
[~v]
200 200
"Nr/' THEOR. (NERNST) ¢~
0
O- 10"1
~
_~
g )0-3
100 100
% ~ 4MK C
0
O - tO-G -100 "~KCI 0
1
2
3
4
5
6 -tog a .
-loo
- 8
;
,,
6
~
1~
1~,
Fig. 1. Response of the silicone r u b b e r m e m b r a n e e l e c t r o d e with valinomycin as ion:selective c o m p o n e n t (Cel! 2; 25°).
Fig. 2. S t e a d y - s t a t e electrode potentials in buffered K C l solutions o f the m o l a r c o n c e n t r a t i o n s indicated at different p H (Cell 2).
pH
480
SHORT COMMUNICATION
T A B L E III S E L E C T I V I T I E S KKM rot O F P O T A S S I U M E L E C T R O D E S B A S E D O N V A L I N O M Y C I N
Interfering cation M
Membrane SR membrane V
Millipore filter/ diphenyl ether ~
K + H + Li +
I 1.8. I0 -a 6.3.10 - 4
I 5.0- I0 - s 2.0- 10 - 4
NH~" Na + Rb + Cs + C a z+ Sr z +
2.3" 3.3" 1.9 3.4' 8.5' 5.4'
1.0" 10 -2 2.5.10 - 4 1.9 4.0.10 - l 2.5" 10 - 4 --
M g 2+
6.2" 10 - a
2.0- 10 -4
Ba 2+
7.2" 10 - 4
6.0" I0 - s
10 -2 10 - 4 10 -a 10 - 4 10-'~
Conclusion A new p o t a s s i u m - s e l e c t i v e s i l i c o n e - r u b b e r m e m b r a n e e l e c t r o d e b a s e d o n t h e n e u t r a l carrier v a l i n o m y c i n has b e e n d e v e l o p e d . T h e e l e c t r o d e selectivity for m o s t alkali a n d a l k a l i n e e a r t h metal c a t i o n s is c o m p a r a b l e to t h a t o f the c o n v e n t i o n a l liquid m e m b r a n e electrodes. O v e r a p e r i o d o f 65 h n o drift in e.m.f, w a s o b s e r v e d . T h e r e s p o n s e t i m e u s u a l l y is less t h a n 3 s. REFERENCES 1 Z. ~tefanae a n d W. Simon, Chim. (Aarau), 20 ( 1 9 6 6 ) 4 3 6 ; Microchem. J., 12 (1967) 125. 2 W. E. M o r f a n d W. Simon, Heir. Chim. Acta, 54 (1971) 2683. 3 (3. Eisenman, Int. Syrup. on Modern Technology in Physiologica~ Sciences, Munich, July 1971, in press. 4 C. J. Pedersen and H. K. Frensdorff, Angew. Chem., Int. Ed., 11 (1972) 16; M a r y R. T r u t e r and C. J. Pedersen, Endeavour, 30 (1971) 142. 5 R. J. Levins, Anal. Chem., 43 (1971) 1045. 6 L. A. R. Pioda, V. S t a n k o v a a n d W. Simon, Anal. Lett., 2 (1969) 665. 7 0 . K e d e m , E. Loebel and M. F u r m a n s k y , Ger. Offen. 2027128, Dec. 1970; O. Kedem, M. F u r manski, E. Loebel, S. G o r d o n a n d R. Bloch, Isr. J. Chem., 7 (1969) 87p. 8 I. H T ~ r t l l l , C. A. M a s k a n d R. E: Cosgrove, Anal. Lett., 3 (1970) 43. 9 M. S. F r a n t an d J. W. Ross, Jr., Science, 167 (1970) 987. 10 S. Lal and G. D. Christian, Anal. Lett., 3 (1970) 11. 11 R. P. Scholer an d W. Simon, Chim. (Aarau), 24 (1970) 372. 12 R. E. Cosgrove, C. A. M a s k a n d I. H. Krull, Anal. Lett., 3 (1970) 457. 13 R. J. Levins, Anal. Chem., 43 (1971) 1045; 4 4 ( 1 9 7 2 ) 1.544. 14 D. Arnmann, E. Pretsch a n d W. Simon, Anal. Lett., in press. 15 W. S i m o n and W. E. Morf, in D. Vasquez, Syrup. on Molecular Mechanisms o f Antibiotic Action on Protein Biosynthesis and Membranes, Granada, Spain, 197J, Elsevier. 16 E. P u n g o r , J. Havas, K. T 6 t h a n d G. Madar~sz, French Patent 1.402.34, 1965. 17 E. P u n g o r and K. T6th, Analyst (London), 95 (1970) 625. 18 G. J. M o o d y , R. B. O k e a n d J. D. R. Thomas, Analyst (London), 95 (1970) 910, G. J. M o o d y a n d J. D. R. Thomas, Selective Ion Sensitive Electrodes, Mer r o w , Watford, England, 1972. 19 E. P u n g o r and K. T6th, Anal. Chim. Acta, 47 (1969) 291. '
