Polarographic behaviour of 2-benzilidenimino-benzohydroxamic acid (2-BIBH) and 2-BIBH-Mo(VI) system

The polarographic behaviour of 2-benzilideniminobenzohydroxamic acid (2-BIBH) solutions and of 2-BIBH solutions in the presence of Mo(VI) have been studied by using differential pulse polarography and cyclic voltammetry. The polarographic characteristics of the resulting waves have been studied and possible mechanisms of the processes involved have been proposed. A linear relationship has been observed betweenI _p and Mo(VI) concentration in the range 2×10^–6 to 1.6×10^–5 M when using 3×10^–4 M 2-BIBH. Standard deviations of 5.6×10^–8 and 1.2×10^–8 M were found for 3×10^–6 and 8 × 10^–6 M Mo(VI), respectively.     

Some electroanalytical aspects of using pulse polarography for determination of Ge(IV)

Summary Presented data give some informations of analytical importance as a result of pulse polarographic investigations of Ge(IV) in KCl solutions within pH range 3–12 at Ge concentration from 1×10^–4 to 2.5×10^–6 M. It was shown that Ge(IV) can be polarographically active in acidic solution but its reduction interferes with hydrogen gas development. The addition ofp-quinone enables the determination of Ge(IV) without this interfering effect.Suggested explanation of the observed changes in polarographic curves dependent on pH and Ge concentration based on the existence of several polarographically active forms.

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Elektroanalytische Bemerkungen zur pulspolarographischen Bestimmung von Ge(IV)

Zusammenfassung Unsere Ergebnisse bieten einige Informationen über die pulspolarographische Bestimmung von Ge(IV) in KCl-Lösungen innerhalb pH 3–12 und bei Ge-Konzentrationen zwischen 10^–4 und 2,5×10^–6 M. Es wurde gezeigt, daß Ge(IV) in saurer Lösung polarographisch aktiv ist, seine Reduktion aber durch Wasserstoff-Entwicklung gestört wird. Der Zusatz vonp-Chinon beseitigt diese Störung. Die Änderung der polarographischen Kurven je nach Ge-Konzentration und pH beruht vermutlich auf der Existenz verschiedener polarographisch aktiver Formen.

     

Polarographic behaviour and determination of beclomethasone dipropionate

The polarographic behaviour of beclomethasone dipropionate in Britton-Robinson buffers containing 40% methanol as a solubilizer has been studied. Over the pH range 1.8–12, a cathodic wave was produced, which was characterised as being irreversible, diffusion controlled and free from adsorption phenomena. The number of electrons involved in the reduction was found through comparative study with spironolactone. Using direct current polarographic mode, the limiting current concentration plot is rectilinear over the range 2.5 × 10^–5 to 4 × 10^–4 mol/1 with a detection limit of 2.5 × 10^–6 mol/1. A method has been developed for the determination of the drug in aerosols and creams, the results being in agreement with those obtained by the official method.     

Determination of acipimox in capsules by differential pulse polarography

A differential pulse polarographic (DPP) method has been developed for the determination of acipimox in its pharmaceutical formulations. Using Sörensen buffer pH 6.0 as supporting electrolyte a single, irreversible peak occurred at –0.79 V vs an Ag/AgCl reference electrode. The peak height vs concentration plot was found to be linear over the range of 10^–6 to 6 × 10^–4 mol/l. The detection limit is 60ng/ml. The analysis of a series of 10 Olbetam® 250 mg capsules showed an overall standard deviation of ± 4.18 mg and a S_rel of ± 1.66%, respectively.     

Polarographic and voltammetric behaviour of 2-hydroxy-3-tert-butyl-5-methylazobenzene

The polarographic and voltammetric behaviour of 2-hydroxy-3-tert-butyl-5-methylazobenzene has been studied in aqueous-ethanol mixtures of different pH using DCP and DPP polarographic and CV and SWV voltammetric methods. The reduction of the azo linkage takes place via two electrons at pH > 7, but four electrons at pH < 7 in aqueous-ethanol mixtures. It has been determined that there is a linear relationship between the current and concentration and the lowest detection limit has been found as 1 × 10^–7 M (for SWV).     

