CS242593B1 - Chemically modified mercury film electrode - Google Patents

Abstract

The solution relates to a modified mercury film electrode, in which the mercury film is covered with a film of plastic, for example polyvinyl chloride, containing tri-n-octylphosphine oxide. The electrode can be used in the field of inorganic electrochemical analysis of solutions.

Description

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Chemically modified mercury film electrode

The invention relates to a modified mercury film electrode in which it is mercury. a film coated with a plastic film, such as polyvinyl chloride, containing tri-n-octylphosphine oxide. The electrode can be used in the field of inorganic electrochemical solution analysis.

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The invention relates to chemically modified mercury film electrodes for electrochemical measurements, in particular indicating electrodes for voltammetric and potentiometric determination of certain ions.

Various types of electrodes are used in electrochemical measurements. Thus, mercury electrodes have the most prominent position in the voltammetric determination of some ions, especially for their wide cathodic potential range. Smaller applications are found in solid electrodes, such as glass carbon electrodes, which are used more frequently as mercury film carriers.

Voltammetric determination of ions with these electrodes is in many practical applications of low selectivity and requires preliminary separation of determined ions from interfering ions by a suitable separation method.

However, the use of the separation method increases the complexity and time-consuming nature of the entire assay procedure. Therefore, a pathway has been proposed by chemical modification of the electrode surface by ion exchange and extraction systems. Izutsu achieved promising results with his co-workers, as described in Anal.Chim, for example. Acta 149,147,1983 and Lubert et al., Described in Anal. Chim. Acta 144, 123, 1982, which modified the glassy carbon electrode with tri-n-octylphosphine oxide. Electrodes prepared by them, like unmodified solid electrodes, have limited use and lack of activity stability in practical analyzes.

The above-mentioned drawbacks are overcome by the chemically modified mercury electrode of the invention. The principle of the electrode is that it consists of a mercury film on silver as a carrier, which is covered with a plastic film, for example polyvinyl chloride containing tri-n-octylphosphine oxide.

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The main advantage of the electrode according to the invention is the possibility of its wider application in inorganic electrochemical analysis. By changing the composition of the analyzed solution it is possible to vary the sorbability of individual ions to a considerable extent and to achieve a good distribution of the determined ions from interfering ions. The actual measurement, for example by a voltammetric technique, is most often performed after replacement of the analyzed solution with a suitable base electrolyte. Thus, high selectivity of the assay can be ensured. The electrode can also be used as a potentiometric sensor. The electrode activity is sufficiently stable and convenient for practical use. The time during which the electrode can be used depends on both the composition of the solutions to be analyzed and the measurement technique and method of electrode regeneration. The electrode of the invention combines the advantages of a mercury electrode with a high separating capability of a tri-n-octylphosphine oxide-containing film.

The electrode preparation process of the present invention consists in forming a mechanically stable and uniformly distributed mercury film on the surface of the silver disc electrode and stabilizing the tri-n-octylphosphine oxide on the mercury film surface by depositing it in a suitable plastic film, such as polyvinyl chloride.

In the following, the invention is illustrated in more detail by means of exemplary embodiments.

Example 1

The surface of the support, silver disc electrode with a diameter of 3 mm, is first sanded with abrasive papers, degreased in ethanolic potassium hydroxide solution KOH for two minutes with ultrasound, rinsed with water, dried with warm air and spread about 0.5 mg of silver amalgam. 5 µL of a 5 mM solution of tri-n-octylphosphine oxide in tetrahydrofuran containing 10% w / w high-viscosity polyvinyl chloride / tri-n-octylphosphine oxide is pipetted onto the mercury film thus prepared. After evaporation of the solvent, the electrode is ready for use.

Example 2

The surface of the carrier, the 3 mm diameter glass electrode, is regrinded with abrasive paper, degreased in ethanolic potassium hydroxide solution KOH by ultrasonication for two minutes, the electrode is rinsed with water and electrolytically deposited on its surface.

- 3 242 593 silver from a solution containing 0.1 M ammonium hydroxide NH4OH, mM Ag (CN) dicyanostriquate and 1 mM CN cyanide at a potential of - 1.00 V against a saturated calomel electrode for 20 minutes.

After rinsing with water and changing the electrolyte with a solution containing 0.1 M hydrochloric acid and 5 mM mercuric chloride HgCl2, the surface of the silver film electrode is electrolytically deposited by mercury at a potential of -0.50 V against a saturated calomel electrode for 5 to 10 minutes. The electrode is rinsed with water, dried with warm air and pipetted onto its surface with a 5/1 5 mM solution of tri-n-octylphosphine oxide in tetrahydrofuran containing 10% w / w high molecular weight polyvinyl chloride / tri-n-octylphosphine oxide. After evaporation of the solvent, the electrode is ready for use.

The example below illustrates the operation of the electrode of the invention. Example 3

Determination of bismuth by galvanostatic dissolution analysis. The solution of composition was analyzed: 0.5 M hydrochloric acid HCl, 0.4 M -1.5 + phosphoric acid H 2 PO 4 containing 0.5 gml of Bismuth Bi. The bismuth was first accumulated on the surface of the electrode disconnected from the potentiostat in the stirred solution for 80 seconds, then the electrode was rinsed with water, the sample solution was replaced with a basic electrolyte with 0.5 M hydrochloric acid containing no Bismuth ⁺ and bismuth retained on the indicator electrode. determined by galvanostatic dissolution analysis. At a potential of 0.300 V against a saturated calomel electrode, within 40 seconds, the bismuth Bi ^{+ was} reduced to a metal, which was then oxidized with a current of 5 / z A. The dependence of the indicator electrode potential over time during the bismuth oxidation was registered. The transient state in this case was about 2 seconds. Before further determination, the electrode was regenerated in a stirred solution of 3 M sulfuric acid H 2 SO 4 for 80 seconds.

The chemically modified mercury film electrodes of the invention can be utilized in the field of inorganic electrochemical analysis to determine concentrations of certain ions.

Claims (1)

SUBJECT OF THE INVENTION 242 S93 A chemically modified mercury film electrode formed by a mercury film on silver as a support, characterized in that the mercury film is covered with a plastic film, for example polyvinyl chloride, containing tri-n-octylphosphine oxide.