Reactions of superoxide anion radical with antioxidants and their use in voltammetry

Kinetic parameters were calculated for the electrochemical reduction of oxygen at a glassy-carbon electrode with the generation of superoxide radical anions in a 0.05 M solution of (C2 H5 )4NI in dimethylformamide in the presence of fat-soluble antioxidants, retinol and α-tocopherol. A procedure based on the protonation of the radical anion with antioxidant molecules is proposed for the voltammetric determination of antioxidants to determine milligram amounts of retinol and α-tocopherol in model solutions (RSD = 1-2%). The calibration graphs for retinol and α-tocopherol are linear in the concentration ranges 9.7 × 10 -5-2.3 × 10-3 and 6.2 × 10-4-3.1 × 10-3 M, respectively. The detection limits for retinol and α-tocopherol are 4.8 × 10-5 and 4.1 × 10 -4 M, respectively. The procedure was applied to the determination of the active component (retinol and α-tocopherol) in pharmaceuticals. © 2005 Pleiades Publishing, Inc

Determination of some liposoluble antioxidants by coulometry and voltammetry

It is found that the interaction of retinol, ergocalciferol, and cholecalciferol with electrochemically generated bromine proceeds rapidly and quantitatively. The stoichiometric coefficients of the reaction are 1:2, 1:7, and 1:3, respectively. A coulometric determination of microgram amounts of individual liposoluble antioxidants in model solutions was performed with RSD = 1-5%. The voltammetric response of retinol and α-tocopherol was studied at a stationary platinum microelectrode in 0.1 M HClO 4 and 0.1 M CH 3COONa in acetonitrile. The quantification limit for α-tocopherol is 2.7 × 10 -4 M in 0.1 M HClO 4, and the quantification limits for retinol are 4.1 × 10 -5 M in 0.1 M HClO 4 and 2.1 × 10 -5 M in 0.1 M CH 3COONa. A procedure for the coulometric determination of total free liposoluble antioxidants in human blood serum is proposed

Preconcentration of Simazine from aqueous solutions with an immunosorbent and its quantitative determination

The optimal conditions were found for sorption preconcentration of Simazine (herbicide of sym-1,3,5-triazine group) from aqueous solution with immobilized antibodies. The main characteristics of immobilized antibodies as sorbents for Simazine were determined. © 2005 Pleiades Publishing, Inc

New indicator reactions involving sulfur-containing organic compounds for the kinetic determination of selenium

New indicator reactions were proposed for the determination of selenium by the kinetic method based on the reduction of Methylene Blue by some sulfur-containing organic compounds. It was demonstrated that a high sensitivity of the determination of selenium is attained using unithiol and thiomalic, 2,3-dithiomercaptopropionic, and rubeanic acids as reducing agents. In the presence of unithiol, down to 4 ng/mL selenium can be determined. © 2001 MAIK "Nauka/Interperiodica"

An amperometric monoamine oxidase biosensor for determining some antidepressants

An amperometric biosensor based on a platinum screen-printed electrode and immobilized monoamine oxidase is developed to determine antidepressants of different classes. Petylyl, pyrazidol, and flu-oxetine can be determined with determination limits of 8 × 10-9, 8 × 10-7, and 8 × 10-10 M, respectively. A procedure is proposed for determining fluoxetine in tablets. It is shown that petylyl can be selectively determined by an immunochemical technique using the developed biosensor and immobilized antibodies in the concentration range from 1 × 10-4 to 1 × 10-8 M. © 2007 MAIK Nauka

Reaction of 2,3-dimethylmercaptopropionic acid with methylene blue as an indicator reaction for the kinetic determination of selenium

A new indicator reaction between 2,3-dimethylmercaptopropionic acid and Methyl Blue was proposed for the kinetic determination of selenium. The optimal reaction conditions were found. A linear relationship was observed between the induction period and the Se(IV) concentration in the range between 0.9 and 9.6 ng/mL Se. Masking with EDTA and solvent extraction with diethyldithiophosphoric acid can be used for the separation of interfering elements forming complexes with the reagent. © 2001 MAIK "Nauka/Interperiodica"

Estimation of several antidepressants using an amperometric biosensor based on immobilized monoamine oxidase

An amperometric biosensor was developed on the basis of a printed platinum electrode and immobilized monoamine oxidase for detecting antidepressants of various classes. The analytical potential of the electrode was assessed: Petylyl (desipramine) and pyrazidol could be estimated from lower detection limits of 8 × 109 M for Petylyl and 8 × 107 M for pyrazidol. A method for estimating pyrazidol in tablets is described. © 2007 Springer Science+Business Media, Inc

Capabilities of amperometric monoamine oxidase biosensors based on screen-printed graphite electrodes modified with multiwall carbon nanotubes in the determination of some antidepressants

© 2015, Pleiades Publishing, Ltd. Amperometric biosensors based on planar screen-printed graphite electrodes modified with multiwall carbon nanotubes (MWCNTs) and immobilized monoamine oxidase enzyme (MAO) have been proposed for the determination of antidepressants (imipramine, afobazole, and phenazepam). The operation of the proposed biosensors is based on the inhibiting ability of antidepressants. The analytical capabilities of the proposed devices have been compared to those of biosensors based on the electrodes unmodified with MWCNTs. The proposed biosensors can be used for the control of both residual amounts of drug substances in biological fluids (urine) and the active ingredient in dosage forms

Carbon nanotube-modified electrodes for electrochemical DNA-sensors

Glassy-carbon electrodes (GCEs) are modified with preoxidized multiwalled carbon nanotubes (CNTs). According to the data of atomic force microscopy, the layers of CNTs on GCEs possess a homogeneous nanostructurized surface. The voltammetric properties of a GCE/CNT depend on the modifier load. Guanine and deoxyguanosine monophosphate are strongly adsorbed on GCE/CNT and oxidized at +690 and +930 mV (pH 7.0), respectively. The oxidation current of guanine DNA nucleotides adsorbed on a GCE/CNT is significantly higher for the thermally denaturated biopolymer than for the native one. Our results are of interest for the development of sensors based on the electrochemical properties of nucleic acids. © Nauka/Interperiodica 2007