Polarographic studies on some arylarsonic acids

Summary The polarographic behaviour of a series of substituted phenylarsonic acids over the concentration range 5×10^–5M–10^–3M and pH range 0–3 was studied and a mechanism for the polarographic reduction proposed, taking into account the results of various analyses performed on the products of macro-scale electrolytic reductions. A method for the analysis of phenylarsonic acids utilising the reduction wave is also presented.

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Polarographische Untersuchungen einiger Arylarsonsäuren

Zusammenfassung Das polarographische Verhalten einer Reihe von substituierten Phenylarsonsäuren wurde im Konzentrationsbereich 5 · 10^–5M–10^–3M bei pH 0–3 untersucht und ein Mechanismus für die polarographische Reduktion aufgestellt, der auch die Ergebnisse von elektrolytischen Reduktionen im Makrobereich berücksichtigt. Eine Methode für die Analyse von Phenylarsonsäuren, mit Hilfe der polarographischen Reduktionsstufe wird beschrieben.

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Research Institute for Technical Physics of the Hungarian Academy of Sciences, Budapest IV.     

Investigations on the redox character of dithizone by voltammetric methods : Part I.The reduction of dithizone in aqueous solutions

The mechanism of the electrochemical reduction of dithizone to the corresponding hydrazo compound, diphenylthiocarbazide, has been examined in detail by polarographic and voltammetric techniques over a wide pH range. The reaction is reversible and dithizone can be determined polarographically in the range 10^-3–10^-5M. This polarographic behaviour suggests new applications of dithizone as an electroanalytical reagent.     

Polarographic study of a benzodiazepinooxazole: Oxazolam

Summary The polarographic behaviour of 10-chloro-2,3, 7,11b-tetrahydro-2-methyl-11b-phenyloxazolo-[3,2-d][1,4]-benzodiazepin-6(5H)-one (Oxazolam) was studied in the pH range 1–12. The reduction processes of Oxazolam and its hydrolysis product are irreversible and their currents are predominantly diffusion-controlled. The linear relationship between current and Oxazolam concentration in sulphuric acid medium permits its polarographic determination up to 6.08×10^–5 mol/l. The detection limit was 1.52×10^–7 mol/l (50 ppb). The reproducibility of the method in terms of relative standard deviation was 1.74% and 1.85% for ten determinations at 1.48×10^–5 mol/l and 1.37×10^–6 mol/l levels, respectively. The method developed was applied to the determination of the compound in its formulations, Hializan-10 mg, obtaining errors lower than 2%.

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Polarographische Untersuchung eines Benzodiazepinoxazols: Oxazolam

     

Rapid determination of telmisartan in pharmaceuticals and serum by the parallel catalytic hydrogen wave method

The polarographic characteristics of telmisartan have been investigated in 0.8 mol L^–1 NH₃.H₂O–NH₄Cl (pH 8.9)–0.01 mol L^–1 H₂O₂ as supporting electrolyte. The results demonstrate that the polarographic reduction wave at ca. –1.30 V in the absence of H₂O₂ is a catalytic hydrogen wave, and the reduction wave enhanced by H₂O₂ is a so-called parallel catalytic hydrogen wave. The analytical sensitivity of the parallel catalytic hydrogen wave is ca. 60 times higher than that of the corresponding catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave a novel method has been developed for determination of telmisartan by linear sweep polarography. The calibration curve is linear in the range 2.0×10^–8–2.0×10^–6 mol L^–1 and the detection limit is 1.0×10^–8 mol L^–1. The precision is excellent with relative standard deviations of 2.6% at a concentration of 1.0×10^–7 mol L^–1 telmisartan. The proposed method has been applied to the direct determination of the telmisartan in capsule forms and biological samples. The proposed method has been proved to be advantageous over existing CZE and MEKC methods in simplicity, rapidity, and reproducibility.     

Determination of oxytetracycline in urine and human serum by differential pulse polarography

Summary A differential pulse polarographic method for the determination of oxytetracycline in urine and human serum in acid media (HClO₄ of pH 2) is proposed. The effects of the amount of sample taken and the concentration of HClO₄ present were investigated. The detection limit was 5.5×10^–6 mol/l. The standard deviation of the determination of 5.5×10^–5 mol/l of oxytetracycline in 2 ml of urine was 1.7×10^–6 mol/l and that of the determination of 5.5×10^–5 mol/l of oxytetracycline in 2 ml of human serum was 1.9×10^–6 mol/l.

