The polarographic estimation of steroid hormones: 2. Polarography of related steroid hydrazones.
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Journal Article↗
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[Determination of urocanic acid. II. Polarography, adsoprtion on activated charcoal, precipitation with mercuric salts, and anion-exchange chromatography in urine analysis].
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Acrylates↗
Potential carcinogenicity of the synthetic 1,3,6-triazine (6-aza) nucleic acid analogues determined by DC polarography. I. Nucleobases.
The polarographic reduction of several synthetic 1,3,6-triazine (6-aza) nucleobases in the strictly anhydrous solution was studied in the absence and presence of alpha-lipoic acid. The values of the half-wave potentials E1/2 and the parameter of potential carcinogenicity tg alpha were determined for one natural and 5 synthetic nucleobases. The current value of the first diffuse polarographic wave or a new diffuse polarographic wave belonging to the nucleobase-alpha-lipoic acid complex increased with the increased alpha-lipoic acid concentration for the all compounds only marginally. Although this diffuse current increase was linearly depended on the alpha-lipoic acid concentration in anhydrous solutions, the determined index tg alpha values ranging between 0.029 and 0.108 indicated a very low potential carcinogenicity of the all nucleobases investigated.
Aza Compounds↗
Polarographic determination of flutamide.
The polarographic reduction of flutamide was investigated by direct current polarography (DCP), alternating current polarography (ACP), normal pulse polarography (NPP) and differential pulse polarography (DPP). The supporting solution was phosphate buffer containing 5% of 95% ethanol. The reduction process at the dropping mercury electrode was diffusion controlled and irreversible. Extraction with 95% ethanol followed by polarographic reduction was selected as the basis of a method for the determination of flutamide as a pure compound and in tablets.
Electrochemistry↗
Differential pulse-polarographic analysis of tobacco mosaic virus.
The tobacco mosaic virus (TMV) strain vulgare and its mutant TMV 483 (with glutamine-9 replaced by histidine) and the denatured protein of TMV vulgare were analysed by direct current (d. c.) and differential (derivative) pulse polarography (DPP) in the basic electrolyte composed of 0.001 M Co(NH3)6Cl3, 0.1 M NH4Cl and 0.1 M NH3 at 0 degrees C. The DPP method gave a substantially better resolution of the polarographic catalytic maxima A and B, but a much lower resolution of the maxima B and C, as compared with the d. c. polarographic method. The clear differentiation of the maximum A from maximum B by DPP permitted to study the variation of maximum A in the course of alkaline degradation of TMV. But for the study of TMV protein denaturation the d. c. polarography is preferable, because the denaturation is accompanied by the appearance and rise of maximum C which can be clearly differentiated from maximum B by d. c. polarography rather than by DPP. The DPP method was more, sensitive than d. c. polarography. The denatured TMV protein can be determined by DPP at concentrations around 0.1 microgram/ml.
Histidine↗
The voltammetric study and determination of ramipril in dosage forms and biological fluids.
The voltammetric behavior of ramipril was studied using cyclic voltammetry, direct current polarography (DCt), differential pulse polarography (DPP) and alternating current polarography (ACt). Ramipril developed well-defined cathodic waves in Britton-Robinson buffers over the pH range 6-12. The waves were characterized as being diffusion-controlled, irreversible and partially affected by adsorption phenomenon. The diffusion-current constant (Id) was 1.24 +/- 0.02. The current-concentration plots were rectilinear over the range 10-50, 4-40 and 0.16-12 micrograms/ml in the DCt, DPP and ACt modes, respectively, with a minimum detectability (S/N = 2) of 0.02 microgram/ml (4.8 x 10(-8) M) using the latter mode. The proposed method was successfully applied to the determination of ramipril in commercial tablets. Hydrochlorothiazide, which is frequently co-formulated with ramipril, did not interfere with the assay. Furthermore, the proposed method was applied to the determination of ramipril in urine and plasma adopting the ACt technique. The percentage recoveries were 97.12 +/- 0.56 and 94.97 +/- 0.62%, respectively. A pathway for the electrode reaction was proposed.
