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PubMed1987

[The determination of the coccidiostat nicarbazin in animal tissue and eggs. I. Determination by pulse polarography and high pressure fluid chromatography with electrochemical detection].

The determination of nicarbazin residues in foodstuffs of animal origin by two different methods, polarography, HPLC with electrochemical detection, is described. By applying pulse polarography at the dropping mercury electrode to acetonitrile extracts of animal tissues and eggs, a detection limit of 50 micrograms/kg and mean recoveries of 79% were obtained. The same extracts were used for the HPLC determination with electrochemical detection. This led to a detection limit of 1 microgram/kg. Additional rapid confirmation can be obtained from HPLC using an internal standard (nifursol) and comparing peak area proportions of both substances at varied polarization voltages. The quantitative determination of nicarbazin in chicken eggs by both polarography and HPLC was found to be in good agreement.

Animals↗
PubMed1991

Assay of liver cytosol lipoxygenase by differential pulse polarography.

Lipoxygenase activity assayed by differential pulse polarography was found to be more sensitive than that determined by the increase in absorption at 234 nm. The lipoxygenase activity level in the liver cytosol of rats fed oxidized palm oil was significantly higher than that of the control animals fed either saline or fresh palm oil. The effects of flavonoids on the inhibition of lipoxygenase activity level in liver cytosol of rats were in the decreasing order quercetin greater than myricetin greater than morin greater than phloretin. The observed free malonaldehyde (MDA) in liver cytosol of rats determined by high-performance liquid chromatography using malonaldehyde-dinitro-phenylhydrazine complex was 23, 25, and 51.2% for rats fed saline, fresh palm oil, and oxidized palm oil, respectively. A linear relationship between the lipoxygenase activity and the free liver cytosol MDA was shown. The assay of lipoxygenase by differential pulse polarography provides a simple, sensitive, and quantitative method for the study of liver lipid peroxidation.

Animals↗
PubMed1979

Study of cytochromes c3 from Desulfovibrio vulgaris (Hildenborough) and Desulfovibrio desulfuricans (Norway) by differential pulse polarography and spectroelectrochemical method.

(1) Cytochromes c3 from Desulfovibrio vulgaris (Hildenborough strain) and Desulfovibrio desulfuricans (Norway strain) have been studied by differential pulse polarography and spectroelectrochemical method. Both cytochromes exhibit two reduction potential values Eh approximately --0.25 and --0.34 V (D. vulgaris), Eh approximately --0.16 and --0.34 V (D. desulfuricans). (2) Titrations by dithionite and controlled potential electrolysis coupled with polarography and spectrophotometry suggest that in both cases electronic exchanges are rapid.

Cytochromes↗
PubMed1973

Polarography of polynucleotides. 3. Polyadenylic acid: the electrode process and interaction with polyamines.

Polyadenylic acid (poly A) was studied under various conditions using both DC polarography and phase sensitive AC polarography and by measuring the time-course of the current during the lifetime of a single drop of the dropping mercury electrode. Under certain conditions the current at potentials of the limiting portion of the DC polarographic wave does not reach its limiting value and in extreme situations peak-shaped curves are observed. This phenomenon is explained in terms of desorption and repulsion from the electrode of neutral poly A due to its polyanionic character. Consequently, the suppression of the current can be enhanced by increasing negative potential of the electrode and by exposing the negative charges of phosphate groups, e.g., by increasing pH and temperature and by decreasing ionic strength and buffer capacity; vice versa, the current suppression can be at least partially eliminated by reversing these conditions. Polyamines which seem to shield the phosphate groups through specific interactions are very effective in eliminating the current suppression. The effectiveness of a polyamine is determined by its chain length and by the density of its amino groups and the geometry of their distribution.

Adenine Nucleotides↗
PubMed1988

Choroidal blood flow measured in the dog eye in vivo and in vitro by local hydrogen clearance polarography: validation of a technique and response to raised intraocular pressure.

Local choroidal flow has been measured using hydrogen (H2) clearance polarography in dog eyes in vivo and in vitro. The accuracy and reproducibility of the method was checked in the eye in vitro by demonstrating a linear relationship between flow measurements obtained by an absolute method and those obtained by the H2 clearance technique. The H2 electrode was placed through a scleral window and its current response to a bolus injection of H2-saturated saline into a proximal artery was measured. The clearance of H2 from the choroidal circulation in vitro was monoexponential and the reproducibility of the measurements at the same site and in the same eye was good. In vivo the technique was used to measure alterations in local choroidal blood flow produced by acute changes of intraocular pressure. A linear relationship between perfusion pressure and choroidal blood flow was obtained. H2 clearance polarography is shown to be an accurate and reproducible method for determining choroidal flow, with the advantage that localized repeated measurements of flow can be made.

Animals↗
PubMed1977

Fundamental comments on cell polarography according to Velazquez and Rosado.

