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.

---

Bestimmung von Oxytetracyclin in Urin und Humanserum durch Differential-Pulspolarography

     

Determination of mitomycin C in human blood plasma and urine by high-performance differential pulse polarography

High-performance differential pulse polarography is used for determining the antitumor antibiotic mitomycin C in human blood plasma and urine. The limit of determination (2-ml samples) is 25 ng ml^?1 when the substance is isolated by means of Amberlite XAD-2, and 200 ng mo_?1 when samples are not pretreated. The method was applied in a pharmacokinetic experiment; no metabolites of mitomycin C were observed in urine or plasma.     

Determination of vitamin k1 in plasma by differential pulse polarography and its possible clinical application

Differential pulse polarography, following solvent extraction, is used to monitor the clearance of vitamin K₁ (2-methyl-3-phytyl-1,4-naphthoquinone) from human plasma after a 20-mg intravenous injection. The average recovery of vitamin K₁ added to plasma (200–3000 ng ml^-1) was 72.2%. The coefficient of variation was 3.0% at a concentration of 2.75 μg ml^-1 of plasma. Measurements of vitamin K₁ in plasma from patients given an intravenous injection of the vitamin, support the idea that a metabolic cycle involving vitamin K₁ underlies calcification of bone.     

单扫描示波极谱法测定扑热息痛

扑热息痛与NaNO2在中性介质中发生反应，其亚硝化衍生物具有良好的电活性。在pH9．37的Britton-Robinson缓冲溶液中，于-0．56V(vs．SCE)产生灵敏的极谱还原峰，峰电流与扑热息痛质量浓度在0．007-0．4mg/L范围有良好的线性关系，检测下限为5μg/L。此法已用于测定小儿速效感冒灵。     

Determination of nitrite in foods by single-sweep polarography

In an acid medium, nitrite diazotized with p-rosaniline and then coupled with 8-hydroxyquinoline in a weak alkaline medium produces azo compounds. The azo compounds produce a very sensitive polarographic wave at -0.70 V (versus the saturated calomel electrode). The height of the peak is linear with the concentration of nitrite in the range of 5 x 10(-9) to 5 x 10(-7) g/mL. The detection limit is 3 x 10(-9) g/mL. The electrochemical characteristics of the polarographic wave are also discussed. The method was used to determine nitrite in sausage. The results agree well with those obtained by spectrophotometry.     

Determination of magnesium in foods by single-sweep polarography

In KOH, the Mg(II)-bromopyrogallol red (BPR) complex produced a very sensitive polarographic wave at -1.30 V. The wave height was linear with the concentration of Mg(II) in the range of 0.05 to 2 microg/mL. The detection limit was 0.01 microg/mL. The electrochemical behavior of Mg(II)-BPR was studied by electrochemical and spectrophotometric methods. Experiments proved that the polarographic wave of Mg(II)-BPR was due to the reduction of BPR in the Mg(II)-BPR complex. The method, which was sensitive, selective, and simple to perform, was used to determine magnesium in foods, and the results were consistent with those obtained by atomic absorption spectroscopy.     

Assay of flurazepam in plasma by differential pulse polarography

Analytical and Bioanalytical Chemistry - A combination of differential solvent extraction based on physical chemical properties of the species involved and differential pulse polarography has been...     

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.

---

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.

---

---

On leave from Jadavpur University, Calcutta, India     

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 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 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 ribavirin in human serum and plasma by capillary electrophoresis

The electrophoretic separation of ribavirin and 5-methylcytidine (internal standard) by capillary electrophoresis was examined. Separation was achieved using reverse polarity in a 100 mM borate electrolyte, pH 9.1, with 5 mM spermine added to reduce the electroosmotic flow. Sample preparation based on acetonitrile protein precipitation was found to be unsuitable for ribavirin analysis in patient samples due to insufficient sensitivity and interferences. Solid-phase extraction employing phenyl boronic acid cartridges provided cleaner separations. Using this approach with 500 microL sample and reconstitution of the dried extract into 100 microL of 33% v/v 100 mM phosphate buffer, pH 6.4 / 67% v/v acetonitrile, the detection and quantitation limits were determined to be 0.05 and 0.10 microg/mL, respectively, a sensitivity that is suitable for therapeutic drug monitoring of ribavirin in human plasma and serum samples. The method was validated and compared to a high-performance liquid chromatography (HPLC) method, showing excellent agreement between the two for a set of samples that stemmed from patients being treated with ribavirin and interferon-alpha-2b for a hepatitis C virus infection.     

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 trace thiocyanate by linear sweep polarography

In a thiocyanate solution containing iron (II), nitrite and ascorbic acid, a linear-sweep polarographic wave appears at ?0.42 V (vs. SCE). In anodic sweeps, the derivative peak current is directly proportional to the concentration of thiocyanate over the range 2×10^?8?1×10^?6 M; the detection limit is 1×10^?8 M. The procedure is used for the determination of trace thiocyanate (10^?3?10^?4 M) in saliva. The mechanism of the electrode process is discussed; the polarographic wave is ascribed to catalytic reduction of dissolved oxygen in the presence of an adsorbed ternary Fe/SCN/NO complex.     

Determination of cadmium in uranium by ion exchange and square-wave polarography

Traces of cadmium in uranium and its compounds can be determined by ion-exchange separation and square-wave polarography. With a small column of anion-exchange resin, cadmium can be separated from uranium and recovered quantitatively from hydrochloric acid solution, Separations of cadmium from uranium are not perfect but are sufficient for the determination of traces of cadmium by square-wave polarography. The lower limit of the method is 0.01 p.p.m. of cadmium.     

Determination of manganese in uranium by ion exchange and square-wave polarography

Traces of manganese in uranium and its compounds can be determined by ion-exchange separation and square-wave polarography. When a 9 M hydrochloric acid solution of the sample is introduced into a column of strongly basic anion-exchange resin, manganese can be quantitatively separated from uranium by cluting with 9 M hydrochloric acid. The determination of the separated manganese by square-wave polarography is performed in 1 M potassium hydroxide-0.4 M triethanolamine solution with an excellent sensitivity. The lower limit of the method is 0.5 p.p.m. of manganese.