Angiotensin-Converting Enzyme Inhibitors↗
Electrochemical study of cefetamet-Na and its polarographic determination.
Polarographic behavior of cephalosporin cefetamet-Na (Cef-Na) in aqueous solutions of pH ranging from 1.7 to 12.5 was investigated by applying direct current (dc) polarography, differential pulse polarography (dpp), alternating current (ac) polarography, cyclic voltammetry and electrolysis at constant potential. The characteristics of the corresponding electrode reaction are presented and discussed. The electrode reaction was found to be affected by strong adsorption, strongly and slightly pronounced in acidic and alkaline media, respectively. The methoxyimino group electroreduction was carried out and the mechanistic scheme was suggested. In addition, a sensitive dpp method was proposed for analytical determination of a very low concentrations of Cef-Na.
Ceftizoxime↗
A search for nitrosamines in East African spirit samples from areas of varying oesophageal cancer frequency.
Following the report of the presence of nitrosamine-like substances in samples of homemade spirit from Zambia, which had been obtained from an area where cancer of the oesophagus is common, samples of distilled alcoholic drinks were collected throughout western Kenya and southern Uganda from areas where the frequency of cancer of the oesophagus varies from very common to very rare. The 44 samples of spirit were screened by polarography and substances giving a similar response to nitrosamines were indicated at levels as high as 21 ppm. Subsequent analysis by gas chromatography for selected individual nitrosamines showed no evidence for the occurrence of methylethylnitrosamine (MEN), diethylnitrosamine (DEN), dipropylnitrosamine (DPN), ethylbutylnitrosamine (EBN), dibutylnitrosamine (DBN), nor of N nitrosopiperidine (N Pipn), but traces of compounds having a similar retention time as dimethylnitrosamine (DMN) were observed. However, subsequent examination by mass spectrometry showed no evidence of dimethylnitrosamine. There was no apparent association between the levels of unknown constituents indicated by polarography and gas chromatography, nor between either of these levels and the frequency of cancer of the oesophagus. The results by gas chromatography and mass spectrometry confirm that polarography is too unspecific to be a useful indicator of nitrosamines.
Alcoholic Beverages↗
[Pharmaceutical and biopharmaceutical evaluation of acetylaminonitropropoxybenzolum (Falimint). 3: Polarographic analysis and determination of active agents].
According to its aromatic nitro group acetylaminonitropropoxybenzene (Falimint) can be determined polarographically. The typical behavior of the nitro group becomes evident by the elektrochemical reduction. The investigation has shown two phases of reduction with pH-depended half-wave-potential shifts, so that a two-step mechanism is conceivable. Using direct current polarography the substance is determined in a concentration range from 1 to 100 micrograms/ml. Low elektroaktive background signals within the potential range the four-electron reduction step are the basis for the determination of the active agent in saliva, urine and blood plasma without any extracting procedures. It is possible to identify the substance by means of oscilloand square-wave-polarography. The resulting polarogrammes are typically for the p-nitrophenyl structure. Further a new quantitativ polarographic method, named sample-DC-polarography on the stationary mercury electrode is discussed for the determination of Falimint in blood plasma without any steps of separation and cleaning in the concentration range of 0,1-3,0 micrograms/ml.
Acetanilides↗
Electroreduction of nifedipine.
At pH greater than 6, the nitro group of nifedipine is reduced in a four-electron step to a hydroxylamino group. At pH less than 6, the hydroxylamino derivative undergoes an acid-catalyzed dehydration, and the rate of this reaction governs the limiting current. Resulting quinonemethide is further reduced, and a six-electron reduction step results. Formation and reducibility of the quinonemethide is favored by conjugation with the 1,4-dihydropyridine ring. Further reduction of the hydroxylamino derivative is confirmed by the absence of the anodic oxidation peak on the reverse scan at pH less than 6.5. At potentials more negative than that of the nitro group, the protonated form of the hydroxylamino derivative is reduced between pH 4 and 8 in direct current (dc) polarography and between pH 6 and 11 in cyclic voltammetry, the difference resulting from the difference in the measurement time window. The yields and fate of the hydroxylamino derivative obtained in controlled potential electrolysis with a hanging mercury drop electrode (HMDE) differ from those in dc polarography, indicating the presence of different competing reactions. For analyses, pH 2 and 11 are most suitable.
