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.     

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.     

Molar extinction coefficients of some carbohydrates in aqueous solutions

Molar extinction coefficients of some carbohydrates viz. l-arabinose (C₅H₁₀O₅), d-glucose (C₆H₁₂O₆), d-mannose (C₆H₁₂O₆), d-galactose (C₆H₁₂O₆), d(-) fructose (C₆H₁₂O₆) and maltose (C₁₂H₂₄O₁₂) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well.     

Synthesis and Antioxidant Activity of Sterically Hindered Phenol Derivatives of Carboxy- and Sulfobetaines

New multifunctional antioxidants based on carboxy- and sulfobetaines with sterically hindered phenol fragments were synthesized. The antioxidant capacity of the compounds determined in the reactions of their oxidation by electrogenerated bromine is comparable to that of ascorbic acid and ionol.