Polarography of arsenic

The polarographic behaviour of arsenic in various media is reviewed with particular emphasis on the mechanisms of the electrode reactions and on the use of polarographic methods for the determination of the element.     

Sine-wave polarographic determination of zirconium or niobium in aqueous media

The sine-wave polarographic determination of zirconium in aqueous media was investigated using solutions which were 0.55 – 5.5·10^-3M in zirconyl chloride and 1 M in potassium chloride and had been adjusted to pH 2.0 with hydrochloric acid. It was possible to determine zirconium in the concentration range of 0.05 to 0.4 mg per ml. The sine-wave polarographic behavior of zirconium in aqueous solutions in the pH range 2–3 is discussed. The sine-wave polarographic determination of niobium in aqueous media was investigated using concentrated sulfuric acid containing 5 to 0.1 mg of niobium per ml in a supporting electrolyte of citric acid; the determination of niobium was possible down to 0.1 mg of niobium per ml of concentrated sulfuric acid although the D.C. polarographic method was impractical for the determination of less than 0.5 mg of niobium per ml.     

Polagraphic determination of some metal diethyldithiocarbamates

The polarographic behaviour of Cu, Pb, Zn, Mn, Cd, Ni and Bi diethyldithiocarbamates in benzene-methanol media was examined. A separation method was developed which allowed polarographic determination of all of these complexes without mutual interferences. Good precision and accuracy were obtained in the analysis of artificial mixtures and standard samples.     

Polarography of metal-gallic complexes

The polarographic behavior of metal ions in perchlorate media containing gallic acid is described. Tungsten(VI) forms a complex with gallic acid which yields a single wave in these media, useful in the polarographic determination of tungsten. Evidence for complexation of chromium(III), copper(II), iron(III), molybdenum(VI), uranium(VI), vanadium(V), tungsten(VI), praseodymium(III), samarium(III), neodymium(III) and gadolinium(III) is obtained and the behavior of these metal ions is summarized.     

The use of redox reactions in analysis of dyes and dye intermediates: X. Polarographic and constant-potential coulometric determination of 4,4′-dihydroxyazobenzene and 4-nitro-4′-hydroxyazobenzene

Conditions have been found for a polarographic and constant-potential coulometric determination of 4.4′-dihydroxyazobenzene and 4-nitro-4′-hydroxyazobenzene in buffered media.     

AC polarographic reduction of biguanides

Biguanides present ac polarographic activity in buffered media. At acid pH the reduction process is controlled by diffusion. The equation of waves and measurement criteria are discussed.     

Polarographic Determination of Aztreonam

Abstract

The polarographic behaviour of Aztreonam is studied. In acid media, at pH values lower than 6, in differential pulse polarography a peak is observed at a potential close to ? 0.6 volts. The optimum conditions for the polarographic signal are established and the different parameters affecting the electrochemical process are studied. The relationship between peak intensity and the concentration of Aztreonam is linear for concentrations lower than 1.0 ? 10^?5 M, the detection limit being 1.4 × 10^?8 M It was observed that the presence of 1-arginine does not affect the polarographic signal of Aztreonam to any significant extent.     

The Polarographic Behaviour of Bromate Ions in Buffered and Unbuffered Solutions and the Effect of Surface Active Substances

The polarographic behaviour of bromate ions in buffered and unbuffered solutions has been studied in the absence and presence of cationic, anionic and nonionic surfactants. The mechanism for the reduction in acid media is discussed. The adsorption effects of electrochemically inactive surfactants on the polarographic waves of BrO₃^? has been investigated. The values of the kinetic parameters for the electrode reaction at different pH values have been computed.     

Polarographic behaviour of 2,4-dinitrodiphenylamine in amphiprotic media

Two six-electron diffusion-controlled irreversible waves are obtained for the polarographic reduction of 2,4-dinitrodiphenylamine (DPA) in buffered and unbuffered media in all compositions of methanol-water mixtures. Based on the polarographic and coulometric data, it is suggested that each of the nitro groups is reduced to the corresponding amine in a single stepvia the diimine intermediate to give 2,4-diamino DPA as the final product. The influence of various factors such as structure of the depolariser, pH and composition of methanol on the reduction of the compound is also discussed.     

