Voltammetric determination of papaverine and drotaverine

Isoquinoline derivatives (papaverine and drotaverine) are oxidized at a graphite electrode in a 0.1 M sulfuric acid solution to give voltammetric waves at 1.1 V for papaverine and at 1.05 and 1.28 V for drotaverine. Determination limits and linearity ranges of currents as functions of papaverine and drotaverine concentrations are estimated. Microgram amounts of papaverine and drotaverine are determined in model solutions (RSD = 1–4%). A procedure for the direct determination of papaverine and drotaverine in pharmaceuticals is proposed.     

Potentiometric Determination of Ascorbic Acid: Estimation of Its Contribution to the Total Antioxidant Capacity of Plant Materials

It was found that an iodine-modified platinum electrode gives a linear potentiometric response to 1.0 × 10^–5 to 1.0 × 10^–3 M ascorbic acid in model solutions. Ascorbic acid in some preparations was determined by potentiometry. The contribution of ascorbic acid to the total antioxidant capacity of aqueous extracts of hips, hop cones, and lemon juice was estimated.     

Synthesis of thiadiazabicyclane and bis-1,3,5-dithiazinane by cyclothiomethylation of aliphatic diamines with CH2O and H2S

Cyclocondensation of aliphatic diamines with CH₂O and H₂S (1:3:2 ratio, 0 °C) was carried out to give thiadiazabicyclanes and dithiadiazabicyclanes (1:6:4 ratio), which were previously difficult to synthesize. Symmetric α,ω-bis-1,3,5-dithiazinanes were synthesized at 80 °C by this reaction. The stereochemistry of thiadiazabicyclanes was assigned by ¹H and ¹³C NMR spectroscopy and by theoretical DFT calculations, and of bis-dithiazinanes by X-ray diffraction study in the solid state.     

Use of galvanostatic coulometry in the analysis of arbidol drug

Arbidol is proved to easily and completely react with electrogenerated bromine in the ratio 2: 9; so procedures for the arbidol quantification in the neat substance and drugs are developed, the RSD value does not exceed 2%. A procedure for the coulometric determination of water in the arbidol substance using the Fisher method is proposed.     

Reactions of phenolic antioxidants with electrogenerated hexacyanoferrate(III) ions and their use in vegetable oils analysis

Stoichiometric coefficients in reactions of sterically hindered phenols and α-tocopherol with electrogenerated hexacyanoferrate(III) ions have been found. Schemes of oxidation reactions via hydroxyl groups in the molecular structure have been proposed. The relative standard deviation of the results of determination of the indicated compounds in model solutions is ≤5%. It has been shown that α-tocopherol and ionol are quantitatively extracted from vegetable oil by 15-min single extraction at the oil-to-acetonitrile ratio 1: 2.5. A procedure for the extraction-coulometric determination of α-tocopherol in vegetable oil has been developed.     

On the Generation of Intense Cs K X-Rays upon Electron Excitation of a Mo Target Heat Treated in Cs and O2 Vapors

JETP Letters - The possibility of stable generation of intense characteristic Cs radiation upon electronic excitation of a Mo anode target heat treated in Cs and O2 vapors is demonstrated. The...     

Synthesis, Structure, and Membrane Activity of New Glycyrrhetic Acid Derivatives

Derivatives of 3-O-acetyl-18-H-glycyrrhetic acid were synthesized. Their structures and membrane activities were studied.     

Reactions of synthetic phenolic antioxidants with electrogenerated titrants and their analytical applications

Synthetic phenolic compounds (pyrogallol, catechol, hydroquinone, and their derivatives bearing heterocyclic fragments) react with electrogenerated titrants, halogens, and ferricyanide(III) ions. Stoichiometric coefficients of reactions are found. It is shown that the use of ferricyanide(III) ions as a titrant and a one-electron oxidant for the determination of this class of antioxidants offers advantages in comparison with titrants-halogens. The found amounts of pyrogallol, pyrocatechol, and hydroquinone derivatives in model solutions with the RSD 1–5% are fractions of milligrams. It is found that, in the series of the studied synthetic phenolic compounds, pyrocatechol derivatives possess the maximum antioxidant capacity (AOC).     

Electrochemical determination of synthetic antioxidants of bisdithiophosphonic acids

It has been found that bisdithiophosphonic acids with aryl substituents at the phosphorus atom quantitatively interact with electrogenerated halogens under the conditions of galvanostatic coulometry. Stoichiometric coefficients of the reaction between synthetic antioxidants and coulometric titrants-halogens have been determined. The corresponding reaction schemes have been proposed. The total antioxidant capacity (TAC) of the analytes has been estimated by their reaction with electrogenerated bromine. It has been demonstrated that bisdithiophosphonic acids bearing ionolic fragments demonstrate the highest TAC. It has been established that bisdithiophosphonic acids are irreversibly oxidized on a glassy carbon electrode at a potential of 800 mV with 0.1 M NaClO₄ in acetonitrile as the supporting electrolyte. The quantification limit and the analytical range of the analyte determination have been found.     

Influence of pH shift and salting on the energetics of microalgae <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> and <Emphasis Type="Italic">Dunaliella maritima</Emphasis>

The influence of pH shift and NaCl salting on the heat production, oxygen adsorption, and oxygen evolution rates of the unicellular green halotolerant microalga Dunaliella maritima and the freshwater microalga Chlorella vulgaris were investigated. In the growth process of both microalgae the alkalization of their culture medium was observed. And simultaneously it was shown that at increasing NaCl salting of cultural medium its acidification occurs. At alkalization and acidification of Chlorella medium the increase of heat production and respiration rates were observed. At alkalization and acidification of Dunaliella culture the adverse effect of decreasing heat production rate was observed. Acidification of culture medium of both algae led to short-term and sharp increase of photosynthesis measured by polarography and photomicrocalorimeter.