Determination of nisoldipine in film tablets by differential pulse polarography

Summary A differential pulse polarographic (DPP) method was developed for the determination of nisoldipine in Baymycard^® film tablets without interference from excipients. Nisoldipine is reduced at the dropping mercury electrode in a single, irreversible peak. Linearity between the nisoldipine concentration and the peak height was observed in the 5·10^–4–10^–7 M concentration range. The detection limit is 22 ng/ml. The analysis of a series of 10 Baymycard^® 5 mg film tablets showed a standard deviation of ±0.115 mg and aS _rel of ±2.30%, respectively.

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Gehaltsbestimmung von Nisoldipin in Filmtabletten mittels differentieller Pulspolarographie

Zusammenfassung Eine Bestimmung von Nisoldipin in Baymycard^® Filmtabletten mittels differentieller Pulspolarographie (DPP) wurde entwickelt, die keine Störungen durch Tablettenhilfsstoffe aufweist. Nisoldipin wird an der tropfenden Quecksilberelektrode in einem einzigen, irreversiblen Peak reduziert. Linearität zwischen Nisoldipinkonzentration und Peakhöhe wurde im Konzentrationsbereich von 5·10^–4–10^–7 M festgestellt. Die Bestimmungsgrenze beträgt 22 ng/ml. Die Analyse einer Serie von 10 Baymycard^® 5 mg Filmtabletten ergab eine Standardabweichung von ±0.115 mg, dies entspricht einerS _rel von ±2.30%.

     

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.     

Determination of ethylenediaminetetraacetate and nitrilotriacetate in phytoplankton media by differential pulse polarography

A technique for the analysis of synthetic sea water and phytoplankton media for ethylenediaminetetraacetate (EDTA) and nitrilotriacetate (NTA) by differential pulse polarography has been developed. The addition of approximately 2.4 · 10^-4 M cadmium to the analyte converts a large fraction of either ligand to the reducible cadmium complex. With 5 · 10^-6 M ligand present, the standard deviation is approximately. 6 · lO^-7 M for NTA and 4 · 10^-7 M for EDTA. The presence of competing metal cations, including copper, is not detrimental if the method of standard additions is used.     

Simultaneous determination of selenium and lead in whole blood samples by differential pulse polarography

The polarographic reduction of lead in the presence of selenite gives rise to an additional peak corresponding to the reduction of lead (Pb) on adsorbed selenium (Se) on mercury at −0.33 V. The selenium and lead content can be determined using this peak by the addition of a known amount of one of these ions first and then the second ion. The linear domain range of lead is 5.0×10⁻⁷–2.0×10⁻⁵ M and for selenium 5.0×10⁻⁷–1.0×10⁻⁵ M. Using this method 4.90×10⁻⁷ M Se(IV) and 1.47×10⁻⁶ M Pb(II) in a synthetic sample could be determined with a relative error of +2.0% and 1.8%, respectively (n=4). A recovery test after acid digestion for a synthetic sample was 97% for selenium and 96.5% for lead. The method was applied to 1 ml of digested blood, and 328±23 μg l⁻¹ Se(IV) and 850±62 μg l⁻¹ Pb(II) could be determined with a 90% (n=5) confidence interval.     

Trace analysis of toxic metals,III. Determination of chromium as trivalent chromium by differential pulse polarography

Methods for trace analysis of chromium as Cr³⁺ were investigated, using differential pulse polarography in various media. Determination at the ng/ml-g/ml range can be carried out in KCl/HCl, KCNS/HOAc, and other media. Total concentration of chromium in a solution containing Cr³⁺ and HCrO ₄ ^– can be determined in KCNS/HOAc, and it is found that HCrO ₄ ^– can be converted quantitatively to Cr³⁺. The relative quantity of HCrO ₄ ^– and Cr³⁺ can be determined by the difference between the total chromium concentration and the concentration of HCrO ₄ ^– . The sensitivity (12.5 ng/ml) and accuracy of this method is better than the method that determines total chromium as HCrO ₄ ^– .     

