Polarographic analysis. II

Summary The polarography of hexavalent uranium in sulphuric acid solutions of different concentrations and solutions containing sodium sulphate is studied. In 0.01 M H₂SO₄ three waves are obtained corresponding to the successive reduction of U^VI to U^V, U^V to U^IV and U^IV to U^III. The second and third waves intermingle by increasing the H₂SO₄ concentration up to 0.055 M or by adding Na₂SO₄ or sulphosalicylic acid. In 0.25 M H₂SO₄ or in the presence of EDTA the second wave shifts to less negative potentials and intermingles with the first wave, forming a single wave along which reduction of U^VI gives a mixture of U^V and U^IV. The diffusion current of this wave increases up to 1 M H₂SO₄ and then decreases above this acidity. The diffusion current measured at –0.6 V is proportional to the U^VI concentration in the presence of 0.25–0.6 M H₂SO₄. This is not the case in the presence of EDTA. The proportionality is better at lower than at higher acidity.Part I: See Z. analyt. Chem.174, 4 (1960).     

Polarographic analysis. III

Summary Reduction of U^VI in H₃PO₄ solution passes to U^IV, the behaviour of the polarogram depends upon the acidity of the medium. In 0.1 M H₃PO₄ solution, a single wave is obtained which is characterised by a minimum due to the formation of an insoluble U^III phosphate. In 0.6 M H₃PO₄ and 1 M H₃PO₄ solutions two waves appear. The two waves join together to form a single wave representing the reduction of U^VI to the U^IV, by increasing the acidity of the medium or by the addition of gelatin. The diffusion coefficient of the phosphate complex varies with the concentration of H₃PO₄. It possesses a maximum value of 6.25×10^–6 cn²/sec in 0.5 M H₃PO₄ solution in absence of gelatin and of 5.59×10^–6 cm²/sec in presence of 0.005% gelatin.Part II: See Z. analyt. Chem. 176, 250 (1960).     

Polarographic analysis. I

Summary Reduction of Cu^II in 0.5 M NaOH containing triethanolamine proceeds irreversibly. A similar behaviour is observed in acetate buffer of p_H 6. A reversible wave is obtained in (NH₄)₂CO₃ containing EDTA. The diffusion current measured at the proper voltage is proportional to the Cu^II concentration within a wide range. The waves in 0.5 M NaOH are not well developed being better in acetate buffer and in the presence of EDTA. Ammoniacal solutions containing EDTA can be utilised for the simultaneous estimation of Fe^III and Cu^II. A mixture of Fe^III, Cu^II and U^VI can be fairly well analysed in a medium of (NH₄)₂CO₃ containing EDTA.     

Polarographic Investigations of Functionalized Alkanephosphonic Acids. Part II

Abstract

In this presentation we attempted to verify the enigmatical problem of the polaro-graphical activity of the phosphonic function, especially its electrochemical reduction. Thus, the first report on the polarographic activity of the nitro substituted phenylphos-phonic acid was presented by Kosolapov and Jenkins in 1957 [2].     

Polarographic analysis of the mixed-ligand system Cu(II)-glycine-glycinate

The polarographic method has been applied to the study of the mixed-ligand system Cu(II)-glycine-glycinate, in aqueous medium, at I = 1.0M (NaClO(4)) and 25 -/+ 0.1 degrees . The stabilization of the mixed complex [CuG(G(-))](+) has been made clear and its stability constant (beta(11) = 1 x 10(9)) has been determined. The stability constants of the complexes [CuG]I(2+) (beta(10) = 17), [CuG(2)](2+) (beta(20) = 230), [Cu(G(-))](+) (beta(01) = 2.1 x 10(8)) and [Cu(G(-))(2)] (beta(02) = 1.7 x 10(15)) have also been calculated.     

Polarographic analysis of the reduction waves of Pt(II)-SATSC complex

A polarographic study of the Pt(II)-salicylaldehyde thiosemicarbazone complex in sodium perchlorate as supporting electrolyte is described. In addition to the reduction wave of the complex, a catalytic hydrogen wave is also recorded. The characteristics of this catalytic hydrogen wave are studied under different experimental conditions such as varying acid/complex/supporting electrolyte/surfactant concentrations and also with mercury droptime. Based on these, a probable mechanism for the electrode process has been postulated. Presented at the 12th Annual Symposium in Chemistry held at the Indian Institute of Technology, Madras in March 1987.     

Polarographic analysis of some cephalosporin antibiotics

Summary The cephalosporin derivatives moxalactam, cefazolin, cefuroxime, ceftriaxone and cefotaxime were studied by direct current, sampled direct current, differential pulse polarography and cyclic voltammetry. While moxalactam and cefazolin give rise to one reduction wave, cefuroxime, ceftriaxone and cefotaxime exhibit two reduction waves. The characteristics of corresponding electrode reactions and their analytical parameters are presented and discussed. Optimum pH-ranges for the determination of the five cephalosporins are given. Linear concentration ranges varied from 0.1 to 200 g/ml and limits of determination were of the order of 0.01 to 0.04 g/ml depending on the compound of interest. The precision of the proposed method is excellent with relative standard deviation around 1.3% at a concentration of 0.5 g/ml for all investigated cephalosporins.

