Potentiometric determinations with the silver sulfide membrane electrode : Part I. Determination of cyanide

The possibilities of the silver sulfide membrane electrode for the determination of cyanide are described; determinations by multiple standard addition and titration have been studied, and interferences have been checked. The determination of cyanide in solutions containing various metal complexes, and the evolution method for separation of hydrogen cyanide are discussed. Automatic titration can be used for samples containing 1 p.p.m. cyanide, and the standard addition method for 1 p.p.b. cyanide.     

Potentiometric determination of sulfonamides with a silver sulfide electrode

The silver sulfide membrane electrode shows well-defined responses to several pharmaceutically important sulfonamides over the concentration range 10^-1–10^-4 M. Both direct and titrimetric determinations of sulfonamides are described and applied to pharmaceutical dosage forms.     

A self-generating third-order electrode: Part II. Analytical applications of the silver—silver sulphide electrode

Analytical applications of the silver—silver sulphide electrode are illustrated by potentiometric determinations of Cd(II) and Pb(II) ions. The stability of the electrode potential in the presence of oxidizing agents is demonstrated by various titrations with silver(I) solutions. The influence of pH on the electrode potential in pure acidic solutions is noted. The electrode used was prepared by electrolytic deposition of silver sulphide on a silver rod; after 2 years, it remained reliable, and was unaffected by light under normal laboratory conditions.     

Potentiometric monitoring of proteins: Part 1. Introduction and theory for a silver electrode

A brief survey of methods for monitoring of proteins is given, and the relative advantages and disadvantages of potentiometry are considered. A theoretical model is presented for direct potentiometric monitoring of a thiol-containing protein with a silver electrode. The model is used to indicate ways of improving the reproducibility and response of the electrode.     

Potentiometric titrations with ion-exchanging membrane electrodes : Part II. A theoretical treatment of the effect of membrane selectivity

The possible influence of the selectivity of the membrane used in an indicating electrode with potentiometric titrations was investigated by introducing some simple modifications in the calculations performed earlier. The influence of the selectivity is visible only before the equivalence point when the counter-ion is precipitated initially from the titrated solution. When the co-ion is precipitated initially, the shape of the titration curve is altered only after the equivalence point. The reliability of the determination of the equivalence point can be either advantageously or disadvantageously influenced by the selectivity, depending on the value of the selectivity coeffcient and the ratio of the diffusion coefficients.     

Potentiometric titrations with ion-exchanging membrane electrodes: Part II. Theoretical aspects of simple precipitation titrations

Titration curves were derived for potentiometric titrations with zero electric current, utilizing a membrane electrode as indicating electrode, the membrane consisting of permselective, ion-exchanging material. As a first example, calculations were made for simple precipitation titrations with only +1 or -1 charged ions present in the solution to be titrated and in the reagent. For the calculations of the membrane potentials the theory of TEORELL and MEYER and SIEVERS was used. The influence of several parameters, such as the diffusion coefficients of the ions, the capacity of the membrane and the concentration of the solutions, was examined.     

Mapping concentration profiles within the diffusion layer of an electrode: Part II. Potentiometric measurements with an ultramicroelectrode

A platinum-disk ultramicroelectrode is used to monitor electrochemical potential variations inside the steady-state diffusion layer created by a larger electrode. The experimental potential variations result from combination of a pure electrochemical component (viz., as given by the Nernst law) with a smaller ohmic drop contribution, which varies linearly with the distance from the working electrode surface so that it can be readily eliminated. From the ensuing corrected potential variations, the concentration profiles of the electroactive species present within the diffusion layer can be reconstructed by application of the Nernst law. The validity and great interest of the method are demonstrated experimentally by the study of the one-electron reversible oxidation of the Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ couple in aqueous KCl solutions. As a correlation, this demonstrates also for the first time the validity of the Nernst layer approximation. The method is then applied to examine the specific structure of the diffusion layers, which result from the involvement of a conproportionation reaction during the second reduction of tetracyanoquinodimethane (TCNQ) in DMF.     

