CS244648B1 - Calcium ion selective electrode membrane - Google Patents

Abstract

A membrane for a calcium ion-selective electrode exhibiting a wide range of linear Nernst response to the activity of calcium ions, high selectivity for calcium ions, especially towards alkali metal ions, small electrode potential drift and fast response, consisting of a film of plastic, such as polyvinyl chloride, plasticized with a plasticizer, preferably o-nitrophenyl-n-alkyl ether, where the advantage is achieved by using a neutral support, formed by 3,6-dioxacortic acid diamide, the amidic nitrogen atoms of which are substituted symmetrically by two phenols and two 2-n-alkyloxyethyls, of the schematic structural formula where -R is alkyl CnH2n+1 with the number of carbon atoms n = 8 to 11.

Description

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

Various types of functional membranes are used for the known calcium ion selective electrodes. Crystalline calcium tungstate (J. Vesely, J. Jindra, c., Pat. No. 163 358) or mixed calcium fluoride with lanthanum fluoride (C.H. Parren, Germany Patent No. 2 101 339) may be used for splide-type membranes.

In polymeric polyvinyl chloride membranes, the first of the active materials was calcium di-n-alkyl phosphate (J.W. Ross Jr., Science 156. 1378 (1967)). Calcium salts of diarylphosphoric acids such as calcium di- (4-n-octylphenyl) -phosphate (CJ Tjell, J. Ruzicka, DOS 2,349,299) and calcium di- (4-tert-octylphenyl) -phosphate (RE) are also known. Cosgrove, U.S. Pat. No. 3,721,401 '.

The monocrystalline sensors made of inorganic materials have not been widely distributed for non-ideal responses and low selectivity. The active materials based on calcium salts of diesters of phosphoric acid show a good electrode response to the activity of calcium ions, but their analytical utilization is complicated by their low selectivity especially towards H 2 O and Mg ions.

Other materials for calcium ion selective electrode membranes are the so-called neutral carriers, first described by Simon and co-workers (D. Amman, R. Bissig,

M. Guggi, E. Pretsch, W. Simon: Helv. Chim. Acta 58, 1535 (1975)). Neutral supports based on substituted tetramethylglyconic acid diamides with acyclic chain have also been described (M. Panoch, M. Semler, 0. Ryba, J. Petránek, US Patent No. 214,057) and cyclic polyetherdiamine (J. Petránek, 0). Ryba, M. Semler, M. Panoch, Czech author's certificate No. 213 944).

The use of these materials has expanded the analytical application of the electrode by improving the selective properties, but nevertheless the Simon-substituted triglycolic (3,6-dioxacorkic) derivatives described by Simon exhibit low selectivity to virtually important interphenents.

To increase the selectivity of the calcium ion selective electrode with a membrane with a neutral 3,6-dioxacorkic acid carrier, the neutral carrier of the present invention consists of a substituted 3,6-dioxacorkic diamide, which is characterized in that the nitrogen nitrogen atoms are symmetrically substituted two phenyls and two 2-n-alkyloxyethyls, represented by the general structural formula.

wherein -R are n-alkyls having a carbon number of 8 to 11 °

Membranes with these neutral carriers exhibit a wide range of linear Nernst responses to calcium ion activity, high selectivity for calcium ions, especially to alkali metal ions, low drift potential of the electrode, and rapid response.

Example 1

A polymer membrane of 0.2 mm thickness of 38.63 wt. % high molecular weight polyvinyl chloride, 60.08 wt. % o-nitrophenyl-n-octyl ether, 0.45 wt. % sodium tetrafenylborate and 0.84 wt. % of the neutral carrier according to the invention, namely N, N'-diphenyl-N, N-di (2-n-octyloxyethyl) 3,6-dioxacorkic diamide, structural formula c

An electrode with a reference electrolyte of CaCl ₂ at a concentration of c = 0.1 mol / l and an internal reference argentichloride electrode was made from the membrane. The electrode was measured in a cell and a saturated calomel electrode at a temperature of 293 K. The following values of the cell's electromotive force were measured in aqueous calcium chloride solutions:

c [mol / lj electromotive force [mV]

