Sodium ion-selective membrane electrode based on a new crown ether

A sodium ion-selective PVC membrane electrode based on di(o-methoxy)stilbenzo-24-crown-8 is reported. The electrode gives a near-Nernstian response in the range 9×10^?6–1×10^?2 M sodium ion and can be used in the pH range 5–8.5. Selectivity coefficients are 1.8×10^?1 (K⁺), 2.0×10^?4 (Li⁺) 2.5×10^?2 (NH⁺₄) and about 10^?4 for Mg²⁺, Ca²⁺ and Ba²⁺.     

Use of ethylene-vinyl-acetate as a new membrane matrix for calcium ion-selective electrode preparation

A new polymer matrix based membrane electrode with an ion-exchanger responding to calcium was constructed by dissolving the copolymer ethylene-vinyl-acetate together with the ion-exchanger in chloroform in the presence of a mixture of dioctylphthalate-nitrobenzene as plasticizer. The ion-exchanger used as the electroactive component was calcium didecyl phosphate in di-(n-octylphenyl) phosphonate (Orion). This electrode exhibited near-Nernstian response over the concentration range 10(-1)-4 x 10(-6)M calcium. The pH did not affect the electrode performance within the range 8-11. Response time varied from 15 to 120 sec and the lifetime exceeded six months. The membrane is subject to static charge buildup, but this is avoided by controlling the level of dryness of the membrane. Selectivity coefficients determined for both monovalent and divalent cations showed negligible interference by most of these ions. The electrode was applied successfully to the determination of calcium in commercial mineral waters.     

Determination of potassium in fatty acid methyl esters applying an ion-selective potassium electrode

An easy and inexpensive method of potassium determination in fatty acid methyl esters (FAME) applying an ion-selective potassium electrode (ISE-K) is presented. FAME are considered alternative fuel for diesel engines. Simple apparatus and procedure were developed to avoid contact of ester samples with the sensitive ISE-K membrane, which can damage the ISE membrane surface in long time operation. Using different FAME samples with a wide range of known potassium content a calibration curve was constructed. Among all samples, ISE-K satisfactory predicted potassium content in FAME as identified by the AAS reference method.     

Serum calcium and potassium determination by the split membrane ion-selective electrode technique

Results are presented for the determination by differential potentiometry of calcium and potassium in human and sheep sera, by use of a flow-through cell. The split-membrane ion-selective electrode technique has been used in conjunction with polymer membrane electrodes of the coated-wire type and the type containing an aqueous inner reference solution. The electroactive reagent is di(n-octylphenyl)phosphoric acid for calcium and valinomycin for potassium.     

双冠醚PVC膜钾电极的研究

Kimura等报道了双冠醚,庚二酸二-[3,4-(1’,4’,7’,10’,13’-五氧杂环十五-2-烯)骈苄酯](简称双冠醚A),并用作钾离子选择性电极的活性物质。朱春生等最近报道了双冠醚B的合成。本文研究了上述两种双冠醚作为电活性物质的PVC膜钾离子选择性电极,并与目前以二叔丁基二苯骈-30-冠-10为电活性物质的PVC商品钾电极作对比,实验结果说明双冠醚钾电极在测量范围,对Na~+,NH_4~+等离子的选择性系数,pH范围等方面均优于商品电极。     

Preparation and properties of a carbonate ion-selective membrane electrode

A liquid membrane ion-selective electrode has been prepared for the measurement of carbonate ion activities in solutions containing high levels of hydrogen carbonate and chloride. The electrode exhibits Nernstian response in the approximate range 1O^-2–1O^-7M carbonate, and has a fast response and low noise level under most conditions. In the physiologically important pH region, hydroxide ion does not interfere. Detailed information is given on the composition and properties of the active membrane phase.     

Analytical study of a cadmium ion-selective ceramic membrane electrode

Summary A cadmium ion-selective membrane electrode has been developed by applying a hot-pressing method. The membrane contains cadmium sulphide, silver sulphide, and copper(I)-sulphide.The best response was obtained with a membrane containing less than 30% of copper(I) sulphide and more than 5% of cadmium sulphide. The Nernstian slope was secured over an activity range of 10^–1 to 10^–6 M, and potentiometric analysis could be carried out over a concentration range of 10^–1-10^–7 M. The potentials were maintained at constant values over more than 6 months. Also, the potentials satisfied the Nernst's factor 2.303 RT/2F at the temperature range between 0 and 95°C. Among the common ions, silver, copper(II), iron(III), mercury(II), sulphide, and iodide ions interfered seriously. However, about 10–100 times of lead and bromide ions and more than 1000 times of alkali metal, alkaline earth metal, zinc, aluminium, nickel, cobalt, manganese(II), perchlorate, and nitrate ions did not interfere at all.

