Showing papers on "Polarography published in 2011"

Voltammetric Behavior of Methotrexate Using Mercury Meniscus Modified Silver Solid Amalgam Electrode

Abstract: Voltammetric behavior of methotrexate (MTX), an important chemotherapeutic drug, has been investigated using electrochemical methods: cyclic voltammetry, direct current voltammetry and differential pulse voltammetry on a mercury meniscus modified silver solid amalgam electrode (m-AgSAE). The obtained results have been compared with those obtained using a hanging mercury drop electrode (HMDE). The optimal conditions for its determination have been found in a Britton-Robinson buffer of pH 5 with the limit of detection equal to 1.8 nM. RSD at this concentration level amounted to less than 4 %. The proposed procedure of determination was verified on a real drug containing MTX.

Polarographic method for determination of n-oxide, n-oxide-sulfoxide and sulfoxide metabolites of chlorpromazine

Abstract: Cathode ray polarography has been used to measure chlorpromazine-N-oxide, N-oxide sulphoxide and chlorpromazine sulphoxide in mixtures. The response was linear when the metabolites were present in the range 10−5 to 5 times 10−8m in aqueous solutions. Reductive polarography of the mixed oxides in solution gave an additive wave from which individual oxides were determined by subtraction. Ultraviolet and Potentiometrie titration methods were used to determine the pKa values of the oxide metabolites of chlorpromazine. The mechanism of the reduction process was investigated using d.c. polarography and preparative micro-electrolysis. Polarographic analysis was applied to the determination of the metabolites after their separation from urine, plasma and microsomal preparations.

Electrochemical reduction of flutamide and its determination in dosage forms and biological media

Abstract: Electrochemical reduction of flutamide, non-steroidal anti-androgen was studied at different pH and concentrations at a dropping mercury electrode/hanging mercury drop electrode using different polarographic techniques. Differential pulse polarography was used to establish an electroanalytical procedure for the determination of flutamide in pharmaceutical formulations, urine and serum samples. The cathodic peak observed is attributed to the reduction of nitro group and found to be ph dependent and useful for quantitative estimation. The single step reduction wave/peak observed was found to be irreversible and diffusion controlled. The lower standard deviation of 1.58% with the developed procedure sample analysis can be carried out without pre-treatment or extraction or prior separation of the sample before determination. Key words: Flutamide, differential pulse polarography, pharmaceutical formulations, urine, serum.

The application of differential pulse voltammetry at the glassy carbon electrode to multivitamin analysis.

Abstract: Differential pulse voltammetry at the glassy carbon electrode has been applied to the determination of ascorbic acid, pyridoxine and folic acid in a multivitamin preparation The individual vitamins all gave well-defined peaks in the anodic region with a linear response of peak current to concentration The water-soluble vitamins were extracted into aqueous solution and folic acid into dibasic potassium phosphate solution Before determination of pyridoxine, the ascorbic acid peak was depressed by reaction with formaldehyde Iron (II) present in the multivitamin preparation did not interfere with the analysis The voltammetric method compared favourably in terms of accuracy and precision with official methods: it was found to be much simpler, with sample manipulation kept to a minimum The method was found to be generally applicable to the determination of the vitamins in several multivitamin preparations, or, in simplified form, to the determination of the individual vitamin preparations

Voltametric determination of vancomycin in dosage forms through treatment with nitrous acid.

Abstract: Two methods are described for the determination of vancomycin (vancomycin hydrochloride, CAS 1404-93-9) in its dosage forms. The two methods involve a prior treatment with nitrous acid then measuring the formed nitroso derivative, either spectrophotometrically or polarographically. In the spectrophotometric method, the absorbance-concentration plot is rectilinear over the range of 4-32 μg/ml with minimum detectability of 2.7 μg/ml (1.8 × 10 −6 mol/1). The apparent molar absorptivity is 4.084 × 10−41 • mol−1 cm−1and A (1 %, 1 cm) is 275. The reaction product was also found to be polarographically reducible at the Dropping Mercury Electrode (DME) with E1/2 of -0.9 V vs. Ag/AgCl electrode and a diffusion current constant (Id) of 0.85 ± 0.02. The cathodic current produced was found to be diffusion controlled with some adsorption contribution. The calibration plot was linear over the range of 0.015-0.06 mmol l−1 for direct current (DCt) mode and from 0.005-0.05 mmol l−1 for differential pulse polarography (DPP) mode with minimum detectability of 2.4 × 107 mol l−1 using the latter technique. The results obtained were statistically compared with those given with the official B.P. method and were in good agreement.

