Potentiometric titration of chlorine and its oxy compounds in water

Potentiometric titrations at constant current with identical platinum electrodes are applied to mixtures of chlorine, chlorine dioxide and chlorite. The procedure is compared with the common amperometric method. Chlorine can be titrated with phenylarsine oxide at pH 7 even in mixtures with chlorine dioxide and chlorite, and three-component mixtures can be resolved by titrations at pH 2 and 7 with and without iodide addition. The behavior of chlorine and chlorite mixtures can be characterized by appropriate titrations.     

Potentiometric study of reaction between tetrabutylammonium periodate and phenothiazine in chloroform; application to the analysis of phenothiazine derivatives

The reaction between tetrabutylammonium periodate and phenothiazine in the presence of the strong acids in chloroform was studied by potentiometry and the reaction pathways were determined. The oxidimetric titration conditions of phenothiazine derivatives using a standardized chloroform solution of tetrabutylammonium periodate were optimized and a potentiometric detection of end points was utilized. The relative standard deviation for the determination of 5 mg phenothiazines was obtained about 1-1.5%. The method was applied for the determination of phenothiazines in various pharmaceutical preparations after extraction into chloroform.     

Potentiometric titration of plutonium

In the potentiometric titration of plutonium(III), it has been customary to take the equivalence point as the inflection point on a plot of potential vs. volume of titrant.¹ That the stoichiometric end point corresponds to the inflection point does not seem to have been theoretically demonstrated, however. The purpose of this letter is to suggest that these points may not correspond in the potentiometric titration of plutonium(III). Mound Laboratory is operated by Monsanto Research Corporation for USERDA under contract No. EY-76-C-04-0053.     

Potentiometric titration of lignosulfonic acids

The conditions of potentiometric titration of lignosulfonic acids allowing quantitative determination of strongly and weakly acidic functional groups in lignosulfonates were determined.     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Potentiometric titration of metal ions in ethanol

The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented.     

Thermal analysis of pharmaceutical compounds

The thermal behaviour of some antiallergic drugs belonging to different groups of antihistaminics, such as phenyltoloxamine, chlorpromazine, clemizole and meclozine was examined. Thermogravimetry, derivative thermogravimetry and differential thermal analysis curves were used for the elucidation of the mechanisms of thermal decomposition. The melting temperatures of the compounds and their thermal stabilities were determined. The stability was found to decrease in the order: clemizole > chlorpromazine > meclozine > phenyltoloxamine.The kinetic parameters of the thermal reactions were calculated and their values are in accordance with the results obtained, especially those of the stability.Infrared spectroscopic analysis of the compounds together with their thermal decomposition products was performed in order to establish the possible sites of decomposition.

---

Zusammenfassung Das thermische Verhalten einiger, verschiedener Antihistaminika angehörender antiallergetischer Arzneimittel, wie Phenyltoloxamin, Chlorpromazin, Clemizol und Meclozin wurde untersucht. Die Methoden der Thermogravimetrie, derivativen Thermogravimetrie und Differentialthermoanalyse wurden zur Klärung des Mechanismus der thermischen Zersetzung eingesetzt. Die Schmelztemperaturen der Verbindungen und ihre Thermostabilität wurden bestimmt. Es zeigte sich, dass die Stabilität in der Reihenfolge Clemizol > Chlorpromazin > Meclozin > Phenyltoloxamin abnimmt.Die kinetischen Parameter der thermischen Reaktionen wurden berechnet und ihre Werte, besonders die der Stabilität, sind in Übereinstimmung mit den erhaltenen Ergebnissen.Die infrarotspektroskopische Analyse der Verbindungen erfolgte zusammen mit der ihrer thermischen Zersetzungsprodukte um die möglichen Zerfallsbereiche zu ermitteln.

---

Résumé On a étudié le comportement thermique de quelques médicaments antiallergiques appartenant aux différents groupes des antihistaminiques, comme la phényltoloxamine, la chlorpromazine, la clémizole et la méclozine. On s'est servi des courbes thermogravimétriques, de leurs dérivées ainsi que des courbes d'analyse thermique différentielle pour élucider le mécanisme de la décomposition thermique. On a déterminé les températures de fusion et la stabilité thermique des composés. On a trouvé que la stabilité diminue dans l'ordre suivant: clémizole > chlorpromazine > méclozine > phényltoloxamine.On a calculé les paramètres cinétiques des réactions thermiques; leurs valeurs, en particulier celles de la stabilité, sont en accord avec les résultats obtenus.Les composés de départ et leurs produits de décomposition thermique ont été examinés par spectroscopie infrarouge afin de trouver les sites possibles de décomposition.

---

, : , , . , . . , > > > . , . , , .

