Application of gold nanoparticles in the methods of optical molecular absorption spectroscopy: main effecting factors

Results of studies on the analytical capabilities of gold nanoparticles in the methods of optical molecular absorption spectroscopy are reported. Peculiar effects of the nature of nanoparticle stabilizer, its charge, morphology of nanoparticles, form in which they are present in the system (in a colloidal solution or as a part of a nanocomposite with polyurethane foam) upon the determination of organic compounds (thiols, cationic compounds, catecholamines) and inorganic anions are considered. The determination is based on aggregation of nanoparticles or change in the state of their surface and morphology as a result of silver coating, leading to significant spectral and color changes, which can be monitored both by optical molecular absorption spectroscopy and visually. The ways to increase sensitivity and to control selectivity of the analysis using gold nanoparticles and their nanocomposites are outlined.

Evaluation of the Release of Ascorbic Acid in Prolonged-Release Tablets by in vitro Dissolution Tests

In vitro dissolution tests are an extremely important tool in the development and quality control of drugs, making it possible to evaluate the performance or efficiency of the pharmaceutical form in releasing the active substance through the amount dissolved in the dissolution medium when the product is subjected to specific equipment. In this sense, the main objective of the present study was to evaluate the release of ascorbic acid in prolonged release commercial vitamin C tablets by dissolution tests. Ascorbic acid and drugs of two different brands were characterized using the techniques of Molecular Absorption Spectroscopy in the Region of Infrared (IR), Thermogravimetry/Derived Thermogravimetry (TG/DTG) and Differential Scanning Calorimetry (DSC). The in vitro dissolution tests were performed in a dissolver with a paddle apparatus at a temperature of 37°C (± 0.5°C), employing 900 mL of ultrapure water as the dissolution medium and a stirring speed of 50 rpm. The ascorbic acid dissolved in the aliquots of dissolution media obtained during the tests were quantified using the UV-Vis Molecular Absorption Spectroscopy technique. From the dissolution profiles, it was observed that the formulations of both brands promoted a prolonged release of ascorbic acid. The brand drug A dissolved about 67% of the active principle in about 360 minutes. The brand drug B, however, dissolved about 72% at the same dissolution time. Release kinetics was evaluated using kinetic models such as order zero, first order and Higuchi. The model that best fit the experimental data was that of Higuchi.

STUDY OF STRUCTURAL AND FUNCTIONAL COMPOSITION OF SOIL HUMUS ACIDS OF EURO-ARCTIC REGION BY MOLECULAR ABSORPTION SPECTROSCOPY (UV / VISIBLE)

Results of the structural and functional composition of soil humus acids in the Euro-Arctic Region are presented. The molecular absorption spectroscopy (UV / visible) was used to evaluate eco-protective role of soils in relation to heavy metals, which is especially important for the sensitive soils of the Arctic, formed under the influence of cryogenic processes. Different types of soils of the Euro-Arctic region: gleyish easy loamy pelosi on loamy moraine (Kanin Peninsula, Cape Kanin Nos); humus peat oligotrophic soil (Kolguev Island, Bugrino village); typical non-calcic loamy gley soil (Vaigach Island); gray humous iron sandy lithozem (Archipelago Franz Josef Land, Heys Island) were analyzed. An alkaline solution of sodium pyrophosphate was used to extract humus acids for investigate of the structural and functional composition. Humic, fulvic and gimatomelanic acids were extracted from a humus by conforming solvents with additional fulvic acids extraction by adsorption chromatography using activated carbon as a sorbent. UV mini-1240 spectrophotometer (Shimadzu) was used to record the UV / visible spectra using 0.005% alkaline solutions (0.1 N NaOH) of humus acids. It was demonstrated that humic and gimatomelanoic acids of humus peat oligotrophic soil have more developed peripheral aliphatic component. These acids have more ability to bind heavy metals and show their eco-protective role. The humus acids of other types of soils region have a more developed aromatic component in the Euro-Arctic. Such parameters as: calculated by the Pieravuori formula aromaticity, extinction coefficient Е0.005%1cm,465, adsorption ratio D400 /D600, characterizing the degree of humification and the adsorption ratio D465 / D650, characterizing the degree of aromatic nucleus condensation and conjugate fragments were used in the quantitative assessment of the nature of humus acids. Quantitative analysis of UV/visible spectra confirmed that the maximum barrier mechanism with respect to heavy metals will be the humic and gimatomelanoic acids of humus-peat oligotrophic soil, due to the high content of phenolic and carboxyl groups in these molecules, oxidation and a more developed chain of conjugated bonds in them in comparison with other acids. However, it was found that in all types of soils studied the process of humus formation proceeds mainly by a degradation type, that is, in the direction of formation of fulvic acids. Forcitation:Prilutskaya N.S., Korel'skaya T.A., Popova L.F. Study of structural and functional composition of soil humus acids of euro-arctic region by molecular absorption spectroscopy (UV / visible). Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 97-103