US3855097A - Ion-selective electrode - Google Patents

Ion-selective electrode Download PDF

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US3855097A
US3855097A US00264390A US26439072A US3855097A US 3855097 A US3855097 A US 3855097A US 00264390 A US00264390 A US 00264390A US 26439072 A US26439072 A US 26439072A US 3855097 A US3855097 A US 3855097A
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ion
electrode
radical
salt
electroactive
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M Sharp
G Johansson
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/333—Ion-selective electrodes or membranes
    • G01N27/3335—Ion-selective electrodes or membranes the membrane containing at least one organic component

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  • ABSTRACT consisting of a salt in which one ion is a radical-ion. Said electroactive plate is selective to the specific ion.
  • the invention is concerned with an ion-selective electrode for measuring the concentration of ions in a solution.
  • the activities of ions in solution can be determined with an electrochemical cell.
  • This well-established technique exploits electrodes of the type where the potential of this electrochemical half-cell is determined by the activity of chloride ion in the solution.
  • a complete cell'must necessarily consist of two such half-cells.
  • the glass electrode employed for pl-l-measurements may be cited.
  • the glass forms a membrane which is supplied with electrical contacts as follows
  • the complete half-cell (2) constitutes the glass electrode, or, when the membrane consists of a different material, represents the general construction of many ion-selective electrodes.
  • a particular example of an ion-selective electrode may be written Ag,AgCl/K Cl, FlLaF membrane/F
  • the electrode potential changes when the fluoride ion activity in the test solution is altered (British Pat. No. 1,131,574).
  • the half-cell (1) may be placed in a special chamber which contains a solution of known constant chloride ion activity. Electrical contact to the remainder of the cell is made through a liquid-junction. Such an arrangement effectively maintains the potential of the half-cell constant, and this can be used as a reference point for further potential measurements.
  • This assembly is known as a reference electrode.
  • E E, RT/nF The activity of fluoride ion in a given solution can be determined with the aid of the ion-selective electrode (3). If the potential difference between the two halfcells is measured with a voltmeter, the following relation, called Nernsts law, is obtained E E, RT/nF In [F'] where E represents the measured potential, E is constant, R the gas-constant, T the absolute temperature, n the valence of the measured ion, F the Faraday and [F'] the fluoride ion activity or concentration.
  • Interference by an ion of typej upon an electrode supposedly selective to reference ion, i may be represented by a mixed response equation.
  • the electrode of the invention comprises an ionselective electrode for the analysis of the concentration of inorganic, organic and metal-organic ions in a solution, comprising an electrically insulating electrode holder, an electroactive plate in said electrode holder, and an electric conductor connected to said electroactive plate, and is characterized in that the electroactive plate consists of a salt in which one ion is a radical-ion.
  • the countepion is preferably the ion to be determined in a test solution.
  • the counter-ion may be an inorganic, organic, or metal-organic ion.
  • the essence of the invention is the use of radical-ion salts as electroactive substances in ionselective electrodes.
  • X represents the groupings specified for the compound (1).
  • This compound (ll) is ion-selective for where X may be H, CH3. CH C -,H, or higher hydrosilver, copper. nickel, and other ions. carbon chain, OCH OC H or other alkoxy-grouping,
  • X5 -NH2 (IN X4 3 X2 X1 vm X6 X7 xx 1 X CN u X1
  • X -, H, Cl, Br, I, F, CH C H or other aliphatic X4 X3 X0 hydrocarbon chain and other Xs represent the group- J; IV ings specified for the compound (Vl).
  • X and X may be O, or Substituted thianthrenes may also be used:
  • Benzothiazolone azine. (Xll) and similar compounds form radical-cations which yield salts suitable for electrodes showing high selectivity towards perchlorate. perrhenate. tetrafluoroborate and iodide ions.
  • R is an alkyl group.
  • a mixture of two or more radical-ion salts is often to be recommended, because the electrode becomes more stable and less sensitive to light.
  • Electroactive materials may be prepared in general from substances of types I Xll by suitable oxidation or reduction and precipitation methods. If the radical is an anionic radical. it is preferred first to prepare an easily soluble salt of the radical. for example the sodium or lithium salt. Said salt is now reacted with. for example. Agfl Cu. Ni, Co. Pb, Zn, Cd'. Hg2+ Hgz'li 112+ Ti-H" v4+, VO2+ Alibi S -i-i S 2+ Ca NHJ' to form a salt having a low solubility.