Employment of differential pulse polarography and adsorptive voltammetry for the determination of some sulfonamides

Reduction of sulfonamides in mineral acids was investigated using fast scan differential-pulse polarography (FSDPP). The optimal medium for sulfadimidin, sulfamethoxydin and sulfamethoxypyridazin is 0.01–0.02M HCl, while for phthalazol it is 1M HCl and the latter compound can be selectively determined in the presence of other sulfonamides. Adsorptive properties on the Hg-electrode were analytically used in the case of sulfamethoxypyridazin and phthalazol. Relative standard deviation of all determinations did not exceed 8%.     

Aqueous sulfur species determination using differential pulse polarography

Sulfur species play pivotal roles in biogeochemistry; however, quantification remains difficult because such species are transitory. Our objective was to determine the utility of using differential pulse polarography (DPP) to characterize soluble sulfur species of potential interest in agriculture and environmental quality. Polarographic responses for sulfide, disulfide, pentasulfide, sulfite, thiosulfate, tetrathionate, pentathionate, cysteine, and glutathione were determined. Sulfur in the compounds was categorized as cysteine-S, thiosulfate-S, nonpurgeable or purgeable sulfide-S, or sulfite based on characteristic polarographic responses for each respective category. Nonpurgeable sulfide-S, cysteine-S, and thiosulfate-S were polarographically separated using a pH 8.0 phosphate buffer. Nitrate/bicarbonate (pH 10.0) and acetate (pH 5.0) buffers were used to determine purgeable sulfide-S and sulfite, respectively. Sulfur in water extracts from cysteine-amended soils was quantified using the developed DPP method. Cysteine-, thiosulfate-, and sulfide-S were measured from these extracts without interferences during a 16-d incubation period. The developed DPP method provides qualitative and quantitative information concerning sulfur species in aqueous solutions and is potentially applicable to soil and sediment extracts.     

Determination of bacitracin by differential pulse polarography.

Differential pulse polarograms of pharmaceutical-grade bacitracin exhibit a well-defined double wave at the dropping mercury electrode over the entire pH range 1–8. The current is diffusion-controlled and proportional to the concentration as well as to the biological activity of the sample. The concentration of bacitracin and of zinc—bacitracin can be determined by pulse polarography with a standard deviation less than 2%. The biologically inactive oxidation product (bacitracin F) is reduced at less negative potentials and can easily be determined in the presence of the biologically active components of bacitracin.     

Determination of coumarins by voltammetric techniques in micellar and emulsified media

An electroanalytical study of the oxidation processes of umbelliferone and hymecromone at a glassy carbon electrode in micellar solution and emulsified medium by different voltammetric techniques is described. The non-ionic surfactant Triton X-405 in acetate-buffered medium at pH 4.8 was found to be the most suitable. Different ranges of linearity were obtained in the micellar solutions, depending on the technique used; the limits of determination for differential pulse voltammetry (DPV) at a stationary electrode were 2.9×10^?6 mol l^?1 and 3.3×10^?6 mol l^?1 for umbelliferone and hymecromone, respectively. In the emulsified medium formed with a mixture of toluene and ethyl acetate (3:2), the oxidation processes yielded similar results. With DPV, linear calibration plots were obtained in the ranges 1.0×10^?5–9.0×10^?7 mol l^?1 umbelliferone and 1.0×10^?5–2.0×10^?6 mol l^?1 hymecromone. The media used are predominantly aqueous so that special reference electrodes and solvent purification are not needed.     

Determination of platinum in urine by differential pulse polarography

A method has been developed for determination of platinum in urine, after administration of cis-dichlorodiammineplatinum(II). The diethyldithiocarbamate complex of the platinum(II) is formed and extracted into chloroform, then mineralized with aqua regia. After removal of nitric acid the platinum is complexed with ethylenediamine. This chelate yields a catalytic current at a dropping mercury electrode, which is measurable by differential pulse polarography. The detection limit is ~10 ng ml . The calibration graph is linear over the range 20-800 ng ml .     

Determination of crotonaldehyde in ethanol by differential pulse polarography

The extraction constant of gold bisdiethyldithiocarbamate chloride has been determined (log K' = 81.5± 0.7) by studying the competition from palladium in the extraction of gold with an excess of copper diethyldithiocarbamate in chloroform. Gold bisdiethyldithiocarbamate chloride is an ion pair which can dissociate: a dissociation constant of this compound has been determined by studying the influence of chloride concentration on the extraction of gold with the same reagent. In sulphuric acid medium, the low extraction ratio of gold observed cannot be attributed to extraction of gold bisdiethyldithiocarbamate sulphate as dependence on sulphate concentration has not been obtained. A program for the computation of this type of stability constant from extraction data for mixtures of cations and ligands is given.     

