SU1562829A1 - Composition of membrane of ionoselective electrode for determining mercury (ii) - Google Patents

Abstract

This invention relates to analytical chemistry, in particular, to methods for potentiometric analysis of mercury-containing solutions using ion-selective electrodes. The aim of the invention is to increase the selectivity and decrease the detection limit of mercury (II). For this purpose, didecylaminoethyl-β-tridecylammonium tridiodomercurate is used as an electrode-active component in the membrane. The use of the invention allows the determination of mercury (II) in the concentration range 10 ^{-7-2 .} 10 ³ M in the presence of large excess foreign ions. The invention can be used to analyze natural and industrial objects. 1 dw., 2 tab.

Description

The invention relates to analytical chemistry, in particular, to methods for potentiometric analysis of mercury-containing solutions using ion-selective electrodes, and can be used in the practice of analytical services to monitor the content of mercury (II) in a number of natural, biological and other environmental objects, as well as for rapid mercury (II) process control in industry.

The purpose of the invention is to increase the sensitivity and selectivity of the determination of mercury (II).

This goal is achieved by the fact that the composition of the membrane of an electrode selective to mercury (II) containing a polyvinyl chloride matrix plasticized with dioctyl phthalate, as an electrode-active substance, contains a dodecylaminoethyl-Y-tridecyl ammonium tridihydromercuriate. i

The drawing shows the dependence of the potential of the electrode, with a membrane selective to mercury (II), on the concentration of mercury (II) in solution against the background of 10-M Nal (n 1, 2, 3) at pH 11 (carbonate buffer).

As can be seen from the drawing, the detection limits for mercury (II) are (G, 1.3 -11G7 and 5-1CT7M / dm3 with iodide background concentrations 1 (GE, 1HЈ and 1U M, respectively. Slope of electrode functions is 59 mV / pHg , which corresponds to the reversibility of the membrane to the single-charge HgI3 anion, which in the proposed method is chosen as the analytical form of mercury (II).

The selectivity of the proposed membrane compositions was determined by the method of mixed solutions at a fixed concentration of an interfering ion l Meiuj 0.1 M against the background of 0S01 M KI at pH 10-11. The data obtained are shown in Table. one .

The service life of the electrodes for at least a year, the response time does not exceed 1 min, the reproducibility of the potential, + U-- 2 MB.

The dependence of the electrochemical parameters of the electrode, selective for the mouth ™ type (II), on the concentration of the iodide background is presented in Table 2.

As follows from Table 2, the best electrochemical parameters are observed at iodide fund concentrations of 10–10 M. At lower iodine concentrations of ions, the deterioration of electrochemical parameters is due to the dissociation of the anionic complex, which is an analytical form of mercury (II) in the proposed method. In addition, the electrode operation interval is very narrow. At concentrations above 10 M NaCl, the deterioration of the electrochemical parameters is due to a decrease in the concentration of Hgl3 due to the formation of a two-charge HgI4 ion having a low affinity to the membrane phase,

Example, Preparation of a membrane of an ion-selective electrode for the determination of mercury (II).

A weighed portion of 2 g of polyvinyl chloride was transferred to a tube, 6 g of a dioctyl phthalate plasticizer was added and mixed to obtain a homogeneous mixture. Then, 20 ml of piclohexonone was added to the tube and the mixture was heated at 4b-50CC until sweaty HBH was heated. At lower temperatures, the process of dissolving PVC is very long; at large temperatures it is possible to destroy it. PEFRN — 0.02 tridiidomerkurnat didecylaminoetite

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- i-tridecylammonium and outweigh until it is completely dissolved. After that, the mixture is poured into a Petri dish and dried to complete evaporation of cyclohexanone (3-6 days). The ratio of ingredients in the resulting membrane is the following, wt.%:

Triiododomekuriat 0,06-1

Didecylaminoethyl-ft-tridecylammonium

dioctyl phthalate 60-80

Polyvinyl Rest

The ratio in the PVC membrane to the plasticizer in the specified amounts does not significantly affect the electrochemical parameters of the chon-selective electrode. At less than 50% plasticizer concentrations, the mechanical stiffness and electrical resistance of the membranes increase, which leads to potential instability and makes it difficult to work with it. At plasticizer concentrations greater than 80%, the mechanical properties of the membranes are markedly impaired.

A noticeable effect on the electrochemical parameters of the electrode is exerted by the concentration of the electroacoustic substance of the membrane. The best parameters are observed at concentrations of the electrode-active substance of the membrane of 0.06-0.6 wt.%: At lower concentrations of the electrodeactive substance, the ion-exchange properties of dioctyl phthalate appear (due to impurities). At higher concentrations, the increase in the detection limit is associated with a stronger yield of the scattering ion from the membrane phase to the boundary solution phase. In general, such deterioration leads to the impossibility of achieving the goal.

The use of the proposed membrane composition makes it possible to significantly increase the sensitivity and selectivity of the determination of the crush (II) in comparison with the known ones. This will allow the determination of mercury (II) using the direct method of concentration measurement in the concentration range of 10 -2-10 M, depending on the concentration of the iodide pool in the presence of large excess of foreign ions.

Claims (1)

The membrane proposed composition can be used; n express control of otupi (II) in a group of objects of the field, also in other areas of vapor analysis needing express, highly insensitive and selective methods for analyzing mercury-containing solutions . Invention Formula The composition of the membrane of the ion-selective electrode for the determination of mercury (II) in solutions containing iodide ion, including polyvinyl chloride as a matrix, dioctyl phthalate as a plasticizer, and an electro-active component that distinguishes In order to increase the selectivity and decrease the detection limit, the salt of the tridiidomercurate didecylaminoethyl-β-p-tridecylammonium was used as the electrode component with the following ratio of ingredients, wt.%: Electro-active component0, 06-1 Plasticizer60-80 Polyvinyl chloride Rest  Jre Mesh ions . GG 6.3-510 L -10 1-Yu-5  THOSE 4.5 10 Continuation of table 1 CNS С104 Mesh ions Ay Pot . NC TO 2.2 1U 4, L 10 2.3 5, Z.b-KG5 4, 56 59 59 59 56 IS Table 1 5L4 8 th 6 b, 1, Continuation of table 1 CNS С104 Table  - 2-S 5 - 2-10 1.3 MO 7 - 2-S 3  - - 70Starting A.Kopytin Editor N.Lazarenko Tehred M.Hodannch Order 1061 Circulation Y4 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 f -tytoffM) Proofreader M.Sharoshi Subscription