  • the radical is an anionic radical. it is preferred first to prepare an easily soluble salt of the radical. for example the sodium or lithium salt. Said salt is now reacted with. for example. Agfl Cu. Ni, Co. Pb, Zn, Cd'. Hg2+ Hgz'li 112+ Ti-H" v4+, VO2+ Alibi S -i-i S 2+ Ca NHJ'
  • This salt after purification and drying, may be pressed to form electroactive plates at an adequate pressure, usually l.000-l0,000 kg/cm
  • the radical is a cationic radical it is preferred first to prepare an easily soluble salt, such as the acetate, and to react said easily soluble salt with, for example C10 SO PO HPOE".
  • an easily soluble salt such as the acetate
  • an easily soluble salt with, for example C10 SO PO HPOE.
  • l-l POf, ReOf, I0 BrOf, MnOf, SCN', N0 7, S 0 CN, 8*, Fe(CN) FE(CN).;” to form a salt having a low solubility, which is now purified, dried, and pressed to form an electroactive plate.
  • Counter-ions are (C6H5)4B+ (CH3)4N+, (C2H5)4N+, 3 7)4 v -I Q)'1 Q e 5)4 6 5)4 a (C H Sb (CH )Hg (C H )Hg methoxyethyl mercury ion, ethoxyethyl mercuryv ion, anions and cations of amino acids, and ions of a quaternary ammonium compound having the structure in which R is hydrogen, an alkyl or an aryl group, at least one substituent being an alkyl or aryl group.
  • the electroactive plate obtained can be mounted in various ways in the electrode holder.
  • Sealing between the electroactive plate and the insulating electrode holder may be effected by in situ pressing or by the use of an appropriate adhesive, e.g., epoxy-resin or silicone rubber.
  • An alternative method of mounting the electroactive plate is to put it in contact directly. or through some conducting material such as graphite paste, with a metal base which is fitted with a contact. All conductive surfaces except that of the electroactive plate are insulated, e.g., with plastic-enamel or silicone rubber.
  • the electronic conductivity exhibited by radical-ion salts allows such dry contact constructions to be fully exploited.
  • a further method involves dissolution of the radicalion salt in an otherwise inert plastic matrix in such a quantity that the resulting composition possesses suitable electrical resistance.
  • the copper salt of DTF may be dissolved in polyacrylonitrile in a quantity of 5 50 percent by weight, for example, and the dried film may be mounted as a membrane or electroactive plate as described above.
  • the electro-active material may also be precipitated directly upon a metallic conductor. Radical-ion salts may be formed upon the surface ofa conductor during electrolysis. Perchlorate sensitive plates of the compound Vlll have been made in this way with conductors of platinum or graphite.
  • liquid membrane constructions may be applicable.
  • the liquid may be absorbed by a sintered glass or ceramic disc which provides the mechanical support for the membrane or plate.
  • FIG. 1 shows an apparatus containing an electrode according to the invention.
  • FIG. 2 shows another embodiment of the elctrode.
  • FIGS. 3-6 illustrate the results of measurements with various electrodes according to the invention.
  • the apparatus of FIG. 1 comprises a vessel 8 for a test solution 5, a measuring electrode 6, a reference electrode 7, and a voltmeter 10.
  • the measuring electrode comprises a tubular electrode holder 6 of glass.
  • the lower end of the tube 6 is closed by means of an electroactive plate 1 consisting of the copper salt of DTF.
  • the tube 6 is partially filled with a solution of CuCl
  • a silver wire 3 having a surface coating of AgCl extends down into the solution 2.
  • the upper end of the silver wire is connected to the voltmeter 10.
  • the reference electrode 7, known per se, has a similar structure, but its bottom opening is closed by means of a plug 9 of, for example, asbestoes fibres or a glass filter.
  • the silver wire 4 is connected to the voltmeter 10.
  • an electroactive plate 21 has been fastened to a metal base 23 by means of a graphite layer 22.
  • a metal wire 24 is fastened to the metal base 23.
  • the assembly is covered with a layer 20 of plastic-enamel, the layer 20a covering the main part of the metal wire 24, the layer 20b covering the metal plate 23, the graphite layer 22 and the electro-active plate 21 except for its external main surface.
  • the upper-curve 31 represents the lead salt of TNAP
  • the lower curve 32 represents the lead salt of DTF. Both electrodes are useful as lead ion activity indicators over a wide range, IO M Pb. Li, Na K. Ca N ions do not interfere. Cu, Ag* and Hg ions interfere strongly and should be present in low concentrations during lead ion activity determinations.
  • the upper curve 51 represents the tetraphenylarsonium salt tetraphenylarsonium DTTF
  • the lower curve 52 represents the tetraphenylarsonium salt of DTF.