SHORT
477
COMMUNICATION
A potassium-selective
silicone-rubber membrane
electrode
based on a neutral carrier
J. PICK, K. TOTH and E. PUNGOR Institute for General and Analytical Chemistry , Technical University, Budapest (Hungary)
M. VASAK and W. SIMON
~
Laboratory for Organic Chemistry, Swiss Federal Institute of Technology, Zurich (Switzerland)
(Received 6th November 1972)
Electrically n e u t r a l ion-selective carriers, s u c h as c e r t a i n a n t i b i o t i c s l"s, a n d other neutral organic molecules which form complexes with alkali and alkaline e a r t h m e t a l c a t i o n s 2'4--~, a r e a t t r a c t i v e c o m p o n e n t s for m e m b r a n e electrodes o f h i g h ion selectivity 2'a, W i t h s u c h ligands, ion-selective e l e c t r o d e s of analytical significance f o r p o t a s s i u m 6-1 o, a m m o n i u m 11.12, b a r i u m I a, a n d c a l c i u m 1. i o n s h a v e been prepared. The m e m b r a n e s of these electrodes contain the ion-selective ligand in a n a d e q u a t e solvent o n s u p p o r t s s u c h as filter m e m b r a n e s 6'9'1a,14, p o r o u s c e l l u l o s e a c e t a t e 7, polyvin~¢l c h l o r i d e I s, a n d c o l l o d i o n a't 2 . B e c a u s e t h e c r o s s - l i n k e d s i l i c o n e - r u b b e r s u p p o r t s x6 h a v e b e e n very successfully used for h e t e r o g e n e o u s p r e c i p i t a t e - b a s e d ion-selective e l e c t r o d e s 17, the a i m o f t h e p r e s e n t c o n t r i b u t i o n was to s t u d y w h e t h e r electrically n e u t r a l l i g a n d s b e h a v e as carriers in s u c h inert matrices. Experimental E l e c t r o d e system. F o r t h e e.m.f, m e a s u r e m e n t s cells o f the type: Ag :AgCI,
0.01 M K C l l I m e m b r a n e l I s a m p l e s o l u t i o n l 0 . 1 M LiCI in a g a r gell0.1 M L i C I , A g : A g C 1 (1); o r A g : A g C I , 0.01 M K C l l I m e m b r a n e l l s a m p l e s o l u t i o n l 0 . 1 M 1NH41NOaKC1 (Std,), Hg2C12: H g ( 2 ) w e r e used. T h e m e m b r a n e e l e c t r o d e c o n s t r u c t i o n ( e l e c t r o d e b o d y Philips t y p e IS 560) h a s b e e n d e s c r i b e d e l s e w h e r e 6. P r e p a r a t i o n o f the membranes. T h e c h e m i c a l c o m p o s i t i o n s b y weigh t o f t h e m e m b r a n e s a r e given in T a b l e I. I n t h e case o f the P V C m e m b r a n e s (I, II) t h e s o l u t i o n o f the m e m b r a n e c o m p o n e n t s in t e t r a h y d r o f u r a n (ca. 4 ml) w a s p o u r e d into a glass r i n g (2.3 c m d i a m . ) in Contact wi.th a glass p l a t e a n d d r i e d d u r i n g t w o days at r o o m t e m p e r a t u r e (see ref. 1 8 ) . F o r t h e p r e p a r a t i o n o f t h e S R ( I I I - V ) m e m b r a n e s , t h e m i x t u r e o f the m e m b r a n e c o m p o n e n t s was p o u r e d o n a glass plate a n d p o l y m e r i z e d d u r i n g 30 :min at r o o m t e m p e r a t u r e (see ref. 16). * Although the composition of the membrane is not given in••th0se publications, there is information available that collodion and electrically neutral, carrier antibiotics were used. ....