Determination of arsenite and arsenate by differential pulse polarography

Summary Arsenate was determined by differential pulse polarography in acidic solutions in the presence of polyhydroxy compounds. The best medium was found to be 2.0 M aqueous HClO₄ containing 4.5 g d-mannitol in 50 ml solution. The peak heights measured at –0.55 V gave linear calibration curves in the concentration range 20 g/l to 160 mg/l As. Arsenite was similarly determined with mannitol at –0.34 V or without mannitol at –0.42 V. When arsenite and arsenate were present in solution, the simultaneous determination of these compounds in the presence of mannitol was generally not possible because the peak heights at –0.34 V and –0.55 V were influenced by arsenite as well as arsenate. In these cases arsenite was determined at –0.42V in the absence of mannitol. After oxidation of arsenite to arsenate by chlorine water and addition of mannitol, total inorganic arsenic was determined as arsenate at –0.55 V. The arsenate concentration in the sample was found as the difference between the concentrations of total inorganic arsenic and arsenite. The detection limit for arsenite and arsenate was found to be approximately 10 g/l As. This method was successfully used to determine arsenite and arsenate in a synthetic river water sample and some arsenic-containing drinking water samples.

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Bestimmung von Arsenit und Arsenat durch Differential-Pulspolarographie

Zusammenfassung Arsenat wurde durch Differential-Pulspolarographie in saurer Lösung in Gegenwart von Polyhydroxyverbindungen bestimmt. Das günstigste Medium war 2,0 M wäßrige HClO₄ mit 4,5 g d-Mannit in 50 ml. Die bei –0,55V gemessenen Peakhöhen ergaben eine lineare Eichkurve für den Bereich von 20 g/l bis 160 mg/l As. Arsenit wurde auf ähnliche Weise mit Mannit bei –0,34 V oder ohne Mannit bei –0,42 V bestimmt. Bei Anwesenheit von Arsenit + Arsenat in Lösung war eine Simultanbestimmung in Gegenwart von Mannit im allgemeinen nicht möglich, weil die Peakhöhen bei –0,34 V und –0,55 V sowohl von Arsenit als auch von Arsenat beeinflußt werden. In diesen Fällen wurde Arsenit ohne Mannit bei –0,42 V bestimmt. Nach Oxidation zu Arsenat mit Chlorwasser und Zugabe von Mannit wurde dann das Gesamtarsen als Arsenat bei –0,55 V bestimmt; der Arsenatgehalt in der Probe ergab sich aus der Differenz. Die Nachweisgrenze für Arsenit und Arsenat lag bei etwa 10 g/l As. Das Verfahren wurde mit gutem Erfolg für eine synthetische Flußwasserprobe sowie einige Trinkwasserproben angewendet.

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On leave from Jadavpur University, Calcutta, India     

Electrochemical studies of berberine and jatrorubine by pulse polarography

The application of pulse polarography (PP) and differential pulse polarography (DPP) for the quantitative determination of berberine and Jatrorubine in aqueous, acidic solutions was investigated. The proposed methods could be successfully applied in the concentration range between 5·10^–7 (DPP) or 1·10^–6 (PP) and 5·10^–5 mol/dm³ of alkaloids.     

Determination of the complex formation constants for some water-soluble polymers with trivalent metal ions by differential pulse polarography

The formation of metal complexes between water-soluble polymers, poly(vinyl alcohol) [PVA], poly(N-vinylpyrrolidone) [PVP], poly(acrylamide) [PAAm] and poly(ethylene oxide) [PEO] with trivalent metal ions, Fe³⁺, Cr³⁺, and V³⁺ were studied by using differential pulse polarography (DPP). The general experimental observation is the shift of totally reversible reduction peaks (M³⁺+Hg+e^–M²⁺+Hg) towards more negative potentials when the complexing water-soluble polymers are added to the solution of trivalent metal ions. The negative shift in potential permitted the determination of complex formation constants (K_f) between trivalent metal ions and water soluble polymers. The complex formation constants for Fe³⁺, Cr³⁺, and V³⁺ ions with these polymers increased in the order of V³⁺>Cr³⁺>Fe³⁺.     