Polarography of some purine derivatives

Abstract: CERTAIN purines and purine derivatives are known to be antitumour agents because of their ability to act either as antagonists or antimetabolites in cell metabolic During the syntheses and study of some of these compounds a rapid and sensitive method for the detection of certain functional groups was needed. Because the ultra-violet absorption spectra of the purines lie close together in a region where they are often difficult to distinguish, and because the bands in the infrared have not yet been definitely assigned, we have been investigating the use of the polarograph as an analytical tool. The comprehensive review on the subject of the nucleic acids and their chemistry4, notes only two references to the application of polarography : Heath5 has shown that of the naturally occurring purine and pyrimidine ribonucleotides, only adenylic acid and its derivatives are reduced in 0.1M perchloric acid at the 2.0 dropping mercury electrode. Cavalieri and Lowya have studied a series of variously

Polarography—past, present, and future

Abstract: Polarography was first developed as an automated method of voltage-controlled electrolysis with dropping mercury electrode. The spontaneously renewed pure electrode surface provided reproducible electrochemical results which enabled scientists to work out adequate theory and rich analytical applications. The original method was then instrumentally modified in various ways. Later, hanging mercury drop was added as an alternative indicator electrode—in this way, polarography turned formally into voltammetry with mercury drop electrodes. Beside, in potential-controlled electrolysis, the mercury drop electrodes have been also used in current-controlled electrolysis (chronopotentiometry)—there, it has provided new experimental effects. Polarography has thus gradually covered a wide field of electrolytic methods based on the use of mercury electrodes, in which it continues developing.

Electrochemical reduction of dodecylpyridinium bromide in aprotic solvents: Mechanistic studies

Abstract: Reduction mechanism of 1-dodecylpyridin-1-ium bromide (DPBr) in dimethylsulfoxide has been studied on mercury electrode. Based on the classical polarographic methods as well as on the use of AC techniques it was shown that DPBr is reduced in a reversible one electron transfer step followed by dimerization of the corresponding radical species. Reduction process is accompanied by the adsorption phenomena even in the non-aqueous solvents. Possible modes of DPBr adsorption have been studied by the ex situ scanning tunnelling microscopy (STM) imaging of these molecules on highly oriented pyrolytic graphite.

Electro chemical study and polarographic assay of Clonazepam formulations

Abstract: Electrochemical reduction behaviour of clonazepam has been carried out, by employing d.c. polarography, cyclic voltammetry, a.c. polarography and differential pulse polarography in the supporting electrolytes of the pH ranging from 2.0 to 12.0. The two - step reduction waves are found to be irreversible and diffusion controlled. Differential pulse polarography has been developed for the quantitative estimation of clonazepam in different pharmaceutical preparations without any prior separation using standard addition method. Kinetic parameters such as transfer coefficient, diffusion coefficient and heterogeneous forward rate constant are evaluated and reported. On the basis of the experimental results, a reduction mechanism is suggested for clonazepam.

Electrochemical investigation of 2,2-dinitroethene-1,1-diamine (FOX-7) in aqueous media

Abstract: Redox properties of 2,2-dinitroethene-1,1-diamine (FOX-7) were electrochemically investigated by DC polarography, cyclic voltammetry and preparative electrolyses, and electroreduction products were analysed. The polarographic reduction of FOX-7 in aqueous buffered solutions exhibited a total sum of limiting currents corresponding to the expected 18 electrons. This result fits well with the chemical reduction of this energetic material resulting in ethan-1,2-diamine. Exhaustive electrolysis, however, did not yield this product and the passed charge for total degradation of this compound corresponds only to 4–7 F. As the main products, gaseous N2, N2O, NO and NH3 were proved by combination EC–GC–MS and, besides that, nitrite anions and ammonia ions were identified by other methods. All these observations suggest that instead of electrochemical reduction, an electrochemically initiated degradation process accompanying the exhaustive electrolysis occurs. This seems to be analogous to the chain of reactions during explosion, which are slowed down by a very low concentration and cooled by the solvent.

Applications of polarography in pharmaceutical analysis.

Abstract: INTRODUCTION THE polarographic method of analysis was devised by Professor J. Heyrovskjr in Prague about 25 years ago, but it is only during the last ten years that polarography has been accepted for pharmaceutical analysis. Nevertheless, it is now agreed that the technique is of unquestionable value and the polarograph is assured of a permanent place among the complex equipment of a modern analytical laboratory. In the past there has been a tendency among some enthusiasts to be uncritical of polarographic methods and to use a polarographic procedure whether or not some other more satisfactory method exists. Some of the polarographic analyses suggested in the literature need complicated chemical separations and do not compare favourably with simpler colorimetric and volumetric methods. Whenever a new analytical problem is being examined, a polarographic approach should always be considered, but, before any method is adopted for routine use, its merits must be compared with those of m‘ethods based on other analytical techniques. For many pharmaceutical problems the polarograph can offer a method that has advantages over all other techniques. The fundamental principles of polarographic analysis were worked out in Heyrovskfs laboratory and are adequately described in Kolthoff and Lingane’sl and Heyrovskfs2 monographs. These survey polarographic literature up to the beginning of 1941. Stock‘ss and Muller’s4 reviews provide useful introductions to practical polarography and von Stackelberg’s5 book covers the literature until the end of 1949.

