Supercritical Antisolvent Precipitation of Microparticles of Quercetin

Supercritical antisolvent (SAS) process is a recently developed technology to produce micro- and nano particles. This paper presents a continuous apparatus to conduct experiment of SAS process. With the apparatus, the effects of pressure, temperature and flow ratio of CO2 to the solution on the shape and size of particles are studied for the quercetin-ethanol-CO2 system. Spherical quercetin microparticles with diameters ranging form 1 μm to 6μm can be obtained while ethanol is used as organic solvent. The most effective fact on the shape and size of particles is pressure, the next is temperature and the last is the flow ratio of CO2 to solution.

Effect of Process Parameters on Co-precipitation of Paclitaxel and Poly(L-lactic Acid) by Supercritical Antisolvent Process

Paclitaxel(PTX) is an effective anticancer drug with poor solubility in water.Recently,much effort has been devoted into alternative formulations of PTX for improving its aqueous solubility.In this study,PTX and poly(L-lactic acid)(PLLA) were co-precipitated by a supercritical antisolvent(SAS) process using dichloromethane(DCM) and the mixtures of DCM/ethanol(EtOH) or DCM/dimethyl sulfoxide(DMSO) as the solvent,with super-critical carbon dioxide as the antisolvent.The effects of solvent,solvent ratio,temperature,pressure,polymer con-centration and solution flow rate on particle morphology,mass median diameter(Dp50) and PTX loading were in-vestigated using single-factor method.The particle samples were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),laser diffraction particle size analyzer and high pressure liquid chromatogra-phy(HPLC).XRD results indicate that the micronized PTX is dispersed into the PLLA matrix in an amorphous form.SEM indicates that the solvent and the solvent ratio have great effect on the particle morphologies,and particle morphology is good at the volume ratio of DCM/EtOH of 50/50.For the mixed DCM/EtOH solvent,Dp50 increases with the increase of the temperature,pressure,PLLA concentration and solution flow rate,and PTX loading in-creases with pressure.Suitable operating conditions for the experimental system are as follows:DCM/EtOH 50/50(by volume),35 ℃,10-12 MPa,PLLA concentration of 5 g·L-1 and solution flow rate of 0.5 ml·min-1.

Photocatalytic activity of Eu-doped ZnO prepared by supercritical antisolvent precipitation route:When defects become virtues

The aim of this work is to determine the structural and optical properties of Eu-doped ZnO powders prepared by supercritical antisolvent precipitation route(SAS)and to correlate the physico-chemical features with the photocatalytic activity under UV light.Raman and EPR spectroscopy highlight the introduction of novel defects(mainly singly and doubly ionized oxygen vacancies,and oxygen interstitials)on the Eu-doped ZnO samples,which confer higher hydrophilicity to the doped samples with respect to bare ZnO,as evidenced by FT-IR analysis.Additionally,photoluminescence spectra show that the presence of Eu^(3+) totally quenches the visible light emission typical of bare ZnO,which mainly results from the recombination of photogenerated holes at defective sites.The prepared samples were tested both for the photocatalytic degradation of crystal violet dye(CV)and for the partial oxidation of ferulic acid under UV irradiation.The photocatalytic activity results evidence of a higher ability of Eu-doped photocatalysts to degrade CV and ferulic acid,while higher selectivity values towards vanillin are obtained in the presence of bare ZnO.The higher activity of Eu-doped ZnO photocatalysts is linked to the stabilization of photogenerated holes and to their higher hydrophilicity,both brought by the generation of defective sites induced by the presence of Eu^(3+) ions within the ZnO lattice.

Nanoencapsulation of Lutein with Hydroxypropylmethyl Cellulose Phthalate by Supercritical Anfisolvent

Lutein was nano-encapsuled with hydroxypropylmethyl cellulose phthalate （HPMCP） to maintain its bioactivity and to avoid thermal/light degradation. Supercritical antisolvent precipitation was applied to prepare lutein/HPMCP nano-capsule. The effects of several operating parameters on the yield, lutein loading, encapsulation efficiency, particle size and particle size distribution of the nanocapsule were investigated. The mean diameter of nanocapsules ranged from 163 nm to 219 nm under appropriate experimental conditions. The result of scanning electron microscope showed that the nanocapsules were nearly spherical. The highest yield reached 95.35% when the initial concentration of lutein was saturated. The highest lutein loading of 15.80% and encapsulation efficiency of 88,41% were obtained under the conditions of 11 MPa, 40℃ and CHPMCP： Clutein= 5：1. The results may promote the application of lutein in food industry.

Study of the Liquid Phase Volume Expansion for CO_2/Organic Solvent Systems

The supercritical antisolvent （SAS） process has been developed