Interactions of Drug Doxycycline Hyclate with Galactitol in Aqueous Solutions at Different Temperatures by Volumetric and Acoustic Methods

The experimental values of density, ρ and speed of sound, u of doxycycline hyclate drug (0.002–0.014) mol kg−1 in water and (0.1, 0.2 and 0.4) mol kg−1 of aqueous galactitol solutions at temperatures T = (303.15, 308.15 and 313.15) K and at atmospheric pressure have been reported in the present communication. From the experimental values, various derived parameters such as apparent molar volume (ΦV), apparent molar isentropic compression (ΦK), limiting apparent molar volume ($\phi_{\text{v}}^{\text{o}}$), limiting apparent molar isentropic compression ($\phi_{\text{K}}^{\text{o}}$), limiting apparent molar volume of transfer (Δ$\phi_{\text{V}}^{\text{O}}$), limiting apparent molar isentropic compression of transfer (Δ$\phi_{\text{K}}^{\text{O}}$), limiting apparent molar expansibility ($\phi_{\text{E}}^{\text{o}}$), thermal expansion coefficient (α) and acoustic parameters like isentropic compressibility $({{\kappa}_{\text{S}}})$, intermolecular free length (Lf), and specific acoustic impedance (Z) were calculated. The structure-making behaviour of DH in aqueous galactitol solution was determined on the basis of Hepler’s Equation i.e. on the basis of sign of ${\left({\frac{{{{\text{d}}^{2}}\phi_{\text{V}}^{\text{O}}}}{{{\text{d}}{{\text{T}}^{2}}}}}\right)_{\text{P}}}$. The various derived parameters were utilised to interpret the molecular interactions i.e. solute–solute and solute–solvent existing in the studied system.

A Comparative Study of Molecular Interactions of Three Tetracycline Derivatives with Aqueous β-Cyclodextrin Solution at Different Temperatures

A comparative study of complexation behaviour of three tetracycline derivatives viz. doxycycline hydrochloride, oxytetracycline hydrochloride and minocycline hydrochloride with β-cyclodextrin (β-CD) has been done with the help of various thermodynamic and spectroscopic methods. Density (ρ) and conductivity measurements have been carried out for binary drug/water and ternary drug/water/(β-CD) systems at three different temperature viz. 305.15, 310.15 and 315.15 K. The interactions of these tetracycline derivatives with β-cyclodextrin in aqueous solutions are further studied by means of fluorescence spectroscopy and UV-visible spectroscopy. From the measured density (ρ) data, partial molar volume (Φ°ν), partial molar volume expansibility (ϕ°e), Hepler′s constant (∂2ϕ°ν / ∂T2)P and partial molar volume of transfer (Δϕ°ν) have been obtained. From the conductance studies, the energetically favourable interactions are interpreted in the form of free energy change (ΔG) and the apparent association constant (Ka) was estimated from the fluorescence data.

Effect of 1-Octyl-3-Methylimidazolium Salicylate as an Active Pharmaceutical Ingredient (API-IL) on the Thermodynamic Behavior of Aqueous Glycine Solutions at T= 298.15 K

Background: The thermophysical properties of 1-octyl-3-methylimidazolium salicylate as an active pharmaceutical ingredient based on ionic liquid have been investigated in the presence of aqueous solutions of glycine. Therefore, the scope of this article was to determine these properties by measuring the densities, speeds of sound, viscosities, electrical conductances and refractive indices for ternary (glycine + 1-octyl-3-methylimidazolium salicylate + water) soloutions at T = 298.15 K. Methods: A commercial density and speed of sound measurement apparatus was used to measure the density and speed of sound data. Viscosities, electrical conductivities and refractive indices of the studied solutions were measured using digital viscometer, conductivity meter and refractometer, respectively. Results: Variety of properties such as partial molar volume of transfer ∆traV0ϕ, partial molar isentropic compressibility of transfer ∆traK0ϕ, viscosity B-coefficients of transfer ∆traB, ion association constants (KA) and molar refraction RD were determined to investigate the solute-solute and solute-solvent interactions in these systems. Conclusion: The positive values of transfer properties including partial molar volume of transfer (∆traV0ϕ), partial molar isentropic compressibility of transfer (∆traK0ϕ), and viscosity B-coefficients of transfer (∆traB) indicated that in these systems, the ion-polar and polar-polar interactions are dominant. The calculated hydration number showed that dehydration of glycine occurs in presence of this ionic liquid.

The Current Situation at the Argun River Boundary Reach

Water/economic problems and the current changes in the Argun River boundary reach hydrological regime have been analyzed. The Russian-Chinese boundary coincides with the 951 km long reach of the Argun River. In the upper part of this reach there are no tributaries to the Argun so the water regime is completely determined by the runoff from the territory of China. High rate of rise of the neighboring regions of China resulted in the shortage of water resources and a number of environmental problems. Various water/economic measures are taken on the territory of China in order to solve these problems. Diversion of the part of the Khailar River (the Argun River upstream) runoff to the Lake Dalaynor (Khulun) should be specially mentioned. The Lake Dalaynor is sublecte to the water level cyclic changes. The last low-water period started in 1999 and the level lowering was 4.6 m by 2009. The transfer of the part of the Khailar River runoff started in 2009 and over the past period the water level in the lake became 3.5 m higher. The water level rise is observed only in high-water years while during the other periods all the volume of transfer is spent to evaporation. The runoff transfer caused the radical change of the Argun hydrological regime: the lowwater flow demonstrated the 3-5 times decrease, the floodplain flooding recurrence and duration also decreased. The vegetation index (EVI) downstream the transfer canal is an evidence of the floodplain vegetation suppression as a result of water availability decrease. Indices of the Argun River water quality at the starting section of the boundary reach are the worst in the region.

A volumetric and viscometric study of 4-aminobutyric acid in aqueous solutions of metformin hydrochloride at 308.15, 313.15 and 318.15k

Density(?) and viscosity (?) measurements were performed for 4-aminobutyric acid in 0.05, 0.10 and 0.15 M aqueous metformin hydrochloride at 308.15, 313.15 and 318.15 K. The measured values of density and viscosity were used to estimate some important parameters, such as the partial molal volume, V?, the standard partial molal volume V0? , the standard partial molal volume of transfer, ?V0?, the hydration number, nH, the second derivative of the infinite dilution of the standard partial molal volume with temperature ?2V0?/?T2, the viscosity Bcoefficients, variation of B with temperature, dB/dT , the free energy of activation per mole of solvent ??01