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Stannous salts are used as reducing agents in many radiopharmaceutical kits. Differential pulse polarography, with 1 M sulfuric acid as the supporting electrolyte, is a relatively simple and effective technique for stannous quantitation and can be used in the quality assurance testing of pyrophosphate and polyphosphate radiopharmaceutical kits.
The electrode processes for the reduction of several tetracyclines by ac polarography were examined. In pH 4.0 Walpole acetic acid-acetate buffer, two main waves occurred; the first was quasireversible and the second was reversible. Results showed that the first wave can readily be used for quantitative work. The second wave would also be suitable provided that there was no interference from other electroreducible substances.
During the study of the temporal changes of benzylpenicillenic acid in aqueous buffers using differential pulse polarography, penicillamine was found to be a degradation product at neutral pH. Since this result was not previously reported, the effects of pH and buffer concentration on penicillamine formation were investigated. The amount of penicillamine produced was greatest under conditions producing maximum benzylpenicillenic acid stability. Penicillamine was not obtained from benzylpenicilloic acid, the reported degradation product of benzylpenicillenic acid at neutral pH. Penicillamine also was detected in penicillin G solutions of neutral pH. Therefore, it is suggested that penicillamine found in penicillin G solutions arises from benzylpenicillenic acid degradation which, in turn, is produced from penicillin G isomerization. A pathway is proposed to show that penicillamine originates from the UV-absorbing isomer of benzylpenicillenic acid.
A differential pulse polarographic method for the determination of fluoxymesterone, norethandrolone, prednisolone, and prednisone in tablets is described. This method is more sensitive than dc polarography, and the measurement of diffusion current is greatly simplified. Sørensen phosphate buffer, pH 5.6, was used as the supporting electrolyte. No apparent interference was observed from tablet excipients; the method is rapid, simple, and relatively precise.
A simple and convenient method for the routine determination of clonazepam in tablets by dc polarography is described. Clonazepam is extracted from the sample by ethanol and diluted with pH 4.15 acetate buffer in a volumetric flask. The filtered solution is then polarographed at the dropping mercury electrode versus the saturated calomel electrode. The polarographic wave is well developed; the determination is quantitative, precise, and accurate.
A sensitive and reproducible differential pulse polarographic method of analysis was developed for indicine-N-oxide (NSC 132319) in human plasma. Lyophilized plasma is extracted with methanol, and the extract is chromatographed over partially deactivated aluminum oxide and reversed-phase silica gel columns. Indicine-N-oxide is eluted from the silica gel column with 25% aqueous methanol and quantitated by differential pulse polarography by measurement of the peak current at -0.72 +/- 0.03 v (versus the saturated calomel electrode). Recovery of indicine-N-oxide from plasma was 88 +/- 7% (SD) in the 1-20-microgram/ml range. The method was linear over the range of 0.5-10 microgram/ml of pH 4.6 buffer.
In an attempt to develop a more rapid, convenient, and precise method for the direct detection and analysis of the degradation products of tetracycline, a study of those products utilizing differential pulse polarography was initiated. The investigation was concentrated on the subject of the kinetics of the epimerization of anhydrotetracycline to 4-epianhydrotetracycline in acetate buffer. The reaction was followed at 25 and 50 degrees. Duplicate experiments were run at each temperature. The apparent rate constants obtained were 4.17 +/- 0.13 X 10(-1)/hr (25 degrees) and 6.97 +/- 1.00 X 10(-2)/hr (50 degrees).
SC-13504 was given intravenously to baboons with photosensitive epilepsy, Papio papio, with and without prior administration of allylglycine. Plasma levels of the drug were determined by differential pulse polarography and correlated with behavioural changes and the anticonvulsant action of the drug. Protection against photically induced seizures or self-sustaining myoclonic responses was seen 30 to 120 min after SC-13504, 4-8 mg/kg (when plasma levels were 1 mug/ml or greater). EEG and neurological signs of toxicity were seen after SC-13504 8 mg/kg but not after 4-6 mg/kg.
The electrochemical reduction of betamethasone valerate (BV) in a pharmaceutical formulation containing neomycin has been carried out in Britton-Robinson buffer (BRB) (0.04 mol L(-1)) by differential-pulse polarography (DPP). BV exhibits a well-defined irreversible reduction peak at -1.03 V/ref. The influence of pH on the reduction of BV was studied in Britton-Robinson buffer (pH range 1.7-10). A method for the analysis of BV in BRB (0.04 mol L(-1)), which allows quantification over the range 3.9x10(-6)-1.1x10(-4) mol L(-1), was proposed and successfully applied to the determination of BV in tablets with mean recovery and relative standard deviation of 100.81% and 0.45%, respectively.
A simple polarographic assay for platinum determination in cis-dichlorodiammineplatinum(II)-DNA complexes is described. The method makes it possible to determine the free (unbound) drug in the presence of DNA or platinum-DNA complex, i.e., without a separation of free drug and macromolecular components of the solution to be analyzed. This method is based on the polarographic activity of intact cis-dichlorodiammineplatinum(II) at -1.5 V, which can be measured by differential pulse polarography even in the presence of DNA or platinum-DNA complex. The lower level of analytical utility of this method is ca. 1 X 10(-6) M (195 ng of platinum/ml).
