1,721,143 research outputs found
Supercritical Fluid Adsorption of Domperidone on Silica Aerogel
Full text linkSilica aerogel (SA) was loaded with domperidone to demonstrate the potentiality of adsorption processes based on the usage of supercritical carbon dioxide to treat poorly water-soluble drugs, forming new kinds of drug delivery systems. The effects of pressure, temperature and solution concentration on loaded SA were studied. Adsorption isotherms were measured at 35°C and 45°C and fitted with Langmuir model. Release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. Results showed that domperidone can be uniformly dispersed into the aerogel and that the release rate of domperidone from the composite, constituted by drug and silica aerogel, is much faster than that of the crystalline drug. The proposed adsorption method is suitable for the production of domperidone fast release tablets
Use of urea as habit modifier in supercritical antisolvent micronization of sulfathiazole
No full textThe purpose of this work is to study the effect of urea as an additive for the habit modification of sulfathiazole
(STZ) crystals formed using supercritical antisolvent (SAS) precipitation. The process was performed using
acetone and carbon dioxide as solvent and antisolvent, respectively. The effect of STZ concentration, urea
concentration, temperature, and pressure on the crystals habit was investigated, and the obtained products
were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning
calorimetry (DSC). Urea was found to be very effective in the modification of the crystal habit and size of
STZ crystals. The habit changed from a plate shape to spherical particles with a very narrow particle size
distribution at a urea/STZ mass ratio of 1%. Mean particle size ranged between 0.5 and 1 ím depending on
the STZ concentration in acetone. XRD and DSC analysis indicated the formation of a form I polymorph
among the five known polymorphisms of STZ. Because of rapid precipitation, only partly crystalline particles
were observed with respect to the raw material. Despite the use of urea as an additive, no detectable urea
residue was found in the crystals, because urea is soluble in carbon dioxide and is effectively removed during
the washing step with CO2. It is, thus, concluded that urea is mainly adsorbed on the crystal surface rather
than being incorporated into the lattice of the STZ crystals
Fixed Bed Adsorption of Drugs on Silica Aerogel from Supercritical Carbon Dioxide Solutions
Full text linkSupercritical adsorption coupled with the high adsorption capacity of silica aerogel allows the preparation of a new kind of delivery systems of poor water soluble drugs. In order to overcome drawbacks of conventional techniques where the use of liquid solvents can cause the fracture of aerogel porous structure, in this work a new adsorption process of drugs from a supercritical mixture is proposed. Adsorption takes place from a fluid solution of the drug in supercritical CO2 and ethanol as cosolvent. A fixed bed adsorption plant has been developed to allow fast mixing of fluid phase and effective contact in the adsorption column. The use of ethanol as cosolvent allows to overcome the limitation of supercritical adsorption due to low solubility of many drugs in supercritical CO2. Adsorption isotherms were measured for one-model substance, nimesulide, at 40°C, and breakthrough curve was experimentally obtained. The drug loading of the drug into silica aerogel was up to 9 wt%. The drug composite was characterized using scanning electron microscopy, and release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. The dissolution of nimesulide from loaded aerogel is much faster than dissolution of crystalline nimesulide. Around 80% of nimesulide dissolves from the aerogel within 6 minutes, whereas dissolving 80% of the crystalline drug takes about 90 min
Supercritical Fractionation of Fried Oil in a Packed Tower at Different Pressure using CO2 and Hexane as Cosolvent
No full textFractionation of fried oils by Supercritical Carbon Dioxide (SC-CO2) is one of the
most interesting purification techniques, since a selective separation of the oil components can
be attained [1, 2, 3]. Unfortunately, the specific quantity of CO2 with respect the feed oil is
fairly high [2, 3] and thus the operating cost is estimated to be high [4]. The hexane as
cosolvent has been successfully used to reduce CO2 flow rate at given pressure [5].
In this work the influence of the hexane concentration at different pressure (P=35 and
28 MPa at T = 323°K) has been tested. At constant CO2 flow rate, 60% vol ratio has been
maintained for hexane in the oil. Ratio between CO2 and oil has been changed from about 53
to about 17.
Fractionation yields and composition of products has been analyzed and discussed.
Experimental results shows that at 323°K hexane cosolvent can allow a significant CO2 flow
rate reduction, still maintaining a good selectivity with respect the oil obtained on tower top.
Moreover, data show that column pressure is the main variable to be considered for oil top
fraction recovery. Hexane cosolvent effect seems to be not significant at 28 MPa, for any CO2
/oil ratio with respect to oil recovery and its composition. The cosolvent feed became more
important for oil recovery and composition at 35 MPa.
Nevertheless, the presence of some percentage of hexane residues in the top fraction of
the oil has been detected and then a further treatment for the oil is necessary
ON THE MODELLING OF FRACTIONATION OF FRIED OIL WITH SUPERCRITICAL CARBON DIOXIDE: A FIRST STEP
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