Microtitration of various anions with quaternary ammonium halides using solid-state electrodes

Many solid-state electrodes were found to respond as endpoint detectors in the potentiometric titration of large inorganic and organic anions with quaternary ammonium halides. The best response was obtained with the iodide and cyanide electrodes although practically any electrode can function as endpoint sensor. The titrants were hexadecylpyridinium chloride and hexadecyltrimethylammonium chloride; hexadecyltrimethylammonium bromide and Hyamine 1622 may also be used. Some inorganic anions thus titratable are

perrhenate, persulfate, ferricyanide, hexafluorophosphate, and hexachloroplatinate. Examples of organic anions titratable are nitroform, tetraphenylborate, cyanotriphenylborate, picrate, long-chain sulfates and sulfonates, and some soaps. The reverse titration of quaternary ammonium halides vs dodecylsulfate is also feasible. Some titrations are feasible in a partially nonaqueous medium.     

Analytical applications of quaternary ammonium halides using ion-selective electrodes: A review

Summary The analytical applications of quaternary ammonium halides are reviewed. These compounds are used as titrants in the potentiometric determination of a variety of inorganic and organic anions including soaps and surfactants. Various liquid-membrane electrodes such as the perchlorate, fluoroborate, nitrate, and calcium electrodes may be used as sensors and, in some cases, solid-state electrodes such as the cyanide (iodide) electrode. The most important titrants are cetyltrimethylammonium bromide and chloride and cetylpyridinium chloride.

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Analytische Anwendungen von quaternären Ammoniumhalogeniden mit Hilfe von ionen-selektiven Elektroden. Ein Überblick

Zusammenfassung Quaternäre Ammoniumhalogenide werden als Titrationsmittel bei der potentiometrischen Bestimmung vieler anorganischer und organischer Anionen, einschließlich von Seifen und oberflächenaktiven Substanzen, verwendet. Verschiedenartige Flüssig-Membran-Elektroden (Perchlorat-, Fluorborat-, Nitrat- und Calciumelektroden) können als Sensoren benutzt werden. Auch Fest-Elektroden (Cyanid, Iodid) kommen in bestimmten Fällen zum Einsatz. Die wichtigsten Titranten sind Cetyltrimethylammoniumbromid und -chlorid sowie Cetylpyridiniumchlorid.

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Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48

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Parts of this paper were presented at the Anorganisch-Chemisches Institut I der Universität, Frankfurt/Main, on April 23, 1981     

New Ion‐Pair Based All‐Solid‐State Surfactant Sensitive Sensor for Potentiometric Determination of Cationic Surfactants

Cationic surfactants of different types were determined using a few potentiometric sensors based on ion‐pair complexes (dodecyldimethylbenzylammonium dodecylsulfate, dodecylmethylbenzylammonium dodecylbenzensulfonate, tetrahexadecylammonium dodecylsulfate and Hyamine (benzethonium dodecylsulfate)) as sensing materials. The response of the all‐solid state surfactant sensitive electrode based on a Teflonized graphite conducting substrate, coated with a PVC membrane containing sensing material, was investigated in the solutions of Hyamine and hexadecyltrimethylammonium ion in the concentration range from 1 μM to 10 mM. Potentiometric surfactant cation titration has been performed using sodium dodecylsulfate as titrant and an ion‐pair‐based surfactant sensitive electrode as a potentiometric indicator. Several commercial surfactant products have also been titrated and the results were compared with those obtained with two‐phase standard titration method.     

Potentiometric titration of organic cations with sodium tetraphenylborate and a liquid-membrane tetraphenylborate ion-selective electrode

Simple potentiometric titrations are described for the determination of various organic cations (usually 5–25 μ mol) with 0.01 M sodium tetraphenylborate. A liquid-membrane electrode with tetrapentylammonium tetraphenyiborate dissolved in 4-nitro-m-xylene as liquid ion-exchanger is used successfully in the semi-automatic titration of quaternary ammonium compounds, cationic surfactants, alkaloids and other substances of pharmaceutical importance which are precipitated by tetraphenyiborate. Analysis of pharmaceutical preparations gave satisfactory results.     