  • These electrodes have been used to titrate perchlorate ion with tetraphenylarsonium chloride ion potentiometrically.
  • the slope of the line in FIG. 5 should have been 59.2 mV per decade at 25C. It has been found that the purity of the material influences the slope greatly. the purer the material the more nearly the slope approaches ideality. The preparative method is also of importance. Poor electrode behaviour can arise from cracks or pits which are formed in the electroactive plate. Optimum conditions appear to involve pressing at 700 kg/cm and 120C under vacuum with teflon-coated. diamond-polished die faces.
  • the platinum base was previously cleaned electrolytically.
  • Tolidine perchlorate was formed directly upon the metal.
  • Other ions e.g., halide, show low interference during perchlorate ion activity determination.
  • otolidine may be oxidised chemically in the presence of perchlorate ions, whereupon the desired electroactive material is obtained as a precipitate.
  • ion selective electrodes for cations may be prepared from radical-ion salts derived from structures l-V.
  • Cations may be chosen widely and may include organic and organometallic types.
  • Electrodes selective to anions may similarly be derived from suitable radicalcation salts.
  • K in equation (6) reflect only slight interference by other ions.
  • Values of K for an electrode made from benzothiazolone azine perchlorate, Xll, were found to be for CI 8.5 10', N0 1.1 lO, Br 7.4 10 F 5.1 l0", Ac 4.6 10 OH 8.3 10*, C10,, 9.1 10
  • the perchlorate ion activity range was 0.1 M 10* M. Iodide should not be present in concentrations greater than one-hundredth that of perchlorate ion.
  • the preparation of ion radical electrode materials can be made as follows.
  • the ion radical can be prepared by dissolving 380 mg 9-dicyanomethylene-2,4,7-trinitrofluorene in acetonitrile and adding 200 mg lithium iodide dissolved in acetonitrile. The solution is boiled for ID minutes, and is allowed to cool. A black precipitate forms and it is filtered off, washed with a small quantity of acetonitrile and large quantities of anhydrous ether, dried and weighed. The yield was 350 mg lithium salt of the 9- dicyanomethylene-Z,4,7-trinitrofluorene ion radical.
  • a material in order to prepare an electrode selective to tetraphenylarsonium ions a material can be prepared as follows. 2 g tetraphenylarsoniumchloride was dissolved in a small quantity of absolute ethanol and anhydrous ether was added to precipitate the tetraphenylarsonium chloride. The precipitate was filtered off, washed well with anhydrous ether and the procedure was repeated once more. The yield was then L67 g purified tetraphenylarsonium chloride.
  • An ion-selective electrode for the analysis of the concentration of inorganic, organic and metal-organic ions in a solution comprising an electrically insulating electrode holder, an electroactive plate in said electrode holder, and an electric conductor connected to said electroactive plate, characterized in that the electroactive plate consists of a salt in which one ion is a radical-ion possessing an electron which is not spinpaired.
  • An electrode as claimed in claim 1 wherein said one ion of the radical-ion salt has the structure in which X is S, N, C or O, and the other X's may be H. CH C H C;,H,, or another aliphatic carbon chain, OCH;,. OC H or another alkoxy group, C H Cl, Br, I, or F.
  • X may be H. CH C H C H or another aliphatic carbon chain, OCH OC- H or another alkoxy group, C H Cl. Br, I, or F.
  • An electrode as claimed in claim 1 wherein said one ion of the radical-ion salt has the structure 13.
  • An electrode as claimed in claim 1 wherein said one ion of the radical-ion salt has the structure in which R is an alkyl group.
  • electroactive plate consists of a mixture of at least two radical-ion salts.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
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US00264390A 1971-06-17 1972-06-19 Ion-selective electrode Expired - Lifetime US3855097A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4116796A (en) * 1975-04-23 1978-09-26 Radelkis Elektrokemiai Muszergyarto Szovetkezet Selective halide and sulfide sensitive electrodes
WO1991010900A1 (en) * 1990-01-22 1991-07-25 Mallinckrodt Sensor Systems, Inc. Polarographic chemical sensor with external reference electrode
NL1014256C2 (nl) * 2000-02-01 2001-08-14 Hydrion B V Meetinstrument geschikt voor het meten van kationen of anionen en membraam als onderdeel van het meetinstrument.
US20050129575A1 (en) * 2003-11-12 2005-06-16 Chemtronix Inc. Heavy metals monitoring apparatus
CN103940882A (zh) * 2014-04-18 2014-07-23 上海师范大学 一种水样中痕量铜离子传感器及构建方法
CN104155351A (zh) * 2014-03-24 2014-11-19 东力（南通）化工有限公司 一种测量土壤、植物、农药、饲料、食品、水样品中微量亚硝酸根和硝酸根离子含量的电位法
US11015445B2 (en) 2016-10-03 2021-05-25 Halliburton Energy Services, Inc. Electrochemical sensing using optical systems with electrochemical probes for wellbore applications