The Polarographic Determination of Tenoxicam in the Pharmaceutical Preparations

Abstract

In this study, the polarographic behaviour and the optimum polarographic conditions for the determination of TNX using DC (direct current), DP (differential pulse), SCAP (superimposed constant amplitude pulse) and SIAP (superimposed increasing amplitude pulse) polarographic techniques are described based on the reduction of enol group of the molecule on the dropping mercury electrode. The experiments were conducted in the aqueous supporting electrolyte solution containing 0.2 M KCl and 0.2 M buffer solution. Single waves were obtained at various pH values. The limiting currents were decreased and E_1/2 values were linearly shifted to more negative potentials with an increase in the pH. The system was irreversible at both the acidic and the basic media and it was adsorptional in the acidic medium and diffusional at pH 10.8. The variation in the limiting current was found to be 0.86 μA/°C. Good relations were obtained for DC, DP, SCAP and SIAP polarographic techniques at pH 10.8. The determination of TNX in pharmaceutical preparations, namely Tilcotil® tablets, containing 20 mg of TNX were tested employing DC, DP, SCAP, SIAP polarographic techniques. The results were compared to those of HPLC and the standard deviations (SD) were found to be in the range of 0.14 and 0.22 for the techniques employed for filtered and unfiltered solutions. The polarographic techniques used for the determination of TNX seem to be accurate, rapid and practical. Therefore, the suggested method may be promising in the routine analysis.

     

极谱双点滴定法测定奎宁类药物

本文提出以0.1 mol/KI、0.025％聚乙烯醇为底液,以CdCl_2标准溶液为滴定剂,用极谱双点滴定法测定奎宁。该方法具有简便、快速等优点。     

Polarographic determination of mitoxantrone in pharmaceutical preparations and biological media

An A.c. tast polarographic method for the determination of mitoxantrone in pharmaceutical preparations and biological media is described. The optimum pH for the extraction of the drug from various samples into a 4:1 mixture of chloroform-isopropanol is indicated. The effect of other parameters such as temperature, composition of supporting electrolyte and polarographic variables (drop time, a.c. voltage amplitude, voltage sweep rate) on the sensitivity and reproducibility of the method is also verified, and a simple and precise recommended method is proposed for the determination of mitoxantrone. The method is found to be applicable to the analysis of the drug in extracted phases at concentrations 5 x 10(-7) - 2.5 x 10(-5) M with a precision of about 1.5% (relative standard deviation). The limit of detection is calculated as 3.5 x 10(-7) M for both aqueous pharmaceutical preparations and biological media.     

Polarographic determination of impurities in high-purity phosphorus

Square-wave and radio-frequency polarographic techniques in phosphoric acid-potassium chloride media are applied to the simultaneous determination of copper, lead and cadmium in highpurity red phosphorus down to a level of 0.1 ppm. In addition ca. 0.01 ppm of cadmium is determined by R.F. polarography in potassium sulphate base electrolyte after cation-exchange separation.     

Polarographic study of flavonoids. Flavone,flavonol, and 3-chloroflavone

The polarographic behavior of flavone and its 3-hydroxy and 3-chloro derivatives on a dropping mercury electrode was studied. It is shown that the investigated compounds in solution are represented by two polarographically active forms in equilibrium, one of which is reduced primarily in acidic media, the other of which is reduced primarily in neutral and alkaline media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1028–1031, August, 1978.     

A polarographic and spectral study of some C- and N-nitroso compounds.

A wide range of N-nitroso compounds was investigated polarographically and spectrophotometrically. In general, the =N-N0 group is reduced in a 4-electron step in acidic media, which is most suitable for differential pulse polarographic analysis at the trace level. If the groups R and/or R' attached to the nitrosamine group are saturated entities, then the resulting differential pulse polarographic peaks are broad and of little use in the resolution of mixtures. The limit of detection is of the order of 10^-6M. If R and R' are unsaturated, the polarographic peaks are much sharper, mixtures can be resolved and the limit of detection is of the order of 10^-7M, C-Nitroso and C-nitro compounds are best determined by differential pulse polarography, because the waves are comparatively large and sharp, and because the reductions occur at relatively positive potentials where co-extractible interferences from foods, etc., will interfere to a minimal degree.     

