CS268376B1 - Membrane for calcium ion selective electrode - Google Patents

Abstract

The essence of the solution is a membrane for a calcium ion-selective electrode formed by a foil of a suitable polymer material, for example high-molecular polyvinyl chloride with an ion exchanger based on neutral neosin, according to formula I., which are amides of 3,6-dioxaoctanedioic acid or 4-alkyl-3,6-dioxaoctanedioic acid, without distinguishing the configuration at carbon atom 4 of the acid chain, whose amide nitrogen atoms are symmetrically substituted with two cyclohexyls and two cyclohexyloxyethyls, allowing the determination of the concentration of calcium ions in a multiple excess of sodium ions.

Description

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

In practice, calcium ion-selective electrodes are widely used with a membrane formed by its own ion exchanger fixed in a matrix of a suitable polymeric material, e.g. high molecular weight polyvinyl chloride. One group of substances that form the active component of the ion exchanger are the so-called neutral carriers. Neutral supports with properties allowing wide use of this electrode in analytical practice have been described by Simon et al., Amman D., Bissig E., Giiggi M., Pretsch E., Simon W .: Helv. Chem. Acta 58, 1535 (1975). Since then, a number of acyclic and cyclic polyetherdiamides and their use in calcium ion-selective electrode membranes have been described (Czech authorship certificates No. 213 944 and No. 214 057).

With regard to the use of this electrode for the analysis of many biological materials, an important property is its selectivity for sodium ions, the activity of which is approximately one hundred times higher in most of these samples.

Such properties are exhibited by membranes for the calcium ion-selective electrode formed by a film of a suitable polymeric material, for example high molecular weight polyvinyl chloride, softened with a solution of neutral carrier and sodium tetraphenylborate in a suitable plasticizer, for example o-nitrophenyl n-octyl ether. selective for calcium ions, a substituted diamide of 3,6-dioxaoctanedioic acid or 3,6-dioxaoctanedioic acid substituted on carbon atom 4 is used without distinction of configuration on it, whose amide nitrogen atoms are symmetrically substituted by two cyclohexyls and two 2-cyclohexyloxyethyls, of schematic structural formula

wherein -R is -H, -CH 2 or -CH 2 -CH 2, such as N, N'-dicyclohexyl-Ν, Ν'-di- (2-cyclohexyloxyethyl) diamide of 3,6-dioxaoctanedioic acid, N, N'- 4-methyl-3,6-dioxaoctanedioic acid dicyclohexyl-N, N'-di- (2-cyclohexyloxyethyl) diamide and 4-ethyl- (2-cyclohexyloxyethyl) diamide 3.6 dioxaoctanedio.

Membranes with these neutral supports show a wide range of linear Nernst response to the activity of calcium ions in a mixture with sodium ions many times higher activity, good selectivity to other alkali metal ions, fast response and low drift potential.

The composition of the membranes, the response and the selective properties of the prepared calcium ion-selective electrodes are clear from the examples given.

CS 268 376 Bl

Example 1

A plastic film 0.2 mm thick, with a composition of 1.75% by weight, of a neutral carrier, in particular N, N'-dicyclohexyl-N, N'-di- (2-cyclohexyloxyethyl) diamide of 3,6-dloxaoctanedioic acid, of structural formula, was prepared.

1.01% by weight of sodium tetraphenylborate, 59.19% by weight of o-nitrophenyl n-octyl ether and 38.05% by weight of high molecular weight polyvinyl chloride (Mevil III).

The film was used as a membrane of a calcium ion-selective electrode with a reference electrolyte CaCl 2, c> 0.1 mol / l and an internal reference electrode with argent chloride. The measurements were performed at a temperature of 293 to 295 K in a cell with a reference saturated calomel electrode. The response of the electrode to the concentration of calcium ions was measured in aqueous solutions of CaCl 2, c - 10 - 10 ¹ mol / l with a constant NaCl background, c - 0.15

- 3 - _ 3 mol / l, KCl, c <5 x 10 mol / l and MgCl-, c - 10 mol / l. pH of the solutions was determined ⁴ -O -2 trishydroxymethylaminomethane c - 5 x HC1 and 10 c 4.2 x 10 mol / 1 at a value from 7.38 to 7.50. The values of the electromotive force of the cell for individual solutions are given in Table 1.

Table 1

NaCl, c - 0.15 mol / l

KCl, c - 5 x 10 ^-3 mol / l

MgCl ₂ , c = io ^-3 mol / l '.

- 2 Tris-, c = 5 x 10 mol / 1EMS

-2 HCl, c = 4.2 x 10 mol / 1 / mV /

CaCl 2, c = 10 ^-6 mol / 1-91.2 mV ^M 10 ³ mol / 1-73.4

10 ^-4 mol / 1-45.9

- 10 ^-3 mol / 1-17.2

-2 10 ^Z mol / 1 + 11.3

I0 ^-1 mol / 1 + 40.2

After t

The K _Ca J selectivity coefficients were measured by the mixed sample method, using the chlorides of the respective catheters, czo, 1 mol / l, with a constant background of tris-hydroxymethyl-2-2 aminomethane, c »5 x 10 mol / l and HCl, c« 4 , 2 x 10 mol / l in aqueous solutions, at pH 7.38 to 7.50 and a temperature of 293 to 295 K. Their values are given in Table 2.

Table 2 '

See 4 "Pot.