Two methods to quantify metallothionein (MT), differential pulse polarography (DPP) and radioimmunoassay (RIA), were compared for MT analysis of liver from Zn- and Cd-injected perch (Perca fluviatilis). Nine perch were intraperitoneally injected, twice a week during 2 weeks with ZnSO4 and CdCl2 to yield a total dose of 30 mg Zn and 3 mg Cd per kilogram body weight. Two samples, 100 and 200 mg from each liver, were homogenized separately and further prepared for DPP, RIA, and atomic absorption spectroscopy. MT values obtained by DPP were in good agreement with the MT values determined by RIA (r = 0.92). The relationship between the MT values analyzed with the two methods is described by the formula MTRIA = MTDPP x 0.99-0.048. Analysis of MT was not affected by sample size. MT values from individual liver samples plotted against the Cd and Zn content of the corresponding samples provided a high correlation. The correlation coefficient was 0.86 for MT values obtained by DPP and 0.92 for MT measured by RIA. It is concluded that DPP is a reliable method for analyzing MT in liver.
The oxidation-reduction midpoint potentials (Em) of the following compounds have been measured in the range of pH from 3 to 12 by polarography: methyl viologen; benzyl viologen; 2-hydroxy-1,4-naphthoquinone; 2-hydroxy-1,4-anthraquinone; N,N,N',N',-tetramethyl-p-phenylenediamine; 2,3,5,6-tetramethyl-p-phenylenediamine; phenazine; N-methylphenazonium methosulfate; N-methylphenazonium sulfonate methosulfate; N-ethylphenazonium ethosulfate; pyocyanine; neutral red; safranin; phenol red; chlorophenol red; cresol red; bromocresol purple; 2,5-dibromo-3-methyl-6-isopropylbenzoquinone and 5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole. Many of these previously assumed to have a simple behavior in this range have proven to be rather more complicated, and several anomalous observations have been reconciled.
Regional lingual blood flow was measured by hydrogen polarography under control conditions and after the subsequent ligation of pertinent arteries in dogs. The results indicate a nonhomogeneous blood supply for the tongue and the existence of a complex collateral circulation in the lingual areas studied.
Differential pulse polarography (DPP) was applied to measure metallothionein (MT) content in the RH-35 rat hepatoma cell. The method was sensitive in measuring MT at nanogram concentrations. The MT measurement was not interfered by small molecular weight proteins. Cellular MT content increased upon incubated in medium containing different concentrations of CdCl2 or ZnCl2. The increase was concentration-dependent. In the case of CdCl2, significant increase in cellular MT content was observed at a level as low as 0.18 mg/l. The change in MT occurred when there was no significant change in cell viability or cellular protein content. The concentration of ZnCl2 needed to induce the same amount of MT as that with 0.18 mg/l CdCl2 was 12 mg/l. At high concentrations (> 12 mg/l), ZnCl2 also caused an increase in cellular protein content. Therefore, when calculation was based on cellular protein content, ZnCl2 did not caused further increase in MT. L-ascorbic caused significant increase in cellular MT content when it was presented at levels above 100 mg/l but not at 50 mg/l. The effect of L-ascorbic acid on MT induction was not dose-dependent. At 150 mg/l, the amount of MT induced was not different from that with 100 mg/l. Thus, L-ascorbic might not directly influence cellular MT content. Cysteine at 4 and 40 mg/l did not increase cellular MT content. The results of this study showed that cellular MT content could be measured by DPP. Our finding that CdCl2 at sub-lethal concentrations can effectively induce MT suggests that MT may serve as an early warning signal prior to serve as an early warning signal prior to the occurrence of cell death.
Differential pulse polarography (DPP) and electron spin resonance (ESR) were used to study the influence of substituents and of the pH of the medium on DPP peak potentials (electrochemical reduction) resp. kreduction (chemical reduction) of nitroxyl free radicals. The DPP peak potentials can be used to select the appropriate nitroxide spin label for relevant biochemical and biophysical applications.
The electrochemical reduction of pipamperone has been carried out in aqueous solution in KNO(3) (0.1 mol l(-1)) by differential-pulse polarography (DPP). Pipamperone exhibits a well-defined irreversible reduction peak at -1.3 V/ref. The influence of pH on the reduction of pipamperone was studied in Britton-Robinson buffer (pH range 2-10). A method for the analysis of pipamperone in KNO(3) (0.1 mol l(-1)), which allows quantification over the range 1.6x10(-5)-2.0x10(-4) mol l(-1), was proposed and successfully applied to the determination of pipamperone in tablets with mean recovery and relative standard deviation (R.S.D.) of 100.35 and 0.49%, respectively.
The polarographic behaviors of telmisartan (TE) are investigated in 0.8 mol/l NH3.H2O-NH4Cl (pH = 8.9) supporting electrolyte. The results demonstrated that the reduction peak is obtained at ca. -1.30V, which corresponds to a catalytic hydrogen wave. Based on the catalytic hydrogen wave, a novel method has been developed for the determination of telmisartan by linear sweep polarography. Calibration curve is linear in the range 2.0 x 10(-7) to 3.0 x 10(-6) mol/l and the detection limit is 1.0 x 10(-7) mol/l. The proposed method is applied to the rapid determination of the telmisartan in capsule forms and biological sample without pre-separation.
Differential pulse polarography (DPP) is proposed as a direct method for the quantitation of todralazine and acetazolamide in human serum. The method was applied to the determination of these drugs in human serum, after a liquid-liquid extraction process. This extraction process together with the use of the standard additions method is essential for the elimination of the matrix effect. The proposed method enables detection limits of 0.107 microgram ml-1 for acetazolamide and 0.111 microgram ml-1 for todralazine to be achieved at reduction potentials of -0.59 and -0.86 V, respectively, using Britton-Robinson buffer (pH 1.65) as the supporting electrolyte.