Some fundamental comments are made on cell polarography according to Velázquez and Rosado (Fertil Steril 23:562, 1972). The results which they have obtained cannot be reliable because fundamental mistakes are made against the principles of the electroanalytic techniques used. We comment upon the conductometry, the amperometric titrations, and the alternating-current polarography as carried out by Velázquez and Rosado.

Electrophysiology↗
PubMed2003

[Determination of tin in canned foods with oscillographic polarography].

OBJECTIVE: To develop an oscillographic polarography method for determining the concentration of tin in canned foods. METHODS: Because the sensitive polarography wave of tin can be obtained in the system of H2SO4-KI-VitC- NH4VO3, the tin content of several canned foods was analyzed. RESULTS: The detection limit was 0.12 microgram/L. The calibration graph of Sn was linear from 0 to 2.0 micrograms/ml, and the relative standard deviation ranged from 4.22% to 8.33%. The recoveries were 94.7%-112.0%. The samples were analyzed by the proposed method and standard method. The results of the two methods agreed well. CONCLUSION: This method is simple, quick and almost free from interference, and it is available for use in analysis of the canned sample.

Food Contamination↗
PubMed1985

Polarography of cytochrome c in ammoniacal buffers containing cobalt ions. The effect of the protein conformation.

Catalytic currents yielded by cytochrome c in ammoniacal buffers containing cobalt ions at a dropping mercury electrode (Brdicka's catalytic currents) were investigated by means of direct current, differential pulse, normal pulse (NP) and phase-selective alternating current polarography. It was found that Brdicka's catalytic current of cytochrome c, (the more negative part of Brdicka's double wave, wave B) is influenced by the presence of cytochrome c denaturants in the background solution. The wave B rose with the increasing concentrations of urea and sodium perchlorate, and increased in parallel with absorbance changes at 409 and 695 nm measured for identical cytochrome c solutions. The latter absorbance changes reflect unfolding of cytochrome c molecules in the bulk of solution by these denaturants. The results of NP polarography (a technique working with large potential excursion during the drop lifetime) indicate that in Brdicka's solution cytochrome c could extensively be unfolded due to its adsorption at the mercury electrode, polarized to potentials around that of zero charge.

Ammonia↗
PubMed1979

Measurement of bismuth in bone by pulse polarography with anodic stripping voltammetry. Application to two cases of arthropathy.

Pulse polarography with anodic stripping has shown the presence of very high levels (2 005 microgram/kg and 6 760 microgram/kg) of bismuth in bone of two patients treated with bismuth, one parenterally and the other orally. The presence of high levels of bismuth in bone of these patients must be considered in the etiology of their athropathies. Pulse polarography with anodic stripping now permits very precise measurement of bismuth impregnating bones.

Aged↗
PubMedDate not supplied

[Use of alternating-current polarography for determining the lead and cadmium content of wheat grain].

The authors studied the possibility of determining lead and cadmium in wheat grain by polarography in the presence of O. 1 N hydrochloric acid. The determination of lead and cadmium in the grain can be performed with the use of the addition method and the calibrating curve. However, during cadmium determination, the calibrating curve provides more reproducible results. Altogether 100 samples of wheat grown in different regions of the European part of the USSR were analyzed by polarography. The data obtained indicate that the content of lead and cadmium in wheat grain does not depend on the region where that culture was grown. It amounts to 0-0.2 micrograms/g for lead and 0-0.04 micrograms/g for cadmium for the majority of samples. If the content of these elements is higher than the amounts indicated, there is every reason to suggest that in this region there are sources of grain contamination with lead and cadmium.

Cadmium↗
PubMed1983

[Value of the assay of bone aluminum by pulse polarography].

Pulse polarography has been applied to the determination of aluminium in bone. The sensitivity, selectivity and reproducibility of the method are described. The results of bone aluminium concentrations in controls and in haemodialysed patients treated with aluminium compounds are discussed. Pulse polarography permits very precise measurements of aluminium impregnating bone.

Adult↗
PubMed1982

[Measurement of aluminium in bone by pulse polarography (author's transl)].

Pulse polarography has been applied to the determination of aluminium in bone. The sensitivity, selectivity and reproducibility of the method are described. The results of bone aluminium concentrations in controls and in haemodialysed patients treated with aluminium compounds are discuted. Pulse polarography permits very precise measurements of aluminium impregnating bone.

Adult↗
PubMedDate not supplied

[Oscillographic polarography of the alkaloid dolicotheline and several related imidazole derivatives].

Oscillographic polarography in an alkaline medium has shown that the alkaloid N-isovalerylhistamine appears as an expressive wave of the adsorption character in the cathode portion of the curve. This makes it possible to detect it at concentrations up to 10(-6) g/ml. Histamine, histide, isovaleric acid, N-acetylhistamine and imidazole produce no such an effect. A definite correlation has been noted between the toxic action of the compounds studied and their behavior on a mercuric drip electrode during oscillographic polarography. In the alkaline medium the neurotoxic compounds manifest themselves by an adsorption wave in the cathode portion of the curve, while the structurally related compounds (not toxic) do not produce such an effect.

