Preparation and characterization of dipicolinatovanadium(V) complexes. Kinetics and mechanism of their reaction with hydrogen peroxide in acidic media

Silver nanoplates (SNPs) having different size were synthesized by a seed-mediated method. The seeds -silver nanoparticles with 4 – 6 nm diameters were synthesized first by reducing silver nitrate with sodium borohydride in the present of Trisodium Citrate and Hydrogen peroxide. Then these seeds were developed by continue reducing Ag\(^+\) ions with various amount of L-Ascorbic acid to form SNPs. Our analysis showed that the concentratrion of L-Ascorbic acid, a secondary reducing agent, played an important role to form SNPs. In addition, the size and in-plane dipole plasmon resonance wavelenght of silver nanoplates were increased when the concentration of added silver nitrate increased. The characterization of SNPs were studied by UV-Vis, FE-SEM, EDS and TEM methods.

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A Simple, Green and Fast Ultraviolet Spectrophotometric Method for the Carbamide Peroxide Determination in Dental Whitening Products

Current Pharmaceutical Analysis ◽

10.2174/1573412913666171027164015 ◽

2019 ◽

Vol 15 (2) ◽

pp. 138-144

Author(s):

Fabiana Vieira Lima ◽

Aline Farias ◽

Cassiana Mendes ◽

Simone Gonçalves Cardoso ◽

Marcos Antônio Segatto Silva

Keyword(s):

Hydrogen Peroxide ◽

Pharmaceutical Products ◽

Reference Solution ◽

Iodometric Titration ◽

Carbamide Peroxide ◽

Ultraviolet Detection ◽

Water As Solvent ◽

Development And Validation ◽

Dental Whitening

Background: The carbamide peroxide is the most commonly active ingredient used for home dental whitening products, its quantification in pharmaceutical products is of extreme importance due to the relation with the products potency and the previously related low carbamide peroxide stability. Once, there is only one official carbamide peroxide determination based on iodometric titration, this method is time-consuming and generates a lot of residues. The aim of this study was to carry out development and validation of a simple and fast ultraviolet spectrophotometer assay to quantify an innovative dental whitening gel. Methods: The proposed method was validated according international conference on harmonization guideline. Procedure is based on the iodide/iodine redox chemistry; iodine released through the action of hydrogen peroxide of carbamide peroxide with ultraviolet detection at 350 nm. Results: The procedure was linear in the concentration range of 1.0-4.0 µg/mL, specific to the excipients, robust for the evaluated parameters (variation of wavelength (± 5 nm); reagent addition (± 10%)), showing the results of RSD 1.88 and 0.39% respectively. Repeatability precision was RSD = 1.42%, with accurate RSD = 2.15% by adding reference solution. The assay used only water as solvent for sample preparation. In comparison to the pharmacopeial method, the latter is more time-consuming, as it generates a lot of residues, and it could not quantify small CP dosages. Conclusion: Thus, the proposed method was proved to be suitable to determine carbamide peroxide during the development and characterization of nanoparticle formulations in the present study.

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Mn-Mo-O Catalysts for Methanol Oxidation. I. Preparation and Characterization of the Catalysts

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19922529 ◽

1992 ◽

Vol 57 (12) ◽

pp. 2529-2538 ◽

Cited By ~ 3

Author(s):

Krasimir Ivanov ◽

Penka Litcheva ◽

Dimitar Klissurski

Keyword(s):

Methanol Oxidation ◽

Solution Concentration ◽

Alkaline Media ◽

Acidic Media ◽

Chemical Methods ◽

X Ray ◽

Ph Values ◽

Precipitate Composition

Mn-Mo-O catalysts with a different Mo/Mn ratio have been prepared by precipitation. The precipitate composition as a function of solution concentration and pH was studied by X-ray, IR, thermal and chemical methods. Formation of manganese molybdates with MnMoO4.1.5H2O, Mn3Mo3O12.2.5H2O, and Mn3Mo4O15.4H2O composition has been supposed. It is concluded that pure MnMoO4 may be obtained in both acid and alkaline media, the pH values depending on the concentration of the initial solutions. The maximum Mo/Mn ratio in the precipitates is 1.33. The formation of pure Mn3Mo4O15.4H2O is possible in weakly acidic media. This process is favoured by increasing the concentration of initial solutions.

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