Electrochemistry↗
On the safety evaluation of extracts from synthetic polymers used in medicine.
The methods of oscillographic polarography and pulse differential polarography were used to test the release of some contaminating substances from polyvinylchloride (PVC) during autoclaving of water suspensions. The polarographic technique was able to detect in some extracts the presence of several contaminants, while the other PVC preparations did not release such substances. However the chemical nature of the contaminating substances has not been elucidated, the methods can serve as a screening method to detect heavy polymer contamination.
Oscillometry↗
Electrochemical behavior and differential pulse polarographic determination of piperacillin sodium.
In an aqueous piperacillin sodium solution, a well-defined single wave or single peak was observed by direct current (DC) polarography or differential pulse polarography (DPP). The peak potential change per pH unit was -54 mV in the phosphate buffer at 18 degrees C, which indicated that protons were involved in the electrochemical reduction of the 2,3-dioxopiperazine moiety of piperacillin sodium with a H+/e- ratio of one. Using a phosphate buffer of pH 4.3, the 1.0 x 10(-7) M piperacillin sodium single peak could be determined by DPP with relative standard deviation of 1.6% (n=3). Piperacillin sodium could be analyzed without interference from penicillin G-potassium, which enabled the employment of DPP as a fast and simple technique for monitoring the synthetic process of the antibiotic.
Calibration↗
Anti-oxidant and pro-oxidant effects on nerve conduction velocity, endoneurial blood flow and oxygen tension in non-diabetic and streptozotocin-diabetic rats.
Increased oxygen free radical activity, coupled with reduced protection against oxidative stress, could play a role in the aetiology of neurovascular abnormalities in experimental diabetes mellitus. To test this hypothesis, non-diabetic and streptozotocin-diabetic rats were treated with the anti-oxidant probucol or the pro-oxidant primaquine. One-month diabetes caused 21.4% and 13.6% reduction in sciatic motor and saphenous sensory conduction velocity (p < 0.001). These deficits were prevented by probucol treatment (p < 0.001). After 1-month untreated diabetes, conduction velocity deficits were reversed by a further month of probucol treatment (p < 0.001). For non-diabetic rats, primaquine treatment caused a 12.9% reduction in motor conduction velocity (p < 0.001), which was prevented by probucol treatment (p < 0.001). Primaquine treatment did not affect diabetic rats. Sciatic nerve nutritive endoneurial blood flow, measured using microelectrode polarography and hydrogen clearance, was 48.0% reduced by 2-month diabetes (p < 0.001). This was completely prevented by probucol treatment (p < 0.001). Primaquine treatment did not affect blood flow in diabetic rats. However, in non-diabetic rats it caused a 30.0% reduction (p < 0.01) which was prevented by probucol treatment (p < 0.05). Sciatic endoneurial oxygen tensions were also measured by microelectrode polarography. Mean tension was 38.8% reduced by diabetes (p < 0.001). This was prevented by probucol treatment. Non-diabetic rats given primaquine treatment showed a 21.7% reduction in endoneurial oxygen tension (p < 0.01). The data suggest that vascular-mediated nerve dysfunction in diabetes depends on oxidative stress, and that similar effects in non-diabetic rats may be produced by pro-oxidant treatment. This provides evidence for the potentially important role of oxygen free radical activity in diabetic neuropathy.
Animals↗
Polarographic study on poly alpha-L-glutamic acid-Cd2+,Co2+ complexes in the helix-coil pH region.