Determination of microamounts of neptunium by differential pulse polarography

Neptunium is produced in significant amounts in the “light-water” reactors and must be controlled at different steps of fuel reprocessing. For this purpose, we have developed a method of differential pulse polarography. A tight cell containing 10 ml solution is set up in a Faraday cage. Adjustment to the tetravalent state, Np(IV), is carried out electrochemically on a mercury layer and the Np(IV) concentration is determined by differential pulse polarography, using a dropping mercury electrode. In 0.5M sulfuric acid medium, the redox potential of the reversible couple Np(IV)/Np(III) is-0.3V/SCE. Concentrations as low as 5·10⁻⁷M neptunium can be measured and detection at the 2·10⁻⁷ M level is still possible. (0.5μg in the polarographic cell). Precision is about 2% in the 10⁻⁵M and 10% in the 10⁻⁶M range. The method has been applied to aqueous and organic (TBP_dodecane) solutions. Neptunium can be determined without separation in the presence of plutonium or uranium at M/Np ratios of 10³ and 5·10⁴, respectively. In the presence of fission products a separation is needed.     

A new and direct method for the trace element determination in cauliflower by differential pulse polarography

Using the DPP polarograms of wet digested cauliflower sample in acetate buffer at pH values of 2, 4 and 6, Fe, Zn, Mo, Se, Cr, Cd, Pb, Ti and Cu quantities were determined. The best separation and determination conditions for Zn, Se and Mo was pH 2; for Cr, Zn, Mo and As was pH 4; for Pb pH 6, for Ti, Cu and Fe was pH 6-7 EDTA, for Cd pH 2 EDTA and for lead pH 6, all in acetate buffer. The trace element ranges for cauliflowers from two different seasons were (first figure for winter, the second for summer) for Se 120-250 μg g⁻¹, Fe 70-85 μg g⁻¹, Cu 320-150 μg g⁻¹, Ti 90-120 μg g⁻¹, Cr 130-630 μg g⁻¹, Zn 90-550 μg g⁻¹, Mo 170-230 μg g⁻¹, Cd 20 μg g⁻¹ (in winter) and Pb 130-300 μg g⁻¹ in dry sample. Cd was under the detection limit in summer. The length of digestion time had no effect on the recovery of copper, iron, molybdenum and zinc between 15 and 3 h of digestion.     

Determination of niobium in pyrochlore ore by differential pulse polarography

A differential pulse polarographic method has been developed for the quantitative determination of niobium in pyrochlore ore. One-step polarographic curves were obtained in 0.01 mol L(-1) EDTA as supporting electrolyte. Analytical curves indicated that response was linearly dependent on Nb(V) concentration between 1.6 and 8.6 mg L(-1) in the pH range 2-5. The system is quasi-reversible and controlled by diffusion in 0.01 mol L(-1) EDTA as supporting electrolyte; the electrode process involves one-electron reduction of Nb(V) to Nb(IV). The results obtained so far for niobium in pyrochlore ore were comparable with those obtained by X-ray fluorescence determination. Ions such as Fe(III), Cr(III), As(III), Cu(II), Ni(II), Co(II), Mn(II), Sn(IV), Zn(II), V(V), Ta(V), W(VI), Ce(IV), and Ti(IV) did not interfere. Possible interference from Pb(II) can be avoided by complexation with the supporting electrolyte in the pH range 3.5 to 4.6; Mo(VI) ions can be tolerated when their concentration is one-tenth that of Nb(V).     

Determination of ciclazindol in biological fluids by differential pulse polarography

A differential pulse polarographic method has been developed for determination of the antidepressant, 10-(m-chlorophenyl)-2,3,4,10-tetrahydropyrimido[1,2a]indol-10-ol hydrochloride in plasma and urine. The method involves solvent extraction of the drug from the plasma or urine, evaporation to dryness and dissolution of the residue in 10% methanolic 0.01 M tetraethylammonium chloride solution followed by differential pulse polarography. The mean recovery of the drug from plasma containing 0.5–5.0 μg ml^-1 is 80%; the coefficient of variation is 5.5% at the 1.0-μg ml^-1 (2.98 × 10^-6 M) level on 2-ml samples. The method is not subject to interference from the chemical degradation products and metabolites. The techniques described have been applied to the analysis of human plasma; the polarographic and gas Chromatographic results showed good agreement.