     

Thermal analysis of pharmaceutical compounds

Fourteen sulphonamides have been thermally analyzed using thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA). Their thermal reactions and stabilities have been thoroughly studied. It was found that the sulphonamides are first transformed into sulphanilamide. The melting points of these sulphonamides have been determined through their DTA curves and by the Kofler microscope, the results agreeing with those reported in the literature. The amount of water of crystallization has been calculated from the TG and DTG curves. Analysis of mixtures of some sulphonamides has been achieved by thermal analysis and by thin-layer chromatography using different solvent systems.

---

Zusammenfassung Vierzehn Sulfonamide wurden unter Anwendung der Thermogravimetrie (TG), der derivativen Thermogravimetrie (DTG) und der Differentialthermoanalyse (DTA) thermisch analysiert. Die thermischen Reaktionen und Stabilitäten wurden untersucht. Es zeigte sich, daß die Sulfonamide zuerst in Sulfanilamide umgewandelt werden. Die Schmelzpunkte der Sulfonamide wurden über ihre DTA-Kurven und mit dem Kofler-Mikroskop bestimmt, die Ergebnisse stimmten mit den in der Literatur angegebenen überein. Die Menge des Kristallwassers wurde aus den TG- und DTG-Kurven berechnet. Die Analyse von zwei, drei und vier Sulfonamiden wurde durch Thermische Analyse und Dünnschichtchromatographie unter Anwendung verschiedener Lösungsmittelsysteme durchgeführt.

---

Résumé Quatorze sulfonamides ont été examinés par thermogravimétrie (TG), thermogravimétrie différentielle (TGD) et analyse thermique différentielle (ATD). Leurs réactions thermiques et leurs stabilités ont été étudées d'une manière approfondie. On a trouvé que les sulfonamides se transforment d'abord en sulfanilamides. Les points de fusion des sulfonamides ont été déterminés à partir de leurs courbes ATD et avec le microscope Kofler; les résultats ont concordé avec ceux de la littérature. La teneur en eau de cristallisation a été calculée à partir des courbes TG et TGD. L'analyse de deux, trois et quatre sulfonamides a été effectuée par analyse thermique et Chromatographie en couches minces avec différents solvants.

---

(), () () . . , . - . . - -, . , , .

     

Thermal analysis of pharmaceutical compounds

Some sulphonamides are evaluated by means of thermal analysis. Use is made of their characteristic endothermic DTA peaks (melting peaks), where the area changes linearly with variations in the amount of sulphonamides. The method is suitable for the determination of 30–100 mg of sulphathiazole, sulphisomidine, sulphaguanidine, sulphacetamide sodium and sulphamethoxypyridazine with reasonable accuracy. As for sulphisoxazole, two peaks are used for its determination: an endothermic one to determine 30–100 mg, and an exothermic one to determine 6–30 mg.

---

Zusammenfassung Einige Sulphonamide wurden durch thermische Analyse bestimmt, wobei von der linearen Abhängigkeit der Fläche der charakteristischen endothermen DTA-Peaks (Schmelzpeaks) von der Menge der Sulphonamide Gebrauch gemacht wurde. Mit der Methode können 30–100 mg Sulphathiazol, Sulphisoimidin, Sulphaguanidin, Natrium-Sulphacetamid und Sulphamethoxypyridazin mit ausreichender Genauigkeit bestimmt werden. Bei der Bestimmung von Sulphisooxazol wurde ein endothermer Peak für Mengen von 30–100 mg und ein exothermer für geringere Mengen von 6–30 mg herangezogen.

---

. - ( ), . 30–100 , , , . , — 30 100 , — 6 30 .

     

Determination of the drug content of pharmaceuticals containing phenothiazine compounds by triangle programmed flow titration

Summary A flow-through triangle programmed coulometric titration technique is worked out for the determination of phenothiazine compounds. The oxidation reaction of phenothiazines with hypobromite ion served as titration reaction. A biamperometric detector cell has been used for following the titration process. The titration technique has been used for the determination of the drug content (average and individual) of chlorpromazine, promethazine, diethazine and trifluoperazine in pharmaceutical preparations. The relative standard deviation was in the range of 2.0 to 3.5%.

---

Bestimmung des Wirkstoffgehaltes von Phenothiazin-haltigen Pharmazeutica mit Hilfe einer Dreieck-programmierten Durchflu\-Titration

     

Coulometric titration of organic and pharmaceutical compounds with electrogenerated gold(III)

Summary Electrogenerated AuCl₄– in 0.02M HCl is used to titrate hydroquinone, ascorbic acid, phenylhydrazine, phenelzine sulphate and phenylsemicarbazide, with biamperometric end-point detection. Titration recoveries are reported and compared with results of coulometry with ceric sulphate oxidation. With less than 1 mg of sample, successive titrations can be performed in the same solution, in contrast to coulometry with ceric sulphate. Phenelzine sulphate reacts stoichiometrically, as opposed to its reactions with stronger oxidizing agents.

