CS246679B1 - Membrane for calcium ion selective electrode - Google Patents

Abstract

Membrane for a calcium ion-selective electrode, in which a wider range of linear Nernst response to the activity of calcium ions is achieved, improved selectivity for calcium ions over alkali metal ions, fast response and small potential drift, the electrode, formed by a film of plastic material, e.g. high molecular weight polyvinyl chloride, softened with a plasticizer such as o-nitrophenyl-n-alkyl ether, where 4-methyl-3,6-dioxacortic acid diamide is used as a neutral carrier, without distinguishing the configuration at carbon atom 4, whose imidic nitrogen atoms are symmetrically substituted with two phenyl and two 2-n-alkyloxyethyl, of the schematic structural formula where -R is n-alkyl -CnH2n+i, with a number of carbon atoms of 8 to 11, such as N,N'-diphenyl-N,N'- -di-(2-n-octyloxyethyl)diamide acid 4-methyl-3,6-dioxacortic acid or 4-methyl-3,6-dioxacortic acid N,N'-diphenyl-N,N'-di-(2-n-undecyloxyethyl)diamide.

Description

The invention relates to a membrane for calcium ion selective electrodes.

Various types of functional membranes are used for calcium ion-selective electrodes known and used in practice.

One group of substances applied in plastic membranes of calcium ion selective electrodes are the so-called neutral carriers, the preparation and use of which was described by Simon and his collaborators (D. Ammán, R. Bissig, M. Giiggi, E. Pretsch, W. Simon: Helv. Chim. Acta .58, 1535 /1975/). Carriers based on substituted diamides of tetramethyltriglycolic acid with an acyclic chain were also described (M. Panoch, M. Semler, O. Ryba, J. Petránek, Czechoslovak author's certificate No. 213 944).

The use of neutral supports has expanded the analytical application possibilities of the electrode by improving the selective properties. However, the methyltriglycolic acid (4-methyl-3,6-dioxacortic) derivatives described by Simon still show low selectivity towards practically important interferents.

The selectivity of a calcium ion-selective electrode with a membrane with a neutral carrier based on substituted diamides of 4-methyl-3,6-dioxacortic acid is increased by using a membrane formed by a film of plastic, such as high molecular weight polyvinyl chloride, softened with a plasticizer, such as o-nitrophenyl-n-alkyl ether, according to the invention, the essence of which lies in the fact that the neutral carrier is 4-methyl-3,6-dioxacortic acid diamine, without distinguishing the configuration at carbon atom 4, whose amide nitrogen atoms are symmetrically substituted by two phenyls and two 2-n-alkyloxyethyls, of the schematic structural formula

R

R where -R is alkyl, ^-c n ^H 2n+1' ³ P°6tem of carbon atoms n = 8 to 11, such as N,N'-diphenyl-N,N'-di-(2-n-octyloxyethyl) diamine of 4-methyl-3,6-dioxacortic acid or N,N'-diphenyl-N,N'-di-(2-n-undecyloxyethyl) diamides of 4-methyl-3,6-dioxacortic acid.

Membranes with these neutral carriers exhibit a wide range of linear Nernst response to calcium ion activity, improved selectivity for calcium ions over alkali metal ions, fast response, and small electrode potential drift.

'Example 1

Polymer membranes with a thickness of 0.2 mm were prepared in a conventional manner with a composition of 38.20 wt. percent of high molecular weight polyvinyl chloride, 59.42 wt. % of o-nitrophenyl-n-octyl ether,

0.81 wt. % sodium tetraphenylborate and 1.57 wt. % neutral carrier according to the invention, specifically N,N'-diphenyl-N,N'-di-(2-n-octyloxyethyl) diamides of 4-methyl-3,6-dioxacortic acid without resolution of the configuration at carbon atom 4, of the structural formula

, An electrode was made from the membrane with a reference solution of CaCl ₂ solution with a concentration of c = 0.1 mol/l and an internal reference silver chloride electrode. This calcium ion-selective electrode was measured in a cell with a saturated calomel electrode at a temperature of 293 °K. The following values of the electromotive force of the cell were measured in aqueous solutions of calcium chloride:

