RU2399040C1 - Copper-selective electrode membrane - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: copper-selective electrode membrane contains electrode-active material in form of amberlite JRA-400 - zincon (AMB-ZN), plasticiser in form of dioctylphthalate (DOP), polyvinylchloride and has the following ratio of components, in wt %: electrode-active component (AMB-ZN) - 2.5-3.41; plasticiser (DOP) 69-79; polyvinylchloride 24.39. ^ EFFECT: obtaining a chemically stable highly selective copper-selective membrane for quantitative determination of content of copper in environmental media. ^ 2 cl, 3 dwg, 3 ex, 4 tbl

Description

The invention relates to ionometry, potentiometric methods of analysis and control of the concentration of ions in aqueous solutions and can be used in the chemical, metallurgical industry, in optical chemistry, in scientific research as a sensitive element of an ion-selective electrode (chemical sensors) for quantitative determination of the concentration of copper ions in water solutions. The invention is directed to the creation of a membrane composition of an ion-selective electrode (ISE), which allows to find materials intended for use as a sensitive element of an ion-selective electrode (chemical sensor) for the quantitative determination of the concentration of copper ions in aqueous solutions.

Solid membrane electrodes sensitive to copper (II) ions were first obtained by Ross. (one)

These electrodes resulted in noticeable changes in the surface layer. The Orion company produces copper selective electrodes. But they have their drawbacks: the test solution should not contain ions: Cl ^- , Fe ³⁺ , Cd ²⁺ , which interfere with the determination of micro amounts of S ^2- , Ag ⁺ , Hg ²⁺ .

The Czechoslovak company Crutur manufactured Cu ²⁺ - selective electrodes with a copper powder membrane with embedded CuS, as well as a silicone rubber membrane with embedded Cu ₂ S (2).

The disadvantage is the low selectivity in the presence of transition metals.

Closest to the proposed invention (prototype) is (3).

The composition of the membranes of the ion-selective electrode for determining lead ions, including the electroactive component, plasticizer, polyvinyl chloride and lipophilic additive, contains dipicolinic (2,6-pyridinedicarboxylic) acid diamide as the electroactive component, and dioctyl sebacinate (DOS) as the plasticizer, additives - chlorinated cobalt dicarbolide (CDK), while the composition has the following ratio of components, wt.%: electroactive component - 1.0-3.0; plasticizer (DOS) - 60.0-75.0; lipophilic additive (CDK) - 0.1-0.5; polyvinyl chloride - the rest.

In addition, various dipicolinic (2,6-pyridinedicarboxylic) acid diamides can be used as the electroactive component.

A significant drawback of the above sensors is low mechanical strength, short service life (several weeks) and insufficiently high selectivity, in particular in the presence of concomitant transition metals; low chemical resistance and inability to work in a wide pH range.

The objective of the invention is the expansion of a number of ion-selective electrodes (chemical sensors) and the use of new solid phases in the analysis of environmental objects.

The technical result in the creation of a copper-selective membrane, necessary for the quantitative determination of copper content in environmental objects.

The specified technical result in the presence of transition metals is achieved by the fact that the membrane of the ion-selective electrode for determining copper includes the solid phase amberlite JRA-400 - zinc (AMB-TsN), which was obtained by immobilization of a selective organic reagent 5- (2'-carboxyphenyl) - 1 (2 "-hydroxy-5'-sulfo-3'-phenylformazan), known as zinc, on a strongly basic polystyrene base anion exchange resin (JRA-400).

The essence of the invention lies in the fact that the composition of the membrane of the ion-selective electrode for determining copper ions, including the electroactive component, plasticizer, polyvinyl chloride, contains as an electroactive substance, JRA-400 amberlite - zinc (AMB-TsN), and dioctyl phthalate (DOP) as a plasticizer. , while it has the following ratio of components, wt.%

Electroactive component (AMB-TsN) 2.5-3.41

Plasticizer (DOP) 69-79

Polyvinyl chloride 24.39

In addition, this result is achieved by the fact that the used electroactive component contains formazan rings forming a chelate with copper.

The authors draw such a conclusion on the basis of the research results obtained, i.e. the practically minimal effect of the structure and the presence of phage in Zinc on the properties of the obtained membrane ion-selective electrode based on the known data of solid-phase spectroscopy (4).

The immobilization of components (solid phases) in the membrane of an ion-selective electrode, traditionally used in solid-phase spectroscopy, makes it possible to develop an ion-selective electrode with a variable composition and properties.

Example 1

An ion-selective electrode membrane is prepared by dissolving selected weighed portions of all starting materials: 0.07 g AMB-CN; 0.5 g of PVC; 1.5 DOF.

For the manufacture of the membrane (disks 10 mm in diameter), in an inert solvent cyclohexanone (CT) with a volume of 10 ml, with constant stirring, add PVC, DOP and AMB-TsN in wt.%: 24.39% (PVC), 73.17% (DOP) and 3.41% (AMB-CN). The homogeneous mixture was poured into a Petri dish and dried at room temperature. Disks are cut out of an elastic film and glued (using a solution of PVC in a CT) to the ends of the polyvinyl chloride tubes. After drying, a 0.01 M solution of CuCl _{2 is} poured into the electrode and immersed in a solution of the same composition, where they are recommended to be stored between measurements. The calibration graph of the copper membrane in HCl solutions is shown in figure 1. The angular coefficient of the electrode function is close to theoretical in the concentration range: 1 · 10 ^-4 -1 · 10 ^-5 .