Determination of quaternary ammonium compounds by potentiometric titration with an ionic surfactant electrode: single-laboratory validation

A potentiometric titration for determining the quaternary ammonium compounds (QAC) commonly found in antimicrobial products was validated by a single laboratory. Traditionally, QACs were determined by using a biphasic (chloroform and water) manual titration procedure. Because of safety considerations regarding chloroform, as well as the subjectivity of color indicator-based manual titration determinations, an automatic potentiometric titration procedure was tested with quaternary nitrogen product formulations. By using the Metrohm Titrando system coupled with an ionic surfactant electrode and an Ag/AgCl reference electrode, titrations were performed with various QAC-containing formulation products/matrixes; a standard sodium lauryl sulfate solution was used as the titrant. Results for the products tested are sufficiently reproducible and accurate for the purpose of regulatory product enforcement. The robustness of the method was measured by varying pH levels, as well as by comparing buffered versus unbuffered titration systems. A quantitation range of 1-1000 ppm quaternary nitrogen was established. Eight commercially available antimicrobial products covering a variety of matrixes were assayed; the results obtained were comparable to those obtained by the manual titration method. Recoveries of 94 to 104% were obtained for spiked samples.     

Potentiometric titration of organic cations precipitated by tetraphenylborate

Summary Sodium tetraphenylborate has been used for the potentiometric precipitation titration of some water-soluble organic cations, mostly those containing a quaternary ammonium group. Emf's were monitored with a fluoroborate ion-selective indicator electrode and a double-junction reference electrode. Other liquid-membrane electrodes, such as the perchlorate and nitrate, also respond to the cations investigated. The solid-state cyanide electrode responds to those cations yielding potentiometric breaks of > 70 mV with the fluoroborate electrode. The following compounds were examined: procaine, diphenhydramine, chlorpheniramine, methylene blue, dimethyl yellow, benzidine, pyridine, acetylmethylcholine, thiamine.This paper was presented at the International Symposium on Electroanalysis in Cardiff, England, on April 13, 1981     

PVC膜修饰电极上零电流示波电位滴定法测定硼的研究

以氯化十六烷基吡啶（ＣＰＣ）和氟硼酸钠形成的离子缔合物为活性物质，制成ＰＶＣ膜涂层石墨电极，提出了一个快速测定硼的零电流示波电位滴定法。以ＣＰＣ为滴定剂，用ＰＶＣ膜电极为指示电极，甘汞电极为参比电极，利用阴极射线示波器荧光屏上荧光点的突然位移来指示ＣＰＣ滴定硼的终点，具有灵敏、准确、快速等特点，用该法测定玻璃中的硼，结果良好。     

Plastic membrane ion-selective electrode for the determination of denatonium benzoate (Bitrex).

A poly(vinyl chloride) matrix membrane ion-selective electrode for the determination of the denatonium ion based on the denatonium salt of tetraphenylborate is described. The response characteristics of the electrode for the denatonium ion and for several quaternary ammonium compounds were studied. The potentiometric determination of denatonium benzoate in rapeseed oil in the range 1-10 ppm agreed to within +/-5% of the spiked amounts. The application of the electrode to the titrimetric determination of several quaternary ammonium compounds using sodium tetraphenylborate as the titrant is also described.     

橙黄Ⅳ-碱性染料或季铵盐体系电势滴定曲线研究

研究了以10^-3M或10^-4M橙黄Ⅳ滴定25种碱性染料和19种季铵盐的电势滴定曲线。提出了一种估价电势滴定曲线的方法并确定了这些曲线体系的优劣次序。讨论了碱性染料和季铵盐结构对电势滴定曲线的影响。结果表明,有些曲线可用于较高灵敏度的分析,电势滴定曲线的优劣次序可为寻找阴离子选择电极的电活性物质提供途径。     

Titration of Anionic Surfactants Using a New Potentiometric Sensor

Abstract

An anionic surfactant ion selective electrode has been developed by coating the Ru?i?ka Selectrode with plasticised polyvinyl chloride containing hyaminedodecylsulfate active substance. The electrode responds to dodecylsulfate, in the range 10^?2 ? 10^?2 mol dm^?3 and has been used for potentiometric titration of micromolar amounts of dodecylsulfate with an accuracy of 0.3%. The influence of several organic and inorganic anions has been investigated.     