478
SHORT
COMMUNICATION
TABLE I COMPOSITIONS
OF THE
Components
MEMBRANES
STUDIED
(wt.-~o)
Membranes
Valinomycin PVC ° SR b Diphenyi ether Dibutylsebaeate P h t h a l i c acid dibutyl ester Tetramethoxysilane Cross-linking agent c
I
11
I11
IV
V
2.5 35.0 -45.0 17.5
1.2 24.7 -. .
4.7 -•73.5 . .
3.3 -32.2
5.1 -92.0
--
74.1
17.7
--
--
---
---
-4.1
61.6 2.9
-2.9
. .
. .
° P o l y v i n y l c h l o r i d e ( S D P h o c h m o l e k u l a r , L o n z a A G , Basel, S w i t z e r l a n d ) . b Silopren KI000 (Farbenfabriken Bayer AG, Leverkusen, Germany). ¢ D i b u t y l t i n d i l a u r a t e / h e x a m e t h o x y s i l a n e (1/2 wt.).
E.m.f. measurements. All m e a s u r e m e n t s w e r e p e r f o r m e d a t 25 ° a s d e s c r i b e d e a r l i e r 6. T h e s t a n d a r d d e v i a t i o n o f a single d e t e r m i n a t i o n w a s 0.1 m V . Reagents. D o u b l e - d i s t i l l e d w a t e r ( f r o m q u a r t z ) a n d c h e m i c a l s o f t h e h i g h e s t p u r i t y a v a i l a b l e w e r e u s e d t h r o u g h o u t to p r e p a r e t h e s o l u t i o n s . T h e b u f f e r s o l u t i o n s were obtained by mixing triethanolamine and ethanolamine with acetic acid or h y d r o c h l o r i c a c i d t o a t o t a l c o n c e n t r a t i o n o f a m i n e b e l o w 0.1 iV/'.
T A B L E II RESPONSE
OF DIFFERENT
POTASSIUM-SELECTIVE
Valinomycin containing membrane (see Table I )
Millipore filter/diphenyl ether 6 PVC/diphefiyl ether, d i b u t y l s e b a c a t e (I) P V C / p h t h a l i c acid, d i b u t y l e s t e r ( I I ) SR/phthalic acid, dibutyl ester (III)
Electrode response" Range ° ( -- log ag" )
Slope° ( m V / - - log ag* )
Reproducibility (95% confidence limit) ( n l V )
Drift (AmV/time)
1~-5 5-6 1-5
59 45 57
4-0.5
< -I- 1.4 m V / 1 5 0 h
4- 2.0
+0.6 mV/24 h
1--4 4-5 1--4
55 40 55 49 54 35 59 45
4-1.0
+4.5 mV/24 h
4-0.6
+0.8 mY/24 h
4-5. SR/t.etramethoxysilane (IV) sg (V)
° A c t i v i t i e s in m o l e I - a ( M ) .
