Study of factors affecting the in vitro release of diclofenac sodium from hypromelose-based gels

The aim of our study was to identify factors affecting the in vitro release of diclofenac sodium (DS) from hypromellose-based gels (HPMC). Materials and methods. Gels with HPMC and liquids without HPMC were studied by viscosity-rotating viscometer method and spin probe electron paramagnetic resonance spectroscopy. Rheograms were used to determine the flow behavior and the apparent viscosity, and the EPR spectra were used to determine the rotational correlation time (τ–1) of the dissolved spin probes. The in vitro release tests were performed using vertical diffusion cells according to a validated procedure. The assay of DS and isopropyl alcohol (IPA) in the receptor medium was performed by high performance liquid chromatography (HPLC) and gas chromatography (GC) according to validated procedures, and the water content was determined using semi-micro method. Results. The apparent viscosity of the gels increased with increasing HPMC content and depended on the HPMC grade. The high apparent viscosity of the gels did not affect the values of τ–1 of the dissolved spin probes. In viscous gels and Newtonian fluids, the composition of which corresponded to the dispersion medium of gels, the values of τ–1 were identical and were in the range of rapid rotation, which is a prerequisite for similar and rapid release of the dissolved substances from gels and liquids. It was shown that the HPMC-based gel and Newtonian liquid without HPMC in terms of in vitro release parameters DS and IPA were equivalent. During in vitro testing the release of dissolved DS increased with increasing its concentration in the gel and depended on the dispersed state of DS. When the content of IPA was changed from 45.0 % to 22.5 %, the water absorption by the gel and the release of IPA decreased, and the release of DS increased, which was due to the decrease in the solubility of DS in the gel. Conclusions. HPMC, which provided high apparent viscosity of the gels, did not affect the value of τ–1 of the dissolved spin probes and the in vitro release of DS from the gels. The gel and Newtonian liquid were equivalent in terms of in vitro release of DS and IPA. The release of DS altered proportionally with the concentration of DS and depended on its dispersed state. As the content of IPA decreased, the release of IPA decreased, but the release of DS increased because of the decrease in the solubility of the DS in the gel

THE LID-DRIVEN HYDROMAGNETIC FLOW OF NEWTONIAN AND NON-NEWTONIAN LIQUIDS IN A SQUARE CAVITY

In this paper, we formulate the steady hydromagnetic lid-driven cavity problem in a stream function-vorticity form for weakly electrically conducting Newtonian and non-Newtonian liquids. Then we solve them by using the concept of pseudo time derivative. The classical benchmark results of the Newtonian liquid are recovered as a limiting case and the inhibiting influence of the magnetic field on the Newtonian and non-Newtonian liquids’ flow field is clearly depicted through graphs. We also show certain aspects of the flow for the first time in tables.

Heat and Mass Transfer Analysis in Chemically Reacting Flow of Non-Newtonian Liquid with Local Thermal Non-Equilibrium Conditions: A Comparative Study

In the current paper, we endeavour to execute a numerical analysis in connection with the boundary layer flow induced in a non-Newtonian liquid by a stretching sheet with heat and mass transfer. The effects of chemical reactions and local thermal non-equilibrium (LTNE) conditions are considered in the modelling. The LTNE model is based on energy equations, and provides unique heat transfer for both liquid phases. As a result, different temperature profiles for both the fluid and solid phases are used in this work. The model equation system is reduced by means of appropriate similarity transformations, which are then numerically solved by employing the classical Runge–Kutta (RK) scheme along with the shooting method. The resultant findings are graphed to show the effects of various physical factors on the involved distributions. Outcomes reveal that Jeffrey fluid shows improved velocity for lower values of porosity when compared to Oldroyd-B fluid. However, for higher values of porosity, the velocity of the Jeffery fluid declines faster than that of the Oldroyd-B fluid. Jeffery liquid shows improved fluid phase mass transfer, and decays more slowly than Oldroyd-B liquid for higher values of chemical reaction rate parameter.

Hydrodynamics of Turbulent Bed Contactor with Non Newtonian Liquids

Little information is available in literature in terms of the hydrodynamic characteristics in a turbulent bed contractor [sic] (TBC) with viscous liquids. In this study, the hydrodynamic characteristics in three-phase turbulent bed contactor with counter current flow of air and non-Newtonian liquid was studied and compared with that of Newtonian liquid under consistent conditions. Aqueous solutions of carboxy methyl cellulose (CMC) with apparent viscosities ranged between 5 to 25 cP were used as non-Newtonian liquid. The hydrodynamic parameters iinvestigatedwere: bed pressure drop, minimum fluidization velocity, liquid holdup, bed expansion, and gas holdup. The effect of rheological properties of the CMC aqueous solutions and operating parameters on hydrodynamic characteristics of the TBC were examined. Results showed that increasing CMC concentration increased the net pressure drop across the bed and the liquid holdup, while the gas holdup and bed expansion decreased. At that quoted apparent viscosity range, aqueous solutions of CMC behaved as Newtonian viscous liquids in the TBC.

Hydrodynamics of Turbulent Bed Contactor with Non Newtonian Liquids

Little information is available in literature in terms of the hydrodynamic characteristics in a turbulent bed contractor [sic] (TBC) with viscous liquids. In this study, the hydrodynamic characteristics in three-phase turbulent bed contactor with counter current flow of air and non-Newtonian liquid was studied and compared with that of Newtonian liquid under consistent conditions. Aqueous solutions of carboxy methyl cellulose (CMC) with apparent viscosities ranged between 5 to 25 cP were used as non-Newtonian liquid. The hydrodynamic parameters iinvestigatedwere: bed pressure drop, minimum fluidization velocity, liquid holdup, bed expansion, and gas holdup. The effect of rheological properties of the CMC aqueous solutions and operating parameters on hydrodynamic characteristics of the TBC were examined. Results showed that increasing CMC concentration increased the net pressure drop across the bed and the liquid holdup, while the gas holdup and bed expansion decreased. At that quoted apparent viscosity range, aqueous solutions of CMC behaved as Newtonian viscous liquids in the TBC.