Example 2

The ISE membrane is synthesized as described above (Example 1), and for preparation, the following ratio of components in wt.% Is taken: AMB-TsN - 2.8, DOP - 79, PVC - stop.

Example 3

The ISE membrane is synthesized as described above (Example 1), and for preparation, the following ratio of components in wt.% Is taken: AMB-TsN - 2.0, DOP - 68, PVC - the rest.

All investigated electrodes containing the above components in the claimed concentration range exhibit a similar function.

The electrode characteristics of the membranes were measured by measuring the emf of a galvanic electrode

The dependence of the EMF of such an element on the change in the ions to which it was created is determined by the well-known equation:

E = E ⁰ + (0.059 / n) logC _{m (Cu)}

Table 1 shows the results of ISE calibration in aqueous solutions of CuCl ₂

Table 1 E, mV 135 180 230 270 320 325

1 · 10 ^-5 1 · 10 ^-2 1 · 10 ^-3 1 · 10 ^-4 1 · 10 ^-5 1 · 10 ^-6 pC _Cu one 2 3 four 5 6

Figure 1 presents the calibration results of ISE in aqueous solutions of copper (II) chloride. The range of straightness of the electrode potential from the activity of copper ions in aqueous solutions is five orders of magnitude. As can be seen from figure 1, the slope index (angular coefficient) mV / pC _Cu is 50 mV, since the ideal slope of the ion-selective electrode created on a doubly charged ion, according to the Nernst equation, should be approximately 29 mV, the anomalous value of the angular coefficient is a consequence of the superposition of the electrode functions of a hydrogen ion due to the hydrolysis of a copper (II) ion. To confirm this assumption and in order to clarify the natural electrode function of the membrane based on modified sorbents, additional studies of the membrane electrode were conducted on standard hydrochloric acid solutions and on copper (II) chloride solutions prepared on a 0.1 M sulfuric acid solution (Table 2, figure 2 and table. 3, figure 3).

Figure 2 presents the calibration results of ISE AMB-CN in hydrochloric acid. Figure 3 presents the calibration results of the ISE AMB-CN in sulfate solutions of copper (II) chloride.

table 2 E, mV 180 195 205 220 235 230 pH one 2 3 four 5 6

Table 3 E, mV 175 195 200 215 230 232 pC _Cu one 2 3 four 5 6

Therefore, the electrode we obtained can be proposed as a membrane electrode for the quantitative determination of copper (II) and an alternative glass hydrogen electrode.

Checking the selectivity of the copper-selective electrode with an AMB-TsN membrane showed that in the acetate buffer the claimed compositions have absolute selectivity to copper. The experimental data did not reveal the sensitivity and selectivity of the membranes to other ions (Table 4).

Table 4 Slope, mV / pX Membrane (Example No.) Zn ²⁺ Cd ²⁺ Pb ²⁺ Cu ²⁺ AMB-TsN PVC DOF (1) 0 ± 1 0 ± 1 1 ± 1 29 ± 2 AMB-TsN PVC DOF (2) 1 ± 1 0 ± 1 0 ± 1 30 ± 2 AMB-TsN PVC DOF (3) 0 ± 1 1 ± 1 1 ± 1 27 ± 2

The data from laboratory studies confirm the technical result.

The advantages of the proposed method:

- Significant chemical stability of the membrane in various reaction media: 6 M solutions of acids, alkalis; organic solvents (ethanol, acetone, dioxane, etc.)

- Increasing the selectivity (selectivity) of the membrane to copper (II) ions in the presence of transition metals, as well as macro and micro components of various objects.

- A significant increase in the coefficient of selectivity to copper ions in the presence of transition metal ions accompanying in objects up to 10 ^-5 , gives great opportunities for real determination of copper in many technological solutions, wastewater, food objects.

- The high chemical stability of the obtained membranes makes it possible to determine copper ions in strongly acidic media (pH <0).

- Ability to control the acidity of the medium.

Literature

1. Nikolsky B.P. Ion exchange and ionometry. - L .: Leningrad State University, 1979.

2. Nikolsky B.P. Ion-selective electrodes. - L .: Leningrad State University, 1980.

3. RF patent No. 2315988, priority 08/28/2006, published. 01/27/2008. "The composition of the membrane of the ion-selective electrode for the determination of lead ions."

4. Tataeva S.D., Korenman Ya.I. and others. The journal "Sorption and chromatographic processes." 2005, No. 5. S.696-703. "Sorption of copper (II) on anion exchangers with immobilized formazan moiety."

Claims (2)

1. The membrane of the copper selective electrode, including the electroactive component, plasticizer and polyvinyl chloride, characterized in that the membrane contains as an electroactive substance - JRA-400 amberlite - zinc (AMB-CN), as a plasticizer - dioctyl phthaleate (DOP), while it has the following ratio of components, wt.%:
Electroactive component (AMB-TsN) 2.5-3.41 Plasticizer (DOP) 69-79 Polyvinyl chloride 24.39 2. The membrane according to claim 1, characterized in that the electroactive component contains formazan rings forming chelates with copper.

Images