Volume 74, Nº 2 (2019)

We analyze and systematize publications in the field of digital colorimetry over the past 15 years. Different versions and possibilities of the method are considered; the fields of its application and the prospects for use in chemical analysis are noted. Colorimetric units based on household optical gadgets (smartphones, office flatbed scanners, etc.) that enable the obtaining of raster images are described.

The mechanism of the C=C bond’s migration in allyl phenyl sulfide in the presence of methanesulfonic acid is analyzed by quantum chemistry using the density functional theory in the B3PW91/6-31G** approximation. The reaction proceeds through the formation of 1-(phenylthio)prop-2-ylium and 2-methyl-1-phenylthiiranium. The calculations show the possibility of the protonation of allyl phenyl sulfide and deprotonation of the resulting cation to phenyl propenyl sulfide. The possibility of the opening of the thiiranium cation under the action of methyl sulfonate to form a complex of phenyl propenyl sulfide with methanesulfonic acid is also shown. Comparison of the results of calculations with and without a solvent shows that the energy profile of the reaction (ΔG₂₉₈⁰, and ΔE_tot^ZPE) is practically preserved.

Methods for the synthesis of copper nanoparticles in a micellar solution of an anionic surfactant, sodium dodecyl sulfate, are improved by optimizing the molar ratios of the precursor and the reductant, Cu(II): N₂H₄ of 1 : 4, 1 : 8, 1 : 20, 1 : 40, 1 : 100, and 1 : 150 at a pH of 11.1 and pH values of the reaction medium of 10.9, 11.0, 11.2, and 11.9 at the optimum Cu(II): N₂H₄ molar ratio of 1 : 150. The effect of increasing the Cu(II) : N₂H₄ molar ratio on the growth in the absorbance of suspensions of copper nanoparticles is established. The stability of solutions over time is studied using the spectrophotometric analysis of colloidal dispersions of copper nanoparticles obtained at a Cu(II) : N₂H₄ molar ratio of 1 : 150 and values of pH of 10.9, 11.0, 11.2, and 11.9. The process of the aggregation of copper particles accompanied by a hypsochromic shift of the absorption band of surface plasmon resonance towards larger wavelengths is studied by dynamic light scattering. Scanning electron microscopy has shown that copper particles obtained at a Cu(II) : N₂H₄ molar ratio of 1 : 150 and pH values of 10.9, 11.0, and 11.2 have a spherical shape with dimensions in the range from 12 to 176 nm.

The solubility of ketoprofen (nonsteroidal anti-inflammatory drug) from solid dispersions based on polyvinylpyrrolidone (PVP-10000, PVP-12600 and PVP-24000) is studied. The use of solid dispersions (SDs) increases the solubility and dissolution rate. The solubility of ketoprofen from SD increases by 1.5–2.6 times. The rate of dissolution from SDs increases by 1.5–3.2 times. The studies conducted by a complex of physical and chemical methods suggest that an improved release of ketoprofen from SDs is due to the generation of solid solution of the active substance in the polymer, the formation of intermolecular hydrogen bonds of the active substance with polyvinylpyrrolidone and the solubilizing effect of the polymer during the dissolution of ketoprofen. The results obtained can be used in the development of fast-dissolving solid dosage forms of ketoprofen with enhanced bioavailability.