ELECTRODES
1--4 4-5 1-5 5-6
> 10 4-0.5
+ 18 m V / 2 4 h <0.1
mV/120
h~,,~,
SHORT COMMUNICATION
479
Results and discussion S o m e o f the results o b t a i n e d with cell (2) are p r e s e n t e d in Table II. T h e c h a r a c t e r i s t i c s o f t h e s i l i c o n e - r u b b e r V a l i n o m y c i n electrode (V) a r e similar to those o b s e r v e d for the filter m e m b r a n e e l e c t r o d e d e s c r i b e d earlier (~. A l t h o u g h the m e m b r a n e V c o n t a i n s c o n s i d e r a b l y less t h a n 35/0 o f solvent or s o f t e n e r (see Tables I a n d II) v a l i n o m y c i n seems to m a i n t a i n its c a r r i e r properties. In c o n t r a s t to the p r e c i p i t a t e - b a s e d silicone-rubber electrodes in which the m i n i m u m c o n c e n t r a t i o n o f p r e c i p i t a t e in the m e m b r a n e is 30 wt.-5/o, it w a s found that 5 wt.-~/o o f v a l i n o m y c i n was a d e q u a t e for the p r e p a r a t i o n o f the electrode. It is also o f interest t h a t the P V C m e m b r a n e s w i t h o u t s o f t e n e r did n o t s h o w a p o t a s s i u m i o n r e s p o n s e at all. T h e e.m.f, r e s p o n s e o f the m e m b r a n e V in cell 2 is s h o w n in Fig. 1. It is linear in the r a n g e 1 0 - 1 - 1 0 - s M w i t h a slope of 59.2 m V / - - l o g aK+ (theoretical value: 59.2). T h e stability of cell 2 ( m e m b r a n e V) w a s studied in a n a q u e o u s 10 -2 M s o l u t i o n o f p o t a s s i u m c h l o r i d e o v e r a p e r i o d o f 65 h by t a k i n g readings at time intervals o f 30 m i n (25.0 4- 0.1°). A drift s m a l l e r t h a n 0.1 mV a n d a s t a n d a r d deviation o f a single d e t e r m i n a t i o n o f 0.15 mV" were observed. The stability of the electrode p o t e n t i a l was 4-0.2 m V o v e r a p e r i o d o f 120 h in u n t h e r m o s t a t t e d conditions. W h e n the s a m p l e solutions w e r e c h a n g e d in. t h e 1 0 - 1 - 1 0 - a M KC1 range, the e.m.f. c a m e w i t h i n 0.1 m V of the final p o t e n t i a l in less than 3 s. • E x c e p t for the d i s c r i m i n a t i o n a g a i n s t h y d r o g e n (Fig. 2) a n d cesium ions, the selectivity d a t a d e t e r m i n e d a s d e s c r i b e d earlier 19 for cell (1) Showed g o o d a g r e e m e n t with values o b t a i n e d for the filter m e m b r a n e e l e c t r o d e 6 (see Table III). After 4 w e e k s o f r o u t i n e use of the electrode ( m e m b r a n e V ) i n different a q u e o u s solutions, no c h a n g e w h a t s o e v e r of t h e electrode characteristics was found. EMF
[mv]
EMF
[~v]
200 200
"Nr/' THEOR. (NERNST) ¢~
0
O- 10"1
~
_~
g )0-3
100 100
% ~ 4MK C
0
O - tO-G -100 "~KCI 0
1
2
3
4
5
6 -tog a .
-loo
- 8
;
,,
6
~
1~
1~,
Fig. 1. Response of the silicone r u b b e r m e m b r a n e e l e c t r o d e with valinomycin as ion:selective c o m p o n e n t (Cel! 2; 25°).