Interactions between poly alpha- L-glutamic acid (PGA) and metal ions Cd(2+), Co(2+) were studied by direct current polarography. The diffusion currents of these ions decreased sharply in the presence of PGA in the pH region from 5.0 through neutral. A corresponding increase in the helix content of the PGA-metal ion complex was revealed by CD measurements on the same solutions. Helix contents determined by polarography were in good agreement with those by CD in the neutral pH region. On the contrary, the decrease of current in lower acidic pH regions was independent of helix formation and suggested that metal ions coordinate to sporadically-dissociated carboxylate groups to cause aggregation of the intra and/or inter polymer chains. The diffusion current of the ions, therefore, is a parameter sensitive to the conformational changes of PGA from acidic through neutral pH region.
Biopolymers↗
Single-sweep polarographic investigation of concanavalin A and its interaction with polysaccharide.
A simple, rapid, and sensitive single-sweep polarographic method has been developed for investigation of concanavalin A (con A) and its interaction with selected polysaccharides. In a solution containing 0.001 M 2,2'-bipyridine, 0.015 M hexamethylenetetramine, and 0.1 M sodium chloride, con A exhibits a single-sweep polarographic wave, and the cathodic peak potential is -1.50 V (vs SCE). The peak current varies linearly with con A concentration over a range of 1.0 x 10(-8) to 1.2 x 10(-7) M by derivative single sweep polarography. A preliminary discussion on properties of the con A polarographic wave has been made. In addition, it has been demonstrated that single sweep polarography can be a useful method for studies on interactions of con A with its complementary polysaccharides in solution.
Concanavalin A↗
Iminodiacetate complexes of technetium: an electrochemical study.
Iminodiacetate complexes of technetium are used extensively in diagnostic medical imaging, but their chemical structure and properties are yet uncertain. We studied formation of technetium-99 complexes with diethylenetetraminepentaacetate (DPTA), ethylenediaminetetraacetate (EDTA), N-(2-acetamido)iminodiacetate (ADA), and N-(2,6-dimethylphenylcarbomoylmethyl)iminodiacetate (HIDA) by tast (sampled DC) polarography, reverse-pulse polarography, controlled-potential coulometry, and amperometric titration. The products, often mixtures, varied with reaction conditions and ligand; this can explain apparent contradictions in previous studies.
Edetic Acid↗
Differential pulse polarographic assay of tolmetin sodium capsules.
Differential pulse polarography (DPP) is proposed as a direct method for the quantitation of tolmetin sodium in a capsule formulation (Tolectin--200 mg as the sodium dihydrate salt). Classical direct-current (DC) polarography has been employed to investigate the nature of the reduction occurring at the surface of the dropping mercury electrode (DME) using acetate buffer of pH 5.0 as the supporting electrolyte. The mean value of the results obtained by DPP expressed as a percentage of the stated amount, and the standard deviation, were found to be 99.87 +/- 0.43. The standard addition procedure used to assess the accuracy of the proposed method gave a mean percentage recovery of the total drug of 100.15 +/- 0.75%.
Capsules↗
Anodic polarographic determination of josamycin in formulations and spiked human urine.
The anodic polarographic behaviour of josamycin (a macrolide antibiotic) has been studied using direct current (DC(t)) polarography and differential pulse polarography (DPP). In Britton-Robinson buffers (BRb) josamycin exhibited well-defined anodic polarographic waves in the pH range 2-8. In BRb of pH 6, the diffusion-current constant was 1.62 microA mmol(-1) (n = 6). The current-concentration plots are rectilinear over the range 10-50 and 5-40 microg/ml using the DC(t) and DPP modes, respectively, with a detection limit of 4.83 x 10(-6) M adopting the DPP mode. The method was applied to commercial tablets adopting both DC(t) and DPP modes, the recoveries % were 99.13 +/- 2.22 (n = 10) and 99.82 +/- 1.82 (n = 7), respectively. The method was further extended to the in vitro determination of josamycin in human urine, the recovery % (n = 6) was 100.06 +/- 2.84. The number of electrons involved in the electrode process could be accomplished and a proposal of electrode reaction was presented.
Aldehydes↗