Comments on the potentiometric titration of halides including fluoride with a mixed titrant

An attempt was made to verify work reported by others on the potentiometric titration of halides including fluoride with a mixed titrant of silver nitrate and thorium nitrate. The platinum indicator electrode can indeed be used to monitor the titration of bromide and chloride. However, we could not verify the results reported for fluoride. There seems to be no theoretical basis on which to expect the platinum electrode to respond to changes in fluoride ion concentration.     

Potentiometric microanalysis of soaps and mixtures of soaps with anionic surfactants

Summary An attempt was made to find a method for potentiometric titration of soaps and mixtures of soaps and anionic surfactants. A liquid-membrane electrode based on bis(dimethylglyoxime)-l,10-phenanthrolinecobaltate(III) dodecyl sulphate was used. The effects of pH, ionic strength, and temperature on the titration were studied.

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Zusammenfassung Eine Methode zur potentiometrischen Titration von Seifen und Gemischen von Seifen und anionischen Schaummitteln wurde auszuarbeiten versucht. Eine Flüssigmembran-Elektrode aus Bis-(dimethylglyoxim)-l,10-phenanthrolincobaltat(III)-Dodecylsulfat wurde dazu verwendet. Die Wirkung von pH, lonenstärke und Temperatur auf die Titration wurden untersucht.

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Paper presented at the International Symposium on Microchemical Techniques, Davos, May 1977.     

Titrations using an apparatus for recording the antilogarithm of pH or pM

A titration apparatus plotting either the concentration of sample ion or the concentration of titrant ion has been tested. An antilog apparatus, converting measured e.m.f. values into concentrations is connected to ordinary titration equipment. The instrument has been tested by means of acid—base titrations (titrations of mixtures of weak acids and of a weak and a strong acid), precipitation titrations (determination of the chloride concentration in tap-water, titration of mixtures of halides), titrations with ion-selective electrodes (determination of the fluoride content of toothpaste) and complexometric titrations (determination of copper with EDTA, using mercuric ion as indicator ion and amalgamated silver rod as indicator electrode, or using a copper-selective indicator electrode). The method considerably simplifies the evaluation of the results as compared to conventional potentiometric titrations.     

Potentiometric detection of organic acids in liquid chromatography using polymeric liquid membrane electrodes incorporating macrocyclic hexaamines

Potentiometric detection employing coated-wire electrodes was applied to the determination of organic acids in liquid chromatography (LC). Poly(vinyl chloride)-based liquid membranes, incorporating lipophilic macrocyclic hexaamines as neutral ionophores were used as electrode coatings. The selectivity and sensitivity of the macrocycle-based electrodes were found to be superior to an electrode based on a lipophilic anion exchanger (a quaternary ammonium salt). Sensitive detection was obtained for the di- and tricarboxylic acids tartaric, malonic, malic, citric, fumaric, succinic, pyruvic, 2-oxoglutaric and maleic acids after separation in reversed-phase LC. Detection limits (signal/4sigmanoise=3) of 6 pmol for malonic acid and 2 pmol for maleic acid were attained. The detection was explained using a molecular recognition model. The hexaamine-based potentiometric electrodes had a 1-s response time at 1 ml min(-1) flow-rates. They were stable for at least 4 months, with an intra-electrode variation of 3.2% (n=5).     

Ti/TiO2 indicator electrodes formed by plasma electrolytic oxidation for potentiometric analysis

Ti/TiO₂ indicator electrodes were prepared by plasma electrolytic oxidation (PEO) method in the tetraborate electrolyte and were used for potentiometric indication of chemical reactions of different types and for analysis of surface and industrial wastewaters on the example of potentiometric determination of alkalinity and chloride. The electrodes formed at current densities of 0.05, 0.1, 0.15 and 0.2 A/cm² are different in composition, surface morphology and electroanalytical properties. The electrodes formed at a current density of 0.05 A/cm² exhibit the highest pH-sensitivity and generate the highest analytical signal at the equivalence point in the acid–base and precipitation titrations. The maximum analytical signal at the equivalence point, exceeding in magnitude the analytical signal, obtained by classical Pt electrode in oxidation–reduction and complexometric titrations generates PEO layers formed at a current density of 0.05 A/cm² and a platinum-modified nanoparticles. The results of the potentiometric titration of the surface and technogenic waters using as indicator Ti/TiO₂ electrodes are comparable with the conventionally used glass electrode (to determine alkalinity) and Ag electrode (to the determine chloride) and the results of visual titration. The advantage of the obtained metal oxide systems is the ability to determine two hydrochemical parameters due to their multifunctionality and opportunity to work with a single electrode. In addition, these sensors offer some analytical characteristics such as sensitivity, good reproducibility, high mechanical stability and a simple preparation procedure.     