Alkaloids↗
PubMed1980

[Investigations on ashing of animal tissues for the determinations of trace metals by means of polarography or atomic-absorption spectrometry (author's transl)].

A comparison has been made of three ashing methods for animal tissues with subsequent determination of minute quantities of metals by polarography or atomic-absorption spectrometry. Wet oxidation method with many disadvantages and few advantages has been shown not to be useful for the purpose. Both dry ashing in a muffle-furnace at 530 degrees C and low-temperature ashing are equally applicable to atomic-absorption spectrometry, but dry ashing in a furnace is more excellent with polarography. For obtaining ashes with constant compositions it is far more difficult with low-temperature ashing than with dry ashing in a furnace. Hence, dry ashing in a furnace is most widely applicable.

Animals↗
PubMed1996

Use of 2,4-dinitrophenylhydrazone of glyoxylic acid for the determination of glyoxylic acid by the chromatographic-spectrophotometric method and by differential pulse polarography.

Two different methods (one based on chromatography and spectrophotometry and the other on polarography) have been developed for the determination of glyoxylic acid in the form of a derivative with 2,4-dinitrophenylhydrazine (DNPH. GA). The TLC method allows the separation of two DNPH. GA isomers ("trans" and "cis"). Spectrophotometric measurements of the eluents of the separated compounds (lambda=360 nm) allow the determination of GA within the range from 4 to 30 microg. Using differential pulse polarography, the conditions of DNPH. GA formation were examined. The reduction peak of this derivative (E(P)=-0.430 V), observed by dpp, was used to develop a polarographic determination of GA within the concentration range from 1.10(-4) to 7.10(-4) mol/l.

Journal Article↗
PubMed2007

Drug release from differently structured monoolein/poloxamer nanodispersions studied with differential pulse polarography and ultrafiltration at low pressure.

Aqueous colloidal monoolein/poloxamer dispersions are under investigation as drug delivery systems. Depending on the composition and preparation procedure these dispersions may either contain predominantly vesicular particles or nanoparticles of cubic inner structure. To study the influence of ultrastructure on drug release, corresponding dispersions loaded with the model drugs diazepam (two different concentrations) and chloramphenicol were prepared by high-pressure homogenization with or without subsequent heat treatment. The dispersions were characterized with regard to particle size and their ultrastructure was confirmed with small angle X-ray diffractometry. Two techniques with high time resolution, differential pulse polarography (DPP) and ultrafiltration at low pressure were compared for their suitability to monitor rapid release from the dispersions. Instantaneous release was found for both drugs independent on the type of particle structure with the amount of released drug being controlled by the partition coefficient. Both release methods were suitable to monitor the rapid appearance of the releasable drug in the release medium.

Chloramphenicol↗
PubMed1976

Determination of nitroimidazoles in biological fluids by differential pulse polarography.

A sensitive differential pulse polarographic assay was developed for the determination of metronidazole, ornidazole, and 2-nitro-1H-imidazole-1-(3-methoxy-2-propanol) in plasma. The compounds are selectively extracted into ethyl acetate from a protein-free filtrate of plasma, buffered to pH 7.0 +/- 0.2. The residue of the ethyl acetate extract is dissolved in 0.1 N NaOH and analyzed by differential pulse polarography for the reduction of the nitro group at approximately -0.600 v versus the saturated calomel electrode. The overall recovery from plasma was about 55 +/- 3.0% (SD) for the three compounds investigated. A TLC step after the ethyl acetate extraction may also be included to ensure specificity. This step reduced the overall recovery to approximately 45%. The sensitivity limit of detection from plasma using a 2-ml sample is 0.1 mug/ml. The assay may also be employed for the analysis of urine. The urine is adjusted to pH 7.0 +/- 0.2 and extracted with ethyl acetate, and the residue is analyzed as described for plasma. The assay was applied to the determination of ornidazole in blood and urine in the dog following 10 mg/kg po.

Animals↗
PubMed1977

Simultaneous determination of 4-nitroanisole, 4-nitrophenol, and 4-nitrocatechol by phase-sensitive ac polarography.

Phase-sensitive ac polarography was applied to the simultaneous quantitative determination of 4-nitroanisole, 4-nitrophenol, and 4-nitrocatechol in alkaline solutions. Certain experimental precautions are necessary to determine each compound in the presence of the other two. Thus, 4-nitrocatechol is determined indirectly by forming a yellow ratio chelate with cupric ions, wheras 4-nitroansole is determined directly by the reduction waves of the nitro group. For the determination of 4-nitrophenol, the interferency by the simultaneously present 4-nitrocatechol must be eliminated by masking it by the addition of magnesium ions. The method described permits a qualitative and quantitative analysis of all three compounds in one solution since linear calibration curves are obtained.

Anisoles↗