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Polarographische Analyse einiger Cephalosporin-Antibiotica

     

Polarographic analysis for corticosteroids: Part 1. The electroanalytical properties of corticosteroids

The electroanalytical behaviour of corticosteroids has been studied in different supporting electrolytes. The reduction patterns are established by examining pH profiles, by constant-potential coulometry, fast-sweep voltammetry, potentiometry with ion-selective electrodes and differential pulse polarography. Dimerization and alcohol formation take place with the reduction of the C-3 keto group resulting in one or two peaks, depending on the number of double bonds in the A-ring and the pH. The C-20 keto group is reduced to an alcohol. Both reduction steps can be used for analytical purposes. The differential pulse peak height is linear with the concentration down to 10^-6 M steroid.     

Polarographic study of the coordinated Cd(II)-leucinate system

The coordinated Cd(II)-leucinate system has been studied polarographically in an aqueous medium and at constant ionic strength (μ = 1.0) (adjusted with NaClO₄). The stabilization of the coordinated species [CdL₂] and [CdL₃]⁻ has been established, with stability constants β₂ = 3.0 × 10⁷ l² mol⁻² and β₃ = 8.2 × 10¹⁰ l³ mol⁻³, respectively.     

Polarographic investigation of the Cu(II) complex with ampicillin

The complex of Cu(II) ion and ampicillin is investigated polarographically in aqueous medium, at pH = 6, an ionic strength = 0.2, and room temperature. The stoichiometric ratio of Cu(II) and ampicillin in the complex, and the stability constant, logK = 5.1, were determined by Lingane's method.     

Polarographic analysis for corticosteroids: Part 3. Determination of Corticosteroids in Single-Component Tablets

The differential pulse polarographic determination of Corticosteroids in single-component tablets is described. The active compounds are extracted from the excipients with a solvent with similar lipophilicity as the polarographic solvents, with a yield of about 100%. The corticosteroid esters and alcohols are determined by standard addition methods. The standard deviations range from 0.5 to 2.5% depending on the excipients and on the method of extraction.     

Simultaneous Polarographic Determination of Lead (II) and TIN (II) by Multivariate Calibration

ABSTRACT

The polarographic waves of lead (II) and tin (II) overlap due to their similar reductive potentials and it is difficult to determine these two components simultaneously without a pre-separation. In this paper, differential pulse polarography (DPP) combined with multivariate calibration approaches, such as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS), were successfully applied to the resolution of overlapping polarographic waves of these two components in the concentration range of 0.05-3.50 mg 1^?1. Satisfactory quantitative results were obtained.     

Polarographic study of the coordinated system Zn(II)-glycine-glycinate ion

A polarographic method has been applied to the study of the mixed-ligand system Zn(II)-glycine-glycinate, in aqueous medium, at I= 1.0 M (NaClO(4)) and 25 +/- 0.05 degrees C. The study of the quasi-reversible waves characteristic of Zn(II) has been carried out by means of a new method of analysis proposed by the authors, which is faster and more accurate than the traditional methods. The stabilization of the coordinated species [ZnG](2+) (beta(10) = 2.0), [ZnG(2)](2+) (beta(20) = 0.71), (Zn(G(-))](+) (beta(01) = 7.6 x 10(4)). [Zn(G(-))(2)] (beta(02)= 4.0 x 10(9)) and [ZnG(G(-))](+) (beta(11) = 1.7 x 10(5)) has been established.     

Differential Pulse Polarographic Investigation of Copper (II) - Cephalexin Complex

Abstract

It has been found by dp polarography that cephalexin forms a complex Cu(CEF)₂, at pH = 8.7, ionic strength μ = 0.2 and room temperature. The stoichiometric ratio and stability constant values have been evaluated by Lingane's and De Ford and Hume's methods. The overall stability constants, logβ₂ = 9.44 and 9.13, have been determined with methods applied.     

Polarographic study of the Co(II)-catalyzed reduction of nitrite

In the potential region corresponding to the reduction of Co(OH)⁺ to the metal, a catalytic polarographic current is observed in an ammoniacal buffer solution containing nitrite ion. In neutral unbuffered media, the catalytic current appears even on the limiting plateau of aquacobalt(II) reduction wave. The catalytic current is due to the reoxidation of an electrodeposited metallic cobalt to Co(II) by nitrite ion. The condition necessary for the catalytic reaction to proceed is the increase in pH at the electrode surface. It is shown that the hydroxide ion is produced as a result of the catalytic reaction.     

Polarographic reduction of cobalt(II) ion in presence of resacetophenoneoxime

Analytical and Bioanalytical Chemistry -