Components of the Net Current in Differential Pulse Polarography. Part 2. Kinetics and Adsorption

Abstract: Components of the net response in differential pulse polarography were studied theoretically, assuming gradually changing electrode rate constant or strength of the reactant adsorption. The difference between the maximum potential of the peak component and the half-wave potential of the wave component appear as an important parameter. From its value, the electrode rate constant can be calculated even when the standard potential is not known. In a reversible process, effects of the reactant adsorption on the mentioned separation are less pronounced. The results were compared with experimentally obtained effects. For deeper insight into the applicability of this approach, additional experimentally obtained polarograms (that reflect different potential/timing parameters or changing character of the electrode process) should be studied in terms of their components.

The polarographic determination of chlorpromazine and chlorpromazine sulphoxide.

Abstract: Cathodic polarography of solutions containing between 0·1 and 5·0 μg/ml of both chlorpromazine and its sulphoxide enables the sulphoxide to be determined directly. Reductive polarography of the solution after bromination gives an additive wave from which the chlorpromazine is determined by subtraction. The method has been applied to urine, interfering substances being removed by ion-exchange on Amberlite resins.

Polarographic Investigations of Certain Propiophenone Benzoic Acid Hydrazones

Abstract: The electrochemical behavior of (a) propiophenone benzoic acid hydrazone, (b) 4’– methyl propiophenone benzoic acid hydrazone, (c) 4’– methoxy propiophenone benzoic acid hydrazone, (d) 4’– hydroxy propiophenone benzoic acid hydrazone and (e) 4’– chloro propiophenone benzoic acid hydrazone were investigated at the dropping mercury electrode by employing DC polarography. The variables that influence the electrode process were extensively studied. All compounds under investigation gave a single well defined polarographic wave. The mechanism for the electrode process was proposed in acid as well as in basic media.

Electrochemical study of gallium(III) with l-glutamine at the dropping mercury electrode

Abstract: Gallium complexes of l-glutamine have been studied polarographically in aqueous media. The reduction was found to be irreversible and diffusion controlled in the presence of 0.1 M KNO3 and 0.002% Triton-x-100. The values of kinetic parameters, transfer coefficient (α n), and formal rate constant ( $$ k_{{{\text{f}},{\text{h}}}}^{0} $$ ) of the electrode reactions were calculated by Koutecky's method. The stability constants and composition of the gallium(III)-l-glutamine complexes were evaluated with the help of the Deford-Hume method. The values of stability constants of 1:1, 1:2, and 1:3 gallium(III)-l-glutamine complexes are 1.35, 6.5, and 1,350 at 30 °C, respectively. The values of thermodynamic parameters, the free energy of activation, the enthalpy of activation, and the entropy of activation have been determined at 30 °C. The formation of the metal complexes has been found to be non-spontaneous, endothermic in nature, and entropically favorable at higher temperature.

Polarographic Behavior of Manganese(II) in the Presence of Oxalate Ions in Perchlorate and Sulfate Solutions

Abstract: The dc polarographic method has been applied to study coordination equilibria between Mn(II) and oxalate ions in perchlorate and sulfate solutions. The stoichiometries of complexes formed in solution and those reduced at a dropping mercury electrode were established. The stability constants of the Mn(II) oxalate and sulfate complexes, as well as their diffusion coefficients, were determined at a constant ionic strength 0.5 mol⋅L−1 and 25 °C. The stabilities of these Mn(II) complexes were compared with the corresponding complexes of other divalent metal ions. The polarographic method was able to identify complexes that have not been established by other methods and to determine their stability constants with high accuracy.

Determination of copper(II) in water, vegetables and alloy samples with polarography at DME using piperidine dithiocarbamate by catalytic hydrogen currents

Abstract: Facile, rapid and sensitive catalytic hydrogen polarographic method for the determination of Cu(II) with Piperidine dithiocarbamate (pip-DTC) in various water, vegetables and alloys was described in the present paper. The method was based on the catalytic hydrogen wave of pip-DTC-Cu(II) complex in the presence of NH4Cl-NH4OH medium at pH 6.6 and produce a catalytic hydrogen wave at –0.35 V vs SCE. Optimum parameters such as effect of pH, NH4Cl-NH4OH,AmmPip- DTC, metal ion concentration and excipient effect on peak height were investigated to enhance the sensitivity of the present method. The proposed method was applied for the determination of Cu(II) in various water, vegetables and alloys and the results obtained were compared with the differential pulse polarography in terms of detection limits.

Ni(II)-ammonium morpholine dithiocarbamate complex studies with polarography at DME by catalytic hydrogen currents in various environmental samples

Abstract: This paper dealswith the simple, sensitive catalytic hydrogen polarographic method for the determination ofNi(II) withAmmMorpholine dithiocarbamate (AmmMor-DTC) in various water samples and agricultural materials. The method was based on the catalytic hydrogen wave ofAmmMor-DTCNi( II) complex in the presence of NH4Cl-NH4OH medium at pH 6.0 and produce a catalytic hydrogen wave at -1.30 V vs SCE. Various parameters such as effect of pH, NH4Cl-NH4OH,AmmMor-DTC,metal ion concentration and foreign ion effect on peak height were investigated to enhance the sensitivity of the present method. The obtained results were in good agreement with differential pulse polarographic method in terms of terms of StudentÂÂ’s ‘tÂÂ’-test and Variance ratio ‘fÂÂ’-test. The proposed method was applied for the determination ofNi(II) in various water samples and agriculturalmaterials.

Polarographic and voltammetric determination of genotoxic nitro derivatives of quinoline using mercury electrodes

Abstract: Electrochemical behavior of genotoxic nitro derivatives of quinoline, namely 5-nitroquinoline (5-NQ), 6-nitroquinoline (6-NQ) and 8-nitroquinoline (8-NQ), was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a classical dropping mercury electrode (DME), and by differential pulse voltammetry (DPV) and adsorptive stripping differential pulse voltammetry (AdSDPV), both at a miniaturized hanging mercury drop minielectrode (HMDmE), in buffered aqueous (for 5-NQ) or aqueous-methanolic (for 6-NQ and 8-NQ) solutions. Optimum conditions were found for the determination of 5-NQ, 6-NQ and 8-NQ by DCTP at DME (with limits of quantification, L Q ≈ 9 × 10 –7 , 3 × 10 –7 and 2 × 10 –6 mol l –1 , respectively), by DPP at DME ( L Q ≈ 1 × 10 –8 , 9 × 10 –8 and 1 × 10 –7 mol l –1 , respectively), by DPV at HMDmE ( L Q ≈ 2 × 10 –8 , 1 × 10 –7 and 1 × 10 –7 mol l –1 , respectively), and by AdSDPV at HMDmE ( L Q ≈ 1 × 10 –8 mol l –1 for 8-NQ; an attempt at increasing the sensitivity using AdSDPV at HMDmE was not successful for 5-NQ and 6-NQ). Practical applicability of the developed methods was verified on the direct determination of the studied compounds in model samples of drinking and river water in submicromolar concentrations and on the determination in model samples of drinking and river water using preliminary separation and preconcentration by solid phase extraction (SPE) in nanomolar concentrations.

Polarographic and voltammetric determination of genotoxic 2-aminofluoren-9-one at mercury electrodes

Abstract: Electrochemical behavior of genotoxic 2-aminofluoren-9-one (2-AFN) was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a classical dropping mercury electrode (DME), and by DC voltammetry (DCV), differential pulse voltammetry (DPV), and adsorptive stripping differential pulse voltammetry (AdSDPV), all at a miniaturized hanging mercury drop minielectrode (HMDmE), in buffered aqueous-methanolic solutions. Optimum conditions were found for the determination of 2-AFN by DCTP at DME in the concentration range from 1 × 10 –6 to 1 × 10 –4 mol l –1 (with a limit of quantification ( L Q) of 5 × 10 –7 mol l –1 ), by DPP at DME (from 1 × 10 –7 to 1 × 10 –4 mol l –1 ; L Q ≈ 1 × 10 –7 mol l –1 ), by DCV and DPV at HMDmE (both from 1 × 10 –7 to 1 × 10 –4 mol l –1 ; L Qs ≈ 2 × 10 –7 and 1 × 10 –7 mol l –1 for DCV and DPV, respectively), and by AdSDPV at HMDmE (from 2 × 10 –9 to 1 × 10 –7 mol l –1 ; L Q ≈ 4 × 10 –9 mol l –1 ). Practical applicability of the developed methods was verified on the direct determination of 2-AFN in model samples of drinking and river water in nanomolar to micromolar concentrations.

A polarographic limit test for sulphoxide in chlorpromazine

Abstract: Twin cell subtractive cathode ray polarography can be used as a quantitative limit test for from 0.5% to 2.0% of chlorpromazine sulphoxide in chlorpromazine. 0.05% of the impurity is detectable by derivative polarography.