Fig. 2. S t e a d y - s t a t e electrode potentials in buffered K C l solutions o f the m o l a r c o n c e n t r a t i o n s indicated at different p H (Cell 2).
pH
480
SHORT COMMUNICATION
T A B L E III S E L E C T I V I T I E S KKM rot O F P O T A S S I U M E L E C T R O D E S B A S E D O N V A L I N O M Y C I N
Interfering cation M
Membrane SR membrane V
Millipore filter/ diphenyl ether ~
K + H + Li +
I 1.8. I0 -a 6.3.10 - 4
I 5.0- I0 - s 2.0- 10 - 4
NH~" Na + Rb + Cs + C a z+ Sr z +
2.3" 3.3" 1.9 3.4' 8.5' 5.4'
1.0" 10 -2 2.5.10 - 4 1.9 4.0.10 - l 2.5" 10 - 4 --
M g 2+
6.2" 10 - a
2.0- 10 -4
Ba 2+
7.2" 10 - 4
6.0" I0 - s
10 -2 10 - 4 10 -a 10 - 4 10-'~
Conclusion A new p o t a s s i u m - s e l e c t i v e s i l i c o n e - r u b b e r m e m b r a n e e l e c t r o d e b a s e d o n t h e n e u t r a l carrier v a l i n o m y c i n has b e e n d e v e l o p e d . T h e e l e c t r o d e selectivity for m o s t alkali a n d a l k a l i n e e a r t h metal c a t i o n s is c o m p a r a b l e to t h a t o f the c o n v e n t i o n a l liquid m e m b r a n e electrodes. O v e r a p e r i o d o f 65 h n o drift in e.m.f, w a s o b s e r v e d . T h e r e s p o n s e t i m e u s u a l l y is less t h a n 3 s. REFERENCES 1 Z. ~tefanae a n d W. Simon, Chim. (Aarau), 20 ( 1 9 6 6 ) 4 3 6 ; Microchem. J., 12 (1967) 125. 2 W. E. M o r f a n d W. Simon, Heir. Chim. Acta, 54 (1971) 2683. 3 (3. Eisenman, Int. Syrup. on Modern Technology in Physiologica~ Sciences, Munich, July 1971, in press. 4 C. J. Pedersen and H. K. Frensdorff, Angew. Chem., Int. Ed., 11 (1972) 16; M a r y R. T r u t e r and C. J. Pedersen, Endeavour, 30 (1971) 142. 5 R. J. Levins, Anal. Chem., 43 (1971) 1045. 6 L. A. R. Pioda, V. S t a n k o v a a n d W. Simon, Anal. Lett., 2 (1969) 665. 7 0 . K e d e m , E. Loebel and M. F u r m a n s k y , Ger. Offen. 2027128, Dec. 1970; O. Kedem, M. F u r manski, E. Loebel, S. G o r d o n a n d R. Bloch, Isr. J. Chem., 7 (1969) 87p. 8 I. H T ~ r t l l l , C. A. M a s k a n d R. E: Cosgrove, Anal. Lett., 3 (1970) 43. 9 M. S. F r a n t an d J. W. Ross, Jr., Science, 167 (1970) 987. 10 S. Lal and G. D. Christian, Anal. Lett., 3 (1970) 11. 11 R. P. Scholer an d W. Simon, Chim. (Aarau), 24 (1970) 372. 12 R. E. Cosgrove, C. A. M a s k a n d I. H. Krull, Anal. Lett., 3 (1970) 457. 13 R. J. Levins, Anal. Chem., 43 (1971) 1045; 4 4 ( 1 9 7 2 ) 1.544. 14 D. Arnmann, E. Pretsch a n d W. Simon, Anal. Lett., in press. 15 W. S i m o n and W. E. Morf, in D. Vasquez, Syrup. on Molecular Mechanisms o f Antibiotic Action on Protein Biosynthesis and Membranes, Granada, Spain, 197J, Elsevier. 16 E. P u n g o r , J. Havas, K. T 6 t h a n d G. Madar~sz, French Patent 1.402.34, 1965. 17 E. P u n g o r and K. T6th, Analyst (London), 95 (1970) 625. 18 G. J. M o o d y , R. B. O k e a n d J. D. R. Thomas, Analyst (London), 95 (1970) 910, G. J. M o o d y a n d J. D. R. Thomas, Selective Ion Sensitive Electrodes, Mer r o w , Watford, England, 1972. 19 E. P u n g o r and K. T6th, Anal. Chim. Acta, 47 (1969) 291. '