CaCl ₂ concentration cv mol/1 ΙΟ“ ⁶ 10 ^-5 10“ ⁴ 10 ^-3 10 ^-2 10 ^-1 electromotive force EMS -93.8 -74.1 -45.3 -17.1 + 8.4 +33.1 in mV For electrodes, the method was separated samples using aqueous solutions of chlorides of the respective cations with concentration c = selectivity K?°í? ¹ »3 0.1 mol/1 at temperature 293 t 1 K determined the following coefficients j -κ-Pot ^K i,3 j vPot ^K i,3 H ⁺ 2.1 X 10' ⁴ Rb ⁺ 2.4 x 10 ^-3 _NH4 2.1 x 10 ^-3 Cs ⁺ 3.1 x 10 ^-3 Li ⁺ 2.7 x 10 ^-3 Mg ²⁺ 4.7 x 10 ^-5 On ⁺ 1.3 x 10 ^-3 Sr ²⁺ 3.4 x 10" ² To ⁺ 1.3 x 10 ^-3 Ba ²⁺ 9.8 X 10 ^-3

Example2

A membrane of the same thickness was prepared with a composition of 38.53 wt. % polyvinyl chloride,

59.92 wt. % o-nitrophenyl-n-octyl ether, 0.49 wt. % sodium tetraphenylborate and 1.06 wt. percent neutral carrier, namely N,N'-diphenyl-N,N'-di-(2-n-undecyloxyethyl) 4-methyl-3,6-dioxacortic acid diamide without resolution of the configuration at carbon atom 4. As in example 1, a calcium ion-selective electrode was made and its response to the activity of calcium ions and selectivity coefficients were measured. The following values were measured:

CaCl ₂ cv mol/1 EMS in mV

10° -96.1 10' ⁵ -71.6 10- ⁴ -44.2 IO ^-3 -16.9 io ² + 8.4 10' ¹ +33.2

vzPOt ή vzPOt ^K ij ^JK i,j

H ⁺ 7.6 X 10' ⁴ Rb ⁺ 4.9 X 10' ^{3 NH4} 1.5 X 10' ³ Cs ⁺ 4.8 X 10' ³ J 2.4 X 10' ³ Mg ²⁺ 1.3 X 10 ⁴ On ⁺ 1.7 X 10' ³ Sr ²⁺ 8.4 X 10' ² To ⁺ 3.3 X 10' ³ Ba ²⁺ 8.4 X 10 ²

Example 3

The same thick membrane with a composition of 38.32 wt. % polyvinyl chloride, 59.59 wt. % o-nitro phenyl-n-dodecyl ether, 0.72 wt. % sodium tetraphenylborate and 1.37 wt. % of the same neutral carrier as in Example 1 was used to make a calcium ion selective electrode, which was measured in the same way as in Example 1 and both the response to the activity of calcium ions and the selectivity coefficients were determined. The following values were measured:

CaClj c in mol/1

EMF in mV

10'

-103.3

- 75.0

- 45.5

- 17.4 + 7.8 + 32.8 vPot ^K i,j vPot ^K i,j

H ⁺ 4.6 X 10' ⁴ NH* 1.7 X 10' ³ J 3.1 X 10' ³ On ⁺ 1.5 X 10 ³ To ⁺ 2.7 X 10' ³

Rb ⁺ 2.4 X 10~ ³ Cs ⁺ 1.1 X 10 ^-3 Mg ²⁺ 4.4 X "io" ⁵ Sr ²⁺ 3.0 X 10~ ² Ba ²⁺ 4.9 X 10 ²

Claims (1)

SUBJECT OF THE INVENTION A membrane for a calcium ion selective electrode consisting of a plastic film, such as high molecular weight polyvinyl chloride, softened with a plasticizer such as o-nitrophenyl-n-alkyl ether, characterized in that 4-methyl-3,6-dioxacorkic acid diamide is used as a neutral carrier. resolution configuration at carbon atom 4 whose amidioké nitrogens are symmetrically substituted with two phenyl groups and two 2n-alkyloxyethyly, schematic structures of whom you formula wherein R is n-alkyl ^_"CnH2n + l ^'P ° ^ ^tem carbon n = 8-11, such as N, N'-diphenyl-N, N'-di- (2-n-octyloxyethyl) 4-methyl-3,6-dioxacorkic acid diamide or N, N'-diphenyl-N, N 4-methyl-3,6-dioxacorkic acid, N-di- (2-n-undecyloxyethyl) diamide.