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA993048A (en) * 1973-01-15 1976-07-13 Gerardus W.S. Van Osch Electrochemical electrode compositions and assembly

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2930967A (en) * 1953-12-29 1960-03-29 Gulf Research Development Co Method and apparatus for logging drilling fluid
US3438886A (en) * 1966-03-14 1969-04-15 Orion Research Organic liquid ion-exchanger electrode
US3446726A (en) * 1963-07-22 1969-05-27 Metrimpex Magyar Mueszeripari Heterogeneous selective membranes
US3591464A (en) * 1968-09-06 1971-07-06 Orion Research Method and apparatus for detecting ionic activity
US3691047A (en) * 1970-01-08 1972-09-12 New England Merchants National Membrane electrode
US3753887A (en) * 1969-06-04 1973-08-21 Hydronautics Alkali metal specific measuring electrode

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2930967A (en) * 1953-12-29 1960-03-29 Gulf Research Development Co Method and apparatus for logging drilling fluid
US3446726A (en) * 1963-07-22 1969-05-27 Metrimpex Magyar Mueszeripari Heterogeneous selective membranes
US3438886A (en) * 1966-03-14 1969-04-15 Orion Research Organic liquid ion-exchanger electrode
US3591464A (en) * 1968-09-06 1971-07-06 Orion Research Method and apparatus for detecting ionic activity
US3753887A (en) * 1969-06-04 1973-08-21 Hydronautics Alkali metal specific measuring electrode
US3691047A (en) * 1970-01-08 1972-09-12 New England Merchants National Membrane electrode

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4116796A (en) * 1975-04-23 1978-09-26 Radelkis Elektrokemiai Muszergyarto Szovetkezet Selective halide and sulfide sensitive electrodes
WO1991010900A1 (en) * 1990-01-22 1991-07-25 Mallinckrodt Sensor Systems, Inc. Polarographic chemical sensor with external reference electrode
US5078854A (en) * 1990-01-22 1992-01-07 Mallinckrodt Sensor Systems, Inc. Polarographic chemical sensor with external reference electrode
NL1014256C2 (nl) * 2000-02-01 2001-08-14 Hydrion B V Meetinstrument geschikt voor het meten van kationen of anionen en membraam als onderdeel van het meetinstrument.
WO2001057508A3 (en) * 2000-02-01 2002-03-14 Hydrion B V Measuring instrument suitable for measuring cations or anions, and membrane as part of the measuring instrument
US20050129575A1 (en) * 2003-11-12 2005-06-16 Chemtronix Inc. Heavy metals monitoring apparatus
CN104155351A (zh) * 2014-03-24 2014-11-19 东力（南通）化工有限公司 一种测量土壤、植物、农药、饲料、食品、水样品中微量亚硝酸根和硝酸根离子含量的电位法
CN103940882A (zh) * 2014-04-18 2014-07-23 上海师范大学 一种水样中痕量铜离子传感器及构建方法
US11015445B2 (en) 2016-10-03 2021-05-25 Halliburton Energy Services, Inc. Electrochemical sensing using optical systems with electrochemical probes for wellbore applications

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SE374818B (enrdf_load_stackoverflow) 1975-03-17
DE2229379A1 (de) 1972-12-21

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