Automated immunoassay with a silver sulfide ion-selective electrode

Antibody levels in the μg ml^-1 range are selectively and rapidly determined in an automated flow system which employs an Ag₂S membrane electrode sensor in conjunction with immobilized immunoabsorbent. Experiments with anti-benzoate antibody in the presence of excess γ-globulin or whole serum demonstrate the operating characteristics of the system in terms of selectivity, precision and dynamic response.     

Potentiometric determination of silver(I) by selective membrane electrode based on derivative of porphyrin.

The performance of silver metal complexes with meso-tetraphenylporphyrin ([H2T(4-CH3)]PP) as ionophores for ion-selective electrodes was studied. The electrode exhibited linear response with Nernstian slope of 59.2 +/- 1.0 mV per decade within the concentration range of 1.0 x 10(-7)-1.0 x 10(-1) M silver ions. The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot, was 1.0 x 10(-7) M. The response time of the electrode was < 10 s over the entire concentration range. The silver-selective electrode exhibited good selectivity for Ag(I) with respect to alkali, alkaline earth and heavy metal ions. The electrodes could be used at least three months without a considerable divergence in their potential. The electrodes are suitable for use in aqueous solutions in a wide pH range of 3.0-9.0. They were used as indicator electrodes in titration of Ag(I) with sodium iodide solution and were successfully applied to direct determination of silver in real samples.     

Conducting polymer ion sensor electrodes-III. Potentiometric sulfide ion selective electrode

A new potentiometric sensor electrode for sulfide based on conducting polymer films is introduced. The electrode is formed by electrochemically depositing a film of poly(3-methylthiophene) and poly(dibenzo-18-crown-6) onto an alloy substrate. Different methods were used for the electrode preparations. The alloy used has a low melting point, which allowed its use for manufacturing a microsize version of this electrode. The electrode response is stable for 3 days. The working temperature range for this electrode is between 10 and 40 degrees C. The linear dynamic range is 1.0x10(-7)-1.0x10(-2) M and measures total sulfide concentration over a range of pH from 1 to 13. The polymer electrode showed high selectivity for sulfide in the presence of many common interfering anions. The electrode is useful for the measurement of total sulfide in biological environments and can be manufactured in the micron scale. Therefore, it will be useful for the measurement within biofilms.     

Potentiometric studies of dithiooxamide with a sulphide-selective membrane electrode

The sulphide-selective electrode is applicable to the determination of dithiooxamide by titration with silver nitrate. The effect of the alkali content of the solutions on the reaction has been studied. The reaction products are silver sulphide, oxalic acid, and nitric acid. If the alkali concentration of the solution is lower than that equivalent to the acid formed during the titration, the amount of sulphide produced by hydrolysis decreases and the equilibrium potential is established more slowly.The determination is rapid and accurate in the presence of 1 M sodium hydroxide.     

巯基化合物的电位分析法研究

本文对用直接电位法测试巯基化合物的可行性进行了研究。发现由硫化银，硫化汞等金属难溶盐制成的膜电极对６－巯基嘌呤，高胱氨酸，１，４－二巯基苏糖经合物可产生响应，其斜率为３０－１１０ｍＶ／ｐＣ，电极响应时间，则为十几秒至十几分钏，测试结果具有较好的重现性。因此，该方法可望得到应用。文中还对有关响应机理进行了探讨。     

Electrolytic nucleation of silver on a glassy carbon electrode: Part II. Steady-state nucleation rate

The dependence of the number of nuclei on time is investigated in a wide overvoltage interval using different glassy carbon electrodes. The data for the steady-state nucleation rate are interpreted on the basis of both classical and atomistic theoretical concepts. Conclusions are drawn for the applicability of the two models of nucleation.     

Potentiometric determination of sulphate in fertilisers with cadmium sulphide membrane electrode

Summary A method is described for the determination of sulphur in fertilisers using reduction and evolution of hydrogen sulphide followed by a potentiometric titration with lead nitrate. Several procedures are tested for the destruction of the samples. The most accurate results are obtained after dissolution of the fertiliser in hydrochloric acid.