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Bestimmung von Oxytetracyclin in Urin und Humanserum durch Differential-Pulspolarography

     

Polarographic and voltammetric determination of trace amounts of 2-nitronaphthalene

The polarographic behaviour of 2-nitronaphthalene was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a dropping mercury electrode, and differential pulse voltammetry and adsorptive stripping voltammetry, both at a hanging mercury drop electrode. Optimum conditions have been found for the determination of 2-nitronaphthalene by the given methods in the concentration ranges of 2×10^–6–1×10^–4, 2×10^–7–1×10^–4, 1×10^–8–1×10^–4 and 2×10^–9–1×10^–8 M, respectively. Practical applicability of these techniques was demonstrated by the determination of 2-nitronaphthalene in drinking and river water after its preliminary separation and preconcentration using liquid–liquid and solid-phase extraction with limits of determination of 3×10^–10 M (drinking water) and 3×10^–9 M (river water).     

Polarographic behaviour and determination of azintamide

Azintamide was found to be reduced at the dropping mercury electrode over the pH range 1.8–9.4 in Britton Robinson buffers containing 20% methanol. At pH 7.42 a well defined diffusion-controlled cathodic wave was produced. The limiting current versus concentration plot was linear over the range 0.025–1.0 mM and 0.005–1.0 mM in the DC_t and DPP modes, respectively, with a lower detection limit of 1 × 10^–7 M by the latter technique. A mechanism for the electrode reaction has been proposed. The method has been applied to the determination of azintamide in tablets, and the results obtained were in agreement with those obtained by a reference method.AvH Scholar 1989–1991.     

Electrochemistry of electropolymerized tetra (p-aminophenyl)porphyrin nickel film electrode and catalytic oxidation of acetaminophen

A polymer film of tetra(p-aminophenyl) porphyrin nickel was obtained at a glassy carbon electrode by a cyclic voltammetric method. Cyclic voltammograms of the film electrode exhibited two stable redox waves with anodic peak potential at 0.43V and cathodic peak potential at 0.30 V in 0.5M NaOH aqueous solution. The electrocatalytic characteristics of the film electrode were studied by cyclic voltammetry, a. c. impedance analysis and other methods. The oxidation peak current increased linearly with the addition of acetaminophen to the aqueous NaOH medium in the range 1 × 10^–6–2 × 10^–4 M acetaminophen. The performance of the electrode was verified by the determination of acetaminophen in a paracetamol preparation.     

Polarographic study of a triazolobenzodiazepine: Estazolam

Summary The polarographic behaviour of 8-chloro-6-phenyl-4H-s-triazolo(4,3-a)-(1,4)-benzodiazepine (estazolam) was studied in the pH range 3–10. The reduction process is irreversible and the current is diffusion-controlled. The linear relationship between current and estazolam concentration permits its polarographic determination in the range 3.4·10^–7–1.0·10^–4 M. The detection limit was 1.7·10^–7 M. The reproducibility of the method in terms of its relative standard deviation was 1.00% and 1.14% using ten determinations at the 2.4·10^–5 M and 3.4·10^–6 M levels respectively.

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Polarographische Untersuchung des Triazolbenzodiazepins Estazolam

     

Ion-Selective Electrodes Based on Adamantylcalix[4,8]arenes for the Determination of Alkali Cations

Calix[4,8]arenes bearing adamantyl substituents in the upper rim and ethoxycarbonylmethoxy groups in the lower rim of the macrocycle were proposed as ionophores in membranes of ion-selective electrodes (ISEs) for determining alkali cations. Depending on the number of phenolic fragments (n) in the calixarene molecule, ISEs respond to either sodium (n = 4) or cesium (n = 8) ions. Sensors based on membranes that, along with ionophores, contain tetraphenyl borate ions as a lipophilic additive are selective for Na and Cs ions in the presence of other alkali metals. They exhibit almost theoretical responses over the concentration range from 1 × 10^–4 to 1 × 10^–1 M at pH 5.5–12 for Na-SE and pH 3–11 for Cs-SE, respectively.     