^K Ca, j ^*

9.3 x 10 '

CS 268 376 Bl 3

Li ⁺ Na ⁺ 2.5 χ io ' ⁴ 1.5 X 10 ⁴ K ⁺ 1.5 χ 10 ' ⁴ Rb ⁺ 3.4 x 10 ' ⁴ Cs ⁺ 9.0 χ 1O ^-5 Mg ²⁺ 1.5 χ 10 ~ ⁵ Sr ^{2 +} 7.4 x 10 ^-3 Ba ^{2 +} . 8.0 χ ΙΟ ^-3

Example 2

A plastic film 0.2 mm thick, with a composition of 1.80% by weight, of a neutral support, in particular N, N'-dicyclohexyl-N, N'-di- (2-cyclohexyloxyethyl) 4-diamide of 4-methyl-3,6, was prepared. -dioxaoctanedium, structural formula

without distinction of configuration at carbon 4 of the chain of 3,6-dioxaoctanedioic acid, substituted by alkyl CH 2, 1.01% by weight, sodium tetraphenylborate, 59.15% by weight, o-nitrophenyl-n-octyl ether and 38.04% by weight, of high molecular weight polyvinyl chloride / Melvil III /. A calcium ion selective electrode was made of the film as in Example 1, and its response to the concentration of calcium ions in the mixed solutions was measured in the same manner. The electromotive force of the cell in the individual solutions is given in Table 3.

Table 3

rlaCl, C = 0/15 mol / l KC1, C = 5 x 10 $ mol / l MgCl ₂ , c χ is ^-3 mol / l Tris-, -2 c: 5 x 10 mol / 1 EEC HCl, c = 4.2 x 10 mol / 1 / mV / -6 CaCl ₀ , c <10 mol / 1 -82.6 ² -5 - 10 mol / 1 -72.0 -4 - 10 mol / 1 -46.0 * 10 ^-3 mol / 1 -17.3 -2 ”10 mol / l +11.5 10 ^-1 mol / l +40.5 After t The selectivity coefficients K were measured as in Example 1, Ia values are listed in Table 4.

CS 268 37 «

Table i _K ^Pot ·.

Ca, j j -

NHt J 1.5 X X 10 ' ⁴ io ^-4 Na ⁺ 1.7 X io ~ ⁴ K ⁺ 1.2 X and ⁴ Rb ⁺ ·. 3, ² X 10 ' ⁴ Cs ⁺ 9.1 X and ⁵ Mg ²⁺ 1.2 X and ⁵ Sr ²⁺ 7.1 X 10 ^-3 Ba ²⁺ 3.5 X 10 ^-3

Example 3

A plastic film of thickness 0.Ϊ®ri, composition 1.83% by weight, of a neutral carrier, in particular N, N'-dicyclohexyl-.alpha.,. Beta.-di- [. 3,6-dloxaoctandel structural pattern

without distinction of configuration on the carbon atom of the 3,6-dioxaoctanedioic acid chain, substituted by alkyl -CH ₂ -CH ₃ 1.00 th »« t. sodium tetraphenylborate, 59.14% by weight of o-nitrophenyl n-octyl ether and 38.03% of high molecular weight polyvinyl chloride (Mevil III), a calcium ion-selective electrode was made of the film as in Example 1, and the response of the electrophoresis was measured. , - on the concentration of calcium ions in the mixed solutions. Electromotive values * * Salt in individual solutions are given in Table 5.

NaCl, c = 0.15 mol / l

KC1, c «5 χ ΙΟ ^-3 mol / l

MgCl 2, c - ΙΟ * ³ mol / 1 Tris-, c = 5 x 10 mol / 1 -2

HCl, c <4.2 X 10 mol / l

CaCl ,, e. iG mol / l ² -5: 0 mol / l

EHS / mV /

-88.3

-76.4

NaCl, c <0.15 mol / l KCl, c = 5 χ io ³ mol / l

MgCl 2, c = 10 ^-3 mol / l Tris-, c = 5 x 10 mol / l

CS 268 376 Bl 5 EMS HC1, c = 4.2 x 10 mol / l / mV / - CaCl-, c - ΙΟ ^-4 -3 * 10 mol / 1 mol / 1 -49.6 -21.2 - 10 ' ² mol / 1 + 7.2 • 1 10 mol / 1 + 35.4

The selectivity coefficients were measured as in Example 1. Their values are given in Table 6.

Table 6

Nlit 4 1.6 X io ^-4 -4 Li ⁺ 5.2 X 10 Na ⁺ 2.1 X 10- ⁴ K ⁺ 1.9 X io ^-4 Rb ⁺ 3.9 X 10 ^-4 Cs ⁺ 1.4 X 10 ^-4 Mg ²⁺ 4.2 X 10 ' ⁵ sr ²⁺ 1.2 X io ^-2 Ba ²⁺ 4.4 X io ^-3

Ft EDM P D ^T T INVENTION

Claims (1)

Membrane for a calcium ion selective electrode formed by a film of a suitable polymeric material, for example high molecular weight polyvinyl chloride, softened with a solution of a neutral support and sodium tetraphenylborate in a suitable plasticizer, for example o-nitrophenyl n-octyl ether, characterized in that it is used as a neutral support selective for calcium ions of a substituted 3,6-dioxaoctanedioic acid diamide substituted on carbon atom 4 without distinction of configuration on it, the amino nitrogen atoms of which are symmetrically substituted by two cyclohexyls and two 2-cyclohexyloxyethyls, of schematic structural formula Wherein -R is -II, -Cl 1 or -Cl 2 -CH 2, such as N, N * -dicyclohexyl-N, N * -dl- (2-cyclohexyloxyethyl) diamide of 3,6-dioxaoctanedioic acid, 4-methyl-3,6-dioxaoctanedioic acid N, N'-dicyclophenyl-N, N'-di- (2-cyclohexyloxyethyl) diamide and N, N'-dicyclohexyl-N, N'-di- (2-cyclohexyloxyethyl) / 4-ethyl-3,6-dloxaoctanedioic acid diamide.