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Potentiometrische Bestimmung von Sulfat in Düngemitteln mit Hilfe der Cadmiumsulfid-Membranelektrode

Zusammenfassung Die vorgeschlagene Methode beruht auf Reduktion und Entwicklung von H₂S, gefolgt von einer potentiometrischen Titration mit Bleinitrat. Zum Aufschluß der Probe wurden verschiedene Verfahren getestet, wobei die Auflösung in verdünnter Salzsäure die besten Ergebnisse brachte.

     

Potentiometric applications of the response of a sodium-selective glass electrode to silver

The use of a sodium-sensitive glass electrode for the determination of silver ion is demonstrated.     

用氧瓶燃烧-电位滴定法测定煤中有机硫和橡胶总硫

研究了煤中有机硫和橡胶中总硫的微量测定方法,样品经氧瓶分解后所转变的ＳＯ４２－在Ｆｅ（ＣＮ）６３－／Ｆｅ（ＣＮ）６４－电对存在下用Ｐｂ２＋滴定。提出了采用Ｚｎ３［Ｆｅ（ＣＮ）６］２、微酸性溶液和低浓度Ｆｅ（ＣＮ）６４－存在下,消除磷干扰的新方法,应用于合成样品和实际样品的分析,结果满意。其回收率＞９８％,相对标准偏差＜２．３％,绝对误差＜０．１５％。     

Potentiometric studies in oxidation-reduction reactions: Oxidation with chloramine-b. indirect determinations

Chloramine-B has been used as an oxidising agent to determine indirectly potassium iodate, potassium metaperiodate, potassium, bromate, potassium dichromate, hydrogen peroxide, chloramine-T and potassium permanganate by a potentiometric method. An excess of potassium iodide added to each of the substances in an acid medium is titrated back with a standard solution of chloramine-B, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Potentiometric determination of tetraphenylborate ions with silver nitrate. Determination of silver, potassium and thallium(I)

Summary The potentiometric determination of tetraphenylborate with silver nitrate solution was investigated a) at i=0 in the presence of calomel reference electrode and silver resp. silicone rubber based halide-selective indicator electrodes and b) at i0 in the presence of silver (cathode)-calomel, silver-silver, silver-platinum, platinum-silver and graphite-silver electrode couples. An indirect method is described for the determination of potassium ions with potentiometric end-point indication. Experiments were also carried out in order to develop methods for the titration of silver, potassium and thallium(I) ions with sodium tetraphenylborate solution in the presence of anodic polarized graphite and calomel reference electrodes. The relative standard deviations were 0.38–0.49% for tetraphenylborate, 1.96% for potassium and 1.07% for thallium(I).

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Potentiometrische Bestimmung von Tetraphenylborationen mit Silbernitrat. Bestimmung von Silber, Kalium und Thallium(I)

Zusammenfassung Die Möglichkeit der potentiometrischen Bestimmung von Tetraphenylborat mit Silbernitrat wurde untersucht a) in Anwesenheit von Kalomel-Bezugselektrode und Silber- bzw. haloidselektiven Silicongummi-Indicatorelektroden bei i=0 und b) in Anwesenheit von Silber (Kathode)-Kalomel-, Silber-Silber, Silber-Platin-, Platin-Silber- und Graphit-Silber-Elektrodenpaaren bei i0. Eine Methode zur indirekten potentiometrischen Bestimmung von Kalium sowie Verfahren zur Bestimmung von Silber-, Kalium- und Thallium(I)-ionen mit Natriumtetraphenylboratlösung in Anwesenheit einer anodisch polarisierten Graphitelektrode und einer Kalomel-Referenzelektrode wurden ausgearbeitet. Die relativen Standardabweichungen betragen für Tetraphenylborat 0,38–0,49%, für Kalium und Thallium 1,96 bzw. 1,07%.