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Analytische Untersuchung einer cadmiumionenselektiven keramischen Membranelektrode

Zusammenfassung Die Membran wurde durch Pressen von Cd-, Ag und Cu(I)-sulfid bei 200–500°C und 3–7 t/cm² hergestellt. Die beste Ansprechempfindlichkeit ergab sich bei einem Gehalt von <30% Cu₂S und >5% CdS. Die Nernstsche Gleichung war gültig im Bereich von 10^–1–10^–6 M, der analytische Bereich war 10^–1–10^–7 M. Die Potentiale konnten mehr als 6 Monate auf einem konstanten Wert gehalten werden. Sie entsprachen dem Nernstschen Faktor, 2,303·R·T/2 F, im Temperaturbereich von 0–95°C. Erhebliche Störungen werden durch Ag⁺-, Cu²⁺-, Fe³⁺-, Hg²⁺-, S^2– und J^–-Ionen verursacht. Jedoch verursachen etwa 10–100fache Mengen von Pb²⁺- und Br^–-Ionen sowie mehr als 1000fache Mengen von Alkali-, Erdalkali-, Zn²⁺-, Al³⁺-, Ni²⁺-, Co²⁺-, Mn²⁺-, ClO₄ ^–- und NO₃ ^–-Ionen keine Störungen.

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The authors thank Dr. S. Kisaka, Dr. K. Sugihara, Dr. S. Hayakawa and Dr. S. Mori for their encouragement in this work.     

Aromatic sulphonate ion-selective electrode membrane with crystal violet as ion-exchange site

Four triphenylmethane derivatives (cations) and a high molecular-weight quaternary ammonium ion were used as the ion-exchange site in the liquid membranes of electrodes responsive to aromatic sulphonate ions, such as benzenesulphonate and alpha-naphthalenesulphonate. The nitrobenzene or 1,2-dichloroethane membrane containing the Crystal Violet-aromatic sulphonate pair had good sensitivity, showing an approximately Nernstian response down to 10(-4)M sulphonate. The potential of the Crystal Violet membrane was independent of pH variation from 2.5 to 12. Chloride and sulphate ions in the aqueous sample solution did not affect the electrode potential. 1,3,6-Naphthalenetrisulphonate exerted essentially no influence on the potential of the alpha-naphthalenesulphonate electrode. The interference of the nitrate ion was relatively large. The conductivity and association of the solute species in the membrane were estimated.     

4'-picrylamino-5'-nitrobenzo-18-crown-6 as a sensing reagent in potassium ion-selective electrode membranes

Five crown ethers, namely, 4'-picrylamino-5'-nitrobenzo-18-crown-6 (I), dibenzo-18-crown-6 (III), dibenzo-30-crown-10 (IV), dicyclohexano-18-crown-6 (V) and bis-[(benzo-15-crown-5)-15-ylmethyl pimelate] (VI) have been compared with valinomycin (II) for their role as potassium ion-sensors in PVC matrix membrane ion-selective electrodes (ISEs). Sensor I was found to be the best, but fell short of the high quality of the well established sensor II (valinomycin) in terms of selectivity towards potassium over sodium and ammonium. Nevertheless, electrodes made from membranes containing sensor I, 2-nitrophenyl octyl ether (NPOE) or 2-nitrophenyl phenyl ether and potassium tetra-p-chloro-phenylborate (anion excluder) in PVC were of long lifetimes. The loss of slope of the ISEs is linked to small falls in the electrical resistance of the ISE membranes; this being associated with leaching of sensor and solvent mediator from the membranes into test or storage solutions. No chromatographic evidence was found of anion excluder being leached.     

Use of an ion-selective membrane electrode for the determination of the active components in intestopan

The conditions for the determination of broxyquinoline and brobenzoxaldine, the active components of "Intestopan", by use of ion-selective membrane electrodes are described. Broxyquinoline is determined directly through precipitation with CuSO(4), and brobenzoxaldine is first hydrolysed in alkaline solution and the product precipitated with CuSO(4). In both cases the CuSO(4) in excess is determined by potentiometric titration at pH 5.6 with EDTA, a Cu(2+)-selective electrode being used for end-point detection.     

Potentiometric studies on thioacetamide by means of a sulphide ion-selective membrane electrode

The sulphide ion-selective electrode has been found to be applicable to the determination of thioacetamide in the concentration range of 10^-1–10^-3 M by direct potentiometry and titration with silver nitrate. The effects of the acid and alkali content of the solutions on the titration reaction have been studied. In alkaline and slightly acidic solutions the product of the reaction is silver sulphide; in solutions in which the acid concentration exceeds 0.5 M, a precipitate of silver thioacetamide is formed. If the alkali concentration of the solution is lower than that corresponding to the amount of acid formed during the titration, another potential jump occurs before the end-point owing to the decrease of sulphide'concentration governed by hydrolysis.     

A salicylate ion-selective membrane electrode based on aliquat 336s and the assay of acetylsalicylic acid

The construction and the general performance of a salicylate ion-selective PVC membrane electrode based on Aliquat 336S are described. The electrode is applied for the assay of aspirin in tablets after hydrolysis of acetylsalicylic acid to salicylate. The method has the advantage of simplicity and speed compared to standard procedures.     

