Search results for "Chemical engineering"

CFD Simulation of Particle Distribution in Stirred Vessels

2000

In this work the particle concentration distribution in two-phase stirred tanks is simulated on the basis of information on the three-dimensional flow field, as obtained by numerical solution of the flow equations (CFD) using the well known k –ɛ « turbulence model. Two modelling approaches are attempted. In the simpler method the flow field is first simulated neglecting the influence of the solid phase; on the basis of the resulting flow field a very simple sedimentation model is employed for solving the solids mass balance equations in order to compute the particle concentration field. In this case no inertial effects on the solid particles are considered, so that the convective and diffus…

Particle drag coefficients in turbulent fluids

1998

Abstract An accurate estimation of particle settling velocities, and/or of particle drag coefficients, is required for modelling purposes in many industrially important multiphase processes involving the suspension of millimetre and sub-millimetre size particles in a liquid phase. It is known that the settling velocity of particles in a turbulent fluid may be significantly different from that in the still fluid, depending on turbulence and particle characteristics. Despite the wide range of processes that would benefit from a thorough understanding of this phenomenon, experimental data and reliable correlations are still lacking in the scientific literature, especially for the case of the a…

Analysis of hazardous chemicals by “stand alone” drift tube ion mobility spectrometry: a review

2020

Ion mobility spectrometry (IMS) is a widely used technique based on gas phase ion separation under an electric field by differences in ion mobilities. In the last decade, IMS techniques have received increased attention due to their high operational speed and sensitivity. Currently, there are different IMS devices focused on solving different analytical performances, mainly based on linear drift tube (DT IMS), traveling wave, and field asymmetric waveform ion mobility spectrometers. In this review we summarize the main applications of DT-IMS devices for the determination of semi-volatile hazardous chemicals such as: illegal drugs, pesticides, explosives, chemical warfare agents, and others,…

New binary solid dispersion of indomethacin with surfactant polymer: From physical characterization to in vitro dissolution enhancement

2009

This article investigated preparation of solid dispersions containing a poor water-soluble drug, indomethacin (IND), and a new surfactant polymer, polyoxyethylene 32 distearate (POED). Solid dispersions were prepared by the melting method and characterized by DSC, hot-stage microscopy (HSM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). DSC and HSM analyses performed on IND/POED physical mixtures indicated that IND could dissolve in liquid POED. The materials showed complete miscibility at liquid state. Combination of DSC, XRD, and SEM revealed that these materials had limited miscibility at the solid state. Up to 20% w/w IND in POED, we did not detect significant modifica…

Predictability of drug encapsulation and release from propylene carbonate/PLGA microparticles.

2020

Abstract Key parameters for microparticle-based parenteral depot formulation development are entrapment efficiency and sustained drug release, which both depend on the intermolecular affinity of the components. Here, partial solubility parameters were evaluated as descriptors for 21 drug substances and 3 polymers in propylene carbonate (PC). Out of these 21 drug substances, eight BCS class II substances (celecoxib, clotrimazole, erythromycin, ibuprofen, indomethacin, itraconazole, lopinavir and ritonavir) were encapsulated using PLGA (Poly(DL-lactide-co-glycolide)) as polymer matrix and PC as a polar aprotic solvent in order to assign microparticle properties to potential affinity-related i…

Microparticle preparation by a propylene carbonate emulsification-extraction method

2018

Abstract The use of various harmful organic solvents for microparticle formulations is still widespread. Here, an alternative low toxicity solvent (propylene carbonate; PC) is proposed for the preparation of poly(lactic-co-glycolic-acid) (PLGA) microparticles. Based on the classical emulsification-solvent extraction methodology, the use of PC offers the unique advantage of an additional solvent extraction step using hydrolytic solvent cleavage during microparticle preparation. Spherical, rough-surfaced microparticles were obtained with a volume median diameter range from 20 to 60 µm. The residual PC content has been identified to be the major factor for the solidification hindrance, leading…

3D-Printed Solid Dispersion Drug Products.

2019

With the well-known advantages of additive manufacturing methods such as three-dimensional (3D) printing in drug delivery, it is disappointing that only one product has been successful in achieving regulatory approval in the past few years. Further research and development is required in this area to introduce more 3D printed products into the market. Our study investigates the potential of fixed dose combination solid dispersion drug products generated via 3D printing. Two model drugs&mdash

Modified Montmorillonite as Drug Delivery Agent for Enhancing Antibiotic Therapy

2021

The appealing properties of surfactant-intercalated Montmorillonites (Organo-montmorillonite, OMt) were successfully investigated to propose an effective drug delivery system for metronidazole (MNE) antibiotic therapy. This represents a serious pharmaceutical concern due to the adverse drug reactions and the low targeting ability of MNE. The non-ionic surfactant Tween 20 was used to functionalize montmorillonite, thus accomplishing the two-fold objective of enhancing the stability of clay dispersion and better controlling drug uptake and release. The adsorption process was performed under different experimental conditions and investigated by constructing the adsorption isotherms through hig…

Cytotoxicity of aloe-emodin towards several drug sensitive cells and their resistant counterparts

2017

Montmorillonite nanodevices for the colon metronidazole delivery.

2013

The adsorption profiles of the antibiotic metronidazole (MNE) into the K10-montmorillonite (MMT-K10) clay and the subsequent release have been investigated as a function of pH and MNE/MMT-K10 ratio, in order to evaluate the potential of the MNE/MMT-K10 hybrids as controlled drug delivery system. The adsorption mechanism has been first elucidated by performing complementary equilibrium and kinetic studies and through the X-ray diffractometry (XRD) characterization of the obtained composite materials. The gathered results allowed us to propose a mechanism consisting of a multi-step pathway involving the neutral and the cationic form of the drug, which interact with different sites of the clay…