10 ^-6 - 100.9 , 0-5 - 75.4 10 ^-4 - 46.3 10 “ ³ - Π.5 10 ² + 8.6 10 “ ¹ + 32.9

For the electrode, the following selectivity coefficients were determined by the separate sample method for the use of aqueous chloride solutions of the respective cation ions, at c “0.1 mol / l and a temperature of 293 K:

3 «Pot ^K i, d j «Pot ^K i, OJ ^C ,, p Mg ² * 3.1 χ 10 ⁵ On* 1.2 χ 10 ' ³ Sr ² * .1.7 x 10 ' ¹ TO* 2.1 χ 10 ^-3 Ba ² * 3.8 x 10 ~ ¹ Rb * 2.6 χ, 0 ^-3 If* 9.6 χ 10 ^-4 Cs * 2.8 χ 10 ^-3

Example 2

An equally thick membrane of 38.53 wt. % polyvinyl chloride, 59.93 wt. % o-nitrophenyl-n-octyl ether, 0.46 wt. % sodium tetrafluoroborate and 1.08 wt. % of the neutral support, namely N, N'-diphenyl-N, N'-di (2-n-undecyloxyethyl) 3,6-dioxacorkic diamide, was used for the ion-selective electrode as in Example 1 and for aqueous calcium chloride solutions showed the following values of the electromotive force of the cell:

£ mol / l) electromotive 10 ⁶ - 105,0 10 ' ⁵ - 76.4 10 ^-4 - 47,3 10 ^-3 - 18,2 10 ^-2 + 8,9 10 “ ¹ + 33.5

The selectivity coefficients measured as in Example 1 showed the following values:

3 «Pot ^K i, j j «CS Mg ² * 3.1 x 10-5 On* 7.8 x IO ' Sr ² * 2.9 x 10 " TO* 3.3 x 10 “ Ba ² * 1.4 Rb * 5.4 x, 0 v. + If 1.1 χ 10 ^-3 Cs * 5.2 x IO

Example 3

An equally thick membrane of 38.41 wt. % polyvinyl chloride, 59.75 wt. % o-nitrophenyl-n-dodecyl ether, 0.57 wt. % sodium tetrafluoroborate and 1.27 wt. 56 of a neutral support, namely N, N'-diphenyl-N, N'-di (2-n-undecyloxyethyl) 3,6-dioxacorkic diamide, was used to produce a calcium ion selective electrode similar to Example 1 and was as in Example 1. Example 1 measured and determined coefficients of selectivity) The measured values showed the following results:

c Jmol / -6J -6, 0 '

10 'it

Mg '

Sr

Ba

L?

2+

2+

2+ yPOtr

6.2 x, 0-5 3.6 χ ΙΟ ¹ 4.1

2.0 χ, 0 “ ³

On

Rb

Cs * electromotive force τ (mV)

- 100.3

- 78,5

- 49.7 20.8 + 5.9 + 32.4 «Π5

1.3 χ, 0 * ² 2.5 x, 0 1.2 x, 0 8.1 x 10

Claims (1)

OBJECT OF THE INVENTION A membrane for a calcium ion selective electrode consisting of a plastic film, such as polyvinyl chloride, plasticized with a plasticizer, such as o-nitrophenyl-n-alkyl ether, characterized in that it contains as a neutral carrier a 3,6-dioxacorkic diamide whose amide nitrogen atoms are substituted symmetrically and two phenyls two mA 2n alkyloxyethyly, the schematic structural formula wherein R is an n-alkyl group ^H2n + 1 ° P ® ^{8 TEM} of carbon atoms from 8 to 11, such as N, N'-diphenyl-N, N, N'-di-2-n-octyloxyethyl) 3,6-dioxacorkic acid diamide or N, N'-diphenyl-N, N'-α (2-n-4-decyloxyethyl) 3,6-dioxacorkic acid diamide.