Potentiometric response of graphite electrodes coated with modified polymer films

Graphite electrodes coated with chemically-modified polymer films are described. Several different polymers were used, including poly(acrylic acid), poly[triethyl(vinylbenzyl)ammonium chloride], poly[trihexyl(vinylbenzyl)ammonium chloride], and poly[trihexyl(vinylbenzyl)ammonium thiocyanate]. A cation-responsive electrode can be prepared from poly(acrylic acid)-coated graphite. Anion-responsive electrodes can be prepared from graphite coated with polymeric quaternary amines. In these electrodes, the ion-sensing species is irreversibly attached to the polymer (rather than physically entrapped within a polymer matrix); this factor eliminates leaching of the active component, and the addition of a plasticizer is unnecessary. A selective sensor for thiocyanate is described; it yields a Nernstian response over the concentration range 1 × 10^?1–1 × 10^?5 M sodium thiocyanate.     

Organic analysis with a new Ag(+)-selective membrane electrode

A new Ag(+)-selective membrane electrode obtained by impregnating a graphite rod (attached to the end of a Teflon tube) with the silver(I) chelate of 1-(2',3',5'-tri-O-benzoyl-beta-D-ribofuranosyl)-4-thioxo-5-methylthio-6-azauracil dissolved in chloroform gives a stable and reproducible response to silver in the 10(-1)-10(-5)M range with a slope of 60 mV/decade. A new method for determination of some beta-chlorovinyl ketones is based on use of the electrode in potentiometric titration of the chloride displaced by tertiary amines from beta-chlorovinyl ketones in forming the corresponding quaternary ammonium salts.     

Coulometric titration of salts of strong mineral acids in acetic anhydride by application of a hydrogen/palladium electrode

The application of H₂/Pd electrodes as generator and indicator electrodes is described for coulometric titrations of alkali metal halides and trivalent metal sulphates in acetic anhydride with potentiometric end-point detection. In acetic anhydride, sodium fluoride is a strong enough base to be titrated directly with H⁺ ions obtained by anodic oxidation of hydrogen dissolved in palladium. Other halides (NaCl, KCl, LiCl, KBr and NaBr) can be determined, after reaction of halides with mercury (II) acetate, by coulometric titration of the liberated base. Potentiometric end-point detection with a H₂/Pd-mercury(I) acetate electrode pair is satisfactory. Sulphates of Fe(III), Cr(III) and Al(III) are determined by back-titrating the excess of barium acetate after precipitation of barium sulphate. The errors in these determinations are < 1% for concentrations ranging from 0.001 to 0.003 M.     

The interaction of mixed surfactants with polyelectrolytes

The interactions between a linear polymer, sodium poly(2-acrylamide-2-methylpropane sulfonate), and two cationic surfactants, dodecylpyridinium chloride and tetradecylpyridinium chloride and their mixtures with different ratios, were studied by a potentiometric titration method using a surfactant-selective electrode. The ideal mixing/ideal cooperative binding model we had proposed previously was applied to successfully predict the binding isotherms of the mixed surfactant systems and the critical aggregation concentrations of the binding. The binding of surfactant mixtures to polymers is similar to the ideal mixed micelle formation and a sort of synergetic effect was found during the binding process. Received: 18 August 1998 Accepted in revised form: 6 November 1998     

Galvanic cell without liquid junction for potentiometric determination of copper

This paper describes potentiometric measurements in an integrated galvanic cell with both indicator and reference electrodes. Both electrodes are conducting polymer-based. The copper-sensitive indicator electrode is made by using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with 2-(o-arsenophenylazo)-1,8-dihydroxynaphthalene-3,6-disulphonic sodium salt (Arsenazo-I) as the electroactive substance in the film, while the reference electrode is based on PEDOT doped by 2-morpholineoethanesulfonic acid (MES). It is shown that the galvanic cell can be used for determination of copper both in non-aqueous media (where all PVC-based membranes failed) and in the presence of chloride ions, which disturb the signal of conventional copper ion-selective electrodes with solid-state membranes. It is further shown that the titration of copper ions can be successfully monitored using the described electrochemical cell.