Determination of sunset yellow and tartrazine by differential pulse polarography

A study has been made of the polarographic (DC and DPP) behaviour of the food dyes Sunset Yellow and Tartrazine in acid and alkaline media and in the absence and presence of polyvinylpyrrolidone. Methods are proposed for the determination of both dyes by DPP over a concentration range of 0.1-10 ppm. The methods have been applied to their determination in soft drinks.     

Electrochemical behavior of benzo[b][1,6]naphthyridine derivatives

The electroreduction of benzo[b][1,6]naphthyridine derivatives in anhydrous media by the polarographic method was studied. It is found that the first step of the process is the transfer of an electron to position 10 of the molecule, which is consistent with the addition of nucleophilic reagents to this particular position of the tricyclic system in question.     

Polarographic and Voltammetric Assays of Sulfonamides as α‐Oxo‐γ‐Butyrolactone Arylhydrazones

Abstract

2‐Acetylbutyrolactone was characterized as a novel reagent of analytical potential in polarographic and voltammetric analyses. It forms α‐oxo‐γ‐butyrolactone arylhydrazones through Japp‐Klingemann coupling reaction with primary arylamines. α‐Oxo‐γ‐butyrolactone arylhydrazones possess an electro‐active site (azomethine center) that displays a cathodic activity at the mercury electrode. The protonated azomethine center of α‐oxo‐γ‐butyrolactone arylhydrazones is reduced by 2e/2H⁺ reaction to the hydrazo form. The differential pulse polarographic behavior of α‐oxo‐γ‐butyrolactone arylhydrazones was investigated in aqueous media ranging from pH 2 to 10.5. In aqueous acidic solution, α‐oxo‐γ‐butyrolactone arylhydrazones were shown to adsorb on a hanging mercury drop electrode and to be amenable to determination by adsorptive stripping voltammetry. Procedures for applying the polarographic and voltammetric methods to determination of sulfadiazine and sulfamethoxazole in pharmaceutical preparations have been developed. An analogous study on sulfas‐azo derivatives of ethyl acetoacetate was also considered. Furthermore, the differential pulse voltammetric method was adopted for determination of sulfamethoxazole in spiked plasma and urine samples. The recoveries turned out to be satisfactory, showing relative standard deviations from 2.4 to 4.6%.     

Polarographic Behaviour of some Triazol Derivatives

Abstract

The polarographic behavior of some organic dyes such as nitro-benzo-triazol, amino-nitro-benzo-triazol, benzo-triazol azo thionaphthene carboxylic acid and 5-methyl imidazol 2-methyl benzo-triazol in aqueous buffered media has been studied. The results reveal that the reduction reactions occurred irreversibly under diffusion-control. The reduction mechanism of nitro-benzo-triazol and amino-nitro-benzo-triazol involve the consumption of six electrons in the form of one wave in acid and two waves in alkaline media. The electro-reduction of benzo-triazol azo thionsphthene carboxylic acid consumes four electrons. The mechanism proposed for that compound indicates that the triazol centre forms a radical as an intermediate state in alkaline medium. The reduction process of 5-methyl imidazole 2-methyl benzo-triazol contains two consumed electronic in acid media while four electrons are consumed in alkaline media.     

Electrochemical reduction behaviour of the synthetic pyrethroid insecticide cyfluthrin and its determination in formulations and environmental samples

The polarographic behaviour of cyfluthrin (CY), an α-cynoester pyrethroid, was studied using a dropping mercury electrode and hanging mercury drop electrode in methanolic Britton–Robinson (B–R) buffer of pH 2.0–12.0 with different ionic media. The nature of the electrode process was examined, the number of electrons was evaluated, and the reduction mechanism was proposed. Quantitative determination was achieved in the concentration range of 6.0?×?10^?8 to 1.15?×?10^?5?mol?dm^?3 using a differential pulse polarographic method with a lower detection limit of 2.4?×?10^?8?mol?dm^?3. The proposed method was successfully applied in the determination of CY in formulations, grains, soils, and spiked water samples.