Novel sulfate ion-selective polymeric membrane electrode based on a derivative of pyrilium perchlorate

A sulfate ion-selective PVC membrane sensor based on 4-(4-bromophenyl)-2,6-diphenylpyrilium perchlorate (BDPP) as a novel sensing material is successfully developed. The electrode shows a good selectivity for sulfate ion with respect to common organic and inorganic anions. The sensor exhibits a good linear response with slope of -28.9+/-0.5 mV per decade over the concentration range of 1.0x10(-6)-1.0x10(-2) M, and a detection limit of 8.0x10(-7) M of SO(4)(2-) ions. The electrode response is independent of pH in the range of 4.0-9.0. The proposed sensor was applied as an indicator electrode in potentiometric titration of sulfate and barium ions, and to the determination of zinc in zinc sulfate tablets.     

In vivo measurements with a potassium ion-selective microelectrode based on a new bis(crown ether)

Potassium ion-selective microelectrodes with a tip diameter of 10 μm are described. The ionophore used is 2,2′-bis[3,4-(15-crown-5)-2-nitrophenylcarbamoxymethyl] tetradecane in a conventional mixture with sodium tetraphenylborate, an ether and PVC. The electrode provides Nernstian response over the range 10^?5?10^?1 M potassium activity. Its selectivity is shown to be similar to that of a valinomycin-based microelectrode. After the electrode has aged for 24 h, the 95% response time at the 10^?3 M potassium ion level is 2.0 ± 0.5 s. The applicability of the bis(crown ether) electrode for measurements in vivo is proved by monitoring the changes in potassium activity in different areas of the brain of anaesthetized rats after administration of veratrine.     

Selectrode—the universal ion-selective electrode : Part VII. A valinomycin-based potassium electrode with nonporous polymer membrane and solid-state inner reference system

A potassium electrode utilizing a solution of valinomycin in diphenylether and a porous membrane is compared with selectrodes in which the diphenylether has been replaced by a suitable plasticizer and the porous membrane support by a polymer net-work. The development of the polymer membrane allows the use of simplified selectrode construction with a “solid-state” calomel reference system; Rules for a successful choice of a suitable solvent-polymer combination are suggested and used for development of new Polyvinylchloride- and polyurethane-based membranes.     

Potentiometric studies on organic compounds containing sulphur with a sulphide ion-selective membrane electrode

Phenylthiourea and N,N-diphenylthiourea can be determined in the concentration range 10¹–10^?3M by potentiometric titration with silver nitrate solution with a sulphide ion-selective membrane electrode. The influence of the alkali and acid concentration on the course of the reactions with the silver nitrate titrant was studied. When phenylthiourea is titrated in the presence of 0.1 M sodium hydroxide, silver sulphide is precipitated, and the phenylcyanamide formed simultaneously reacts further with silver nitrate to form a silver phenylcyanamide precipitate. When N,N-diphenylthiourea is titrated under similar conditions, silver sulphide is again formed, but no cyanamide-type compound can be formed owing to the presence of the second phenyl group. In 1 M sodium hydroxide both compounds studied react with two equivalents of silver to give silver sulphide and phenylurea or diphenylurea, respectively. In the presence of nitric acid both compounds react similarly with silver nitrate. Two molecules of the compounds react with one molecule of silver nitrate to give a white precipitate.     

低检出限聚合物膜镉离子选择性电极的研制及应用

基于痕量电位分析原理,研制出了一种新型的聚合物膜镉离子选择性电极.通过优化电极内充液组成及聚合物膜组分,电极在10-8～10-4mol/L镉浓度范围内呈现良好的能斯特响应,响应斜率为24.9 mV/dec.,检出限可达5.9nmol/L.该电极应用于实际湖水样品中镉含量的检测,结果与ICP-MS法数据较为吻合.     

中性载体可咯化合物应用于银离子电位传感器的研究

研制了一种以5,10,15-三(五氟苯基)可咯[H_3(tpfc)]为活性组分物质、以邻硝基苯辛醚o-NPOE为增塑剂、以四苯硼钠为亲脂性大阴离子添加剂的PVC膜电极(4种物质的质量比为3:3:62:32),电极能斯特斜率为54.8 mV/decade、工作浓度范围为5.1×10~(-6)～0.1 mol/L,pH为4.0～8.0,响应时间不超过30 s,该电极对银离子能抵抗来自Hg~(2+)、Pb~(2+)等离子干扰,表现出较高的选择性.这种传感器可用于对实际矿石样品进行检测.     

Construction and evaluation of a novel In(III) liquid ion-selective membrane electrode

A liquid ion-selective membrane electrode containing a chloroform-acetonitrile (10:1) solution of the complex of In(III) with 1-benzyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and diphenylguanidine is described. The basic electrode performance characteristics were evaluated according to IUPAC recommendations. The slope of the calibration graph (electrode potential v. concentration) was 18.7 mV (pIn)(-1) in the pIn range 4.5-1 (pH 6). Direct potentiometric determination of In(III) showed an average recovery of 99.1% with a standard deviation of 1.2%. The method is recommended for the precise direct potentiometric assay of In(III) in metals and minerals without a prior separation.