---

Zusammenfassung An der Elektrode entwickeltes AuCl₄– in 0,02M HCl wurde für die Titration von Hydrochinon, Ascorbinsäure, Phenylhydrazin, Phenelzinsulfat und Phenylsemicarbazid mit biamperometrischer Endpunktanzeige verwendet. Die Ergebnisse wurden mitgeteilt und mit den Resultaten der Coulometrie mit Cersulfatoxydation verglichen. Im Gegensatz dazu können mit weniger als 1 mg Probe in derselben Lösung Folgetitrationen durchgeführt werden. Abweichend von seinem Verhalten gegenüber stärkeren Oxydationsmitteln reagiert Phenelzinsulfat stöchiometrisch.

     

Potentiometric and coulometric titration of 2-thiobarbituric acid

A new method for the determination of 2-thiobarbituric acid, using its reaction with iodine in an alkaline medium is presented. In the volumetric titration with potentiometric end-point detection, the determinability range is 10-400 micromol (1.4-58 mg). In coulometric titration using the biamperometric end-point detection, 0.1-20 micromol (1.4 x 10(-2)-2.9 mg) of 2-thiobarbituric acid was successfully determined.     

Potentiometric titration of permanganate with resacetophenone oxime

Milligram amounts of permanganate can be titrated with resacetophenone oxime (4-acetylresorcinol oxime) as a reducing titrant in the presence of phosphoric acid (0.5 M). The stoichiometry between permanganate and the oxime is 3:1 (MnO₄^-:oxime). The titration is successful in the presence of large amounts of dichromate or vanadate or moderate amounts of cerium(IV).     

Raman spectra of phenothiazine and some pharmaceutical derivatives

The laser-Raman spectra of several phenothiazines in the region 600-1600 cm(-1) are reported. The major bands are assigned to ring modes or to vibrations of the alkyl side-chains.     

Potentiometric titration of heterocyclic nitrogen bases in non-aqueous media

Pyridine, quinoline, isoquinoline, acridine, alpha-picoline, beta-picoline, gamma-picoline and 2,6-lutidine have been titrated potentio-metrically (calomel and glass electrodes), with chlorosulphonic acid in methyl ethyl ketone-acetic acid (1:1) medium, with an error of less than 1%.     

Potentiometric titration of gold in ores with potassium iodide

Summary A direct potentiometric titration method for the determination of gold in ores and alloys is described. It is based on the reduction of Au(III) with iodide ions yielding accurate and reproducible results. Detection limit and sensitivity were 0.06 and 0.032 mg/l Au, respectively. The linear response range was between 0.1 and 120 mg/l Au. The method can be used for the routine assay of gold in different kind of samples.     

Capillary electrochromatography of basic compounds in pharmaceutical analysis

Capillary electrochromatography (CEC) shows promising results in the separation of basic drugs. Traditional reversed-phase systems, with or without amine additives to the mobile phase to improve peak shapes, are the most commonly employed. Alternative useful stationary phases, such as strong cation exchangers and polymer-based continuous beds, are also discussed, as are methods to improve sensitivity by sample preconcentration. So far, studies performed on CEC have mainly been fundamental, but the technique is rapidly maturing and has many potential applications in the pharmaceutical field.     

Multi-residue analysis of pharmaceutical compounds in aqueous samples

Pharmaceutical compounds are nowadays an emerging group of organic pollutants in aquatic systems. Several methodologies have already been published to measure these pollutants in the environment, showing the difficulties to take into account the various compounds belonging to numerous therapeutical and chemical groups. In order to develop environmental monitoring, there is a need for a less costly and time-consuming multi-component procedure. The work presented here deals with the development of an extraction procedure which enables the measurement of a wide spectrum of pharmaceuticals at trace levels (ng 1(-1)) with quite simple equipment (i.e. GC-MS with single quadruple as analyzer). The analyzed compounds comprise anti-inflammatories, antidepressants and hypolipidic drugs. The reliability and sensitivity have been tested on 18 different compounds (7 basic compounds and 11 acidic drugs) extracted simultaneously and analyzed by GC-MS. The optimized procedure has been successfully applied to the analysis of wastewaters, surface waters and drinking waters from the following areas: first the Cortiou rocky inlet, in the Mediterranean Sea (South coast of France), highly impacted by the Marseilles wastewater treatment plant effluent and secondly the Hérault watershed by studying drinking water, surface water and wastewater. In both cases, the level of pharmaceuticals was totally unknown. Results obtained have demonstrated the suitability of the method for multi-residue analysis of different types of water matrices.