SU898314A1 - Ion selective membrane electrode - Google Patents

Description

The invention relates to ion-specific electrodes based on neutral carriers and is intended to determine the HanpHMepi ammonium and potassium ions in aqueous media. Ion-selective membrane electrodes are known, consisting of a plasticine-chloride body, at the lower end of which an indicator membrane is glued, the composition of which is determined by the nature of the ion being monitored. An aqueous solution of a specific ionic composition is poured into the housing. A current & half half element Cl is screwed into the housing. Such electrodes cannot be used in biology and medicine because of their large dimensions due to the presence of a liquid filler. Closest to the invention are membrane electrodes with a solid electronic conductor and a membrane based on neutral carriers impregnated into the polymer matrix using plasticizers. The polymer matrix is in direct contact with a solid current collector 121. The electrodes showed sufficient reproducibility of the potential values, but unsatisfactory stability of the readings over time. This makes it necessary to calibrate the electrodes daily. The lifetime of such electrodes is short — about a month. The aim of the invention is to improve the stability of the electrode readings. The delivered chain is achieved by the fact that in an ion-selective membrane electrode with a solid electronic conductor and a membrane based on neutral carriers impregnated into the polymer matrix with plasticizers, between the electronic conductor and the conelective membrane: intermediate layers (at least two) from the membrane are sequentially placed in the direction to the membrane an electronically conducting substance, a substance forming a buffer system in pH and pM, a substance composed of 38

The first oxide is a reduced sodium carbon dioxide.

Intermediate spikes between the electronic conductor and the ion-selective membrane consistently contain, weight. %:

I layer

Electrodynamic substance34.0-40.0

The substance making up the redox system is 28.0-35.0.

Substance forming

buffer system

on rn1,6-2,0

Substance forming

system on рМ3,4-4,0

Conductive conductive

substance25,4-26,6

And layer

Electrodynamic

substance45.0-53.0

The substance constituting the redox system 18, O-24, O The substance forming

buffer system in pH 4.0–6.0 Substance forming a buffer system in pM 7.5–12.5 Electroconductive

substance14,5-15,5

The drawing shows the electrode, the axial section.

Electronic conductor 1, made in the form of a graphite rod, zaklk. chen into tube 2 of plasticized polyvinyl chloride. Copper wire 3 is attached to the electronic conductor 1 at one end, and intermediate layers 5 and 6 (at least two) are applied to the other end of the conductor between it and the membrane 4

So, the working part of the electrode consists of several layers, including the Electroactive substance, the substance constituting the redox system, the substance forming the buffer system in pH, the substance forming the buffer system in pM, the electron conductor five more substance.

Membrane layers are prepared as follows.

The components of the membrane - Electrodioactive substance - are dissolved in cyclohexanol, redoxite EO-7 or heme (as a substance constituting the redox system), KU-2 i resin in H- and M-forms ( as buffering agents

144

system for pH and pM, respectively)

carbon black (as an electron conductor

substances).

The mixture with the following ratio of components, weight. %:

Components membranes37,0

Oxidation-reduction system - redoxite ESC-732.0 Buffer system for pH KU-2 in H-form1, E Buffer system for PM KU-2 in M-form 3.4 Electroconductive substance - soot 26.0 is thoroughly mixed on a magnetic broom for 1 h at room temperature. This mass is applied to the electronic conductor as the first layer (layer thickness, 5 mm; mass is allowed to dry, after which a second layer is applied, the thickness of which is also ≈ 0.5 mm, and the ratio of components is as follows, wt.%:

Membrane components49,0

The redox system EO-7, hem21,0, redox system

Buffer system for pH - KU-2 in H-form5.0

Buffer system for pM - KU-2 in M-form10.0

Electrically conductive substance - soot15,0

The second layer is also given the opportunity to dry out (24 hours).

Then a third layer is applied - the actual ion-selective membrane. The latter is prepared in a manner already known, by dissolving and displacing the polymer (polyvinyl chloride), the plasticizer (dibutl phthalate, dioxtil phthalate, etc.) and the neutral carrier with stirring and heating to 40-45 ° C.

The electrodes thus obtained are allowed to stand for another 24 hours to dry the third membrane layer (complete solvent: cyclohexanol), after which the electrode is ready for operation.

The manufacture of the membrane by the described Method is due to the need for a smooth transition from electronic to ionic conductivity. Therefore, the first membrane layer, in contact with the electronic conductor, is designed in such a way that it provides high electronic conductivity and a certain ionic component, the second layer - a large ionic component.

Claims (1)

Claim An ion-selective membrane electrode containing a current collector with a neutral carrier-based membrane deposited on it, a plasticizer and a binder, characterized in that, in order to improve measurement stability, at least two intermediate layers containing membrane components are sequentially placed between the current collector and the membrane, oxidatively -reduction system, pH and pM buffer system, electronically conductive substance, insoluble in water, in the following ratio of components, weight. %: ί layer Oxidation Reduction Membrane Components 34-40 innovative system 28-35 5 PH buffer system RM buffer system Electronically conductive 1.6-2.0 3.4-4.0 10 substance 25.4-26.6 ί layer Oxidation Reduction Membrane Components 45-53 innovative system 18-24 1S PH buffer system Buffer system by 4.0-6.0 rM Electronically conductive 7.5-12.5 20 substance 14.5-15.5 Sources of information, taken into account during the examination 1. Ion-selective electrodes. Under 2 $ ed. R. Darsta, 1972, p. 68-69. L. H. Wlraba Copper- (r) Suenae impreqjndt SiKioone rubber membrane asbetective electrode £ or Copper (d) ion, ταδαηta, Al, 19? O, R. B03.