Polarographic behaviour of n-butyl thioglycolate

The polarographic behaviour of n-butyl thioglycolate, [HSCH₂OOC(C₄H₉)] has been studied in 25% ethanol, 0.1M-KNO₃ and 0.002% Triton X-100 in the pH range 1.96–11.84 at the d.m.e. The polarograms consist of two waves, a pre-wave of constant height followed by a normal anodic wave. The electrode reaction is reversible and diffusion controlled involving one electron transfer process. The maximum number of moles adsorbed per unit area is 1.30×10^–9 mole/cm², i.e. 7.82×10¹⁴ molecules/cm², which corresponds to an area 12.84 Å per adsorbed molecule. The adsorption coefficient and molar adsorption energy have been calculated to be 43.4×10⁴ and 142.8 kcal/mole respectively. The dissociation constant (pK) of the sulphydryl group is found to be 9.4.With 1 Figure     

Radiochemical Neutron Activation Analysis of Rhenium and Ammonium Perrhenate Samples

A procedure for the radiochemical neutron activation analysis of rhenium and ammonium perrhenate samples was developed. The procedure provides the determination of about 30 impurity elements present in concentrations of n× 10^–4to n× 10^–8mass % with RSD of 20–30%. An AV-17 anion exchanger–nitric acid solution system was used, which allows the selective separation of rhenium from a wide variety of elements.     

Indirect determination of bilirubin by linear sweep polarography

Summary A polarographic method for the determination of bilirubin is described: In hydroquinone-sodium phosphate buffer (pH 11.2) medium, bilirubin can be rapidly oxidized to a green product, which causes a sensitive polarographic wave at –0.83 V (vs. SCE); the peak current of the wave is linear with the bilirubin concentration over a range of 3×10^–7 to 5×10^–6 mol/l. It has also been found to be more stable than that produced by bilirubin; in general, it can remain unchanged for about 1 h at room temperature and exposure to air. This overcomes the instability of bilirubin for its direct assay to a certain extent. If a small amount of EDTA is added to the solution, the stability of the wave can be further improved. In addition, the characteristics of the wave have been investigated and it has been confirmed to be an adsorptive catalytic wave. The chemical reaction mechanism is discussed and the green product is confirmed to be biliverdin.     

Determination of methylviologen (Paraquat) by differential pulse polarography

Summary Determination of Methylviologen (Paraquat) by Differential Pulse Polarography The second reduction wave of methylviologen (Paraquat) has been studied at pH 2 by different polarographic techniques. The limiting current is diffusion-controlled. Evidence for dimerization of the radical formed in the first reduction step has been obtained. The n values for the reduction process have been calculated at concentration levels where the dimer and the monomer predominate. Paraquat can be determined by differential pulse polarography in the 6.0×10^–5–4.0×10^–7 M concentration range, the limit of determination being 1.7×10^–7 M. The method has been applied to paraquat determination in commercial herbicides.     

Determination of propazine by differential pulse polarography in micellar and emulsified media

An electroanalytical study of the herbicide propazine's reduction process in micellar solutions and oil-in-water emulsions is reported. The anionic surfactant sodium pentanesulphonate was chosen as the most suitable. The differential pulse polarograms of micellar solutions had two reduction peaks below pH 2.0, whereas only one peak was obtained above pH 2.O. Ethyl acetate was chosen as the organic solvent to form propazine emulsions. Unlike in micellar solutions, the DPP polarograms of propazine emulsions showed only one peak even at pH < 2.0, suggesting that propazine hydrolysis was hindered in the emulsified medium. The limiting current is diffusion-controlled and the electrode process is irreversible. Propazine can be determined by differential pulse polarography over the 1.0 × 10^–1 – 1.0 × 10^–1moll^–1 and 1.0 × 10^–15 – 4.0 × 10^–1 moll^–1 concentration ranges and the limit of detection was 2.8 × 10^–1 moll^–1. Of the potential interferents simazine, methoprotryne and terbutryn (alls-triazines), thiram (a dithiocarbamate), dinoseb (nitrophenolic), and heptachlor (chlorinated cyclo-diene herbicide), only the first two were significant (10% error for equimolar concentrations). The method was applied to the determination of propazine in spiked drinking water. At a concentration level of 2.0 × 10^–1 moll^–1 a recovery of 94 ± 6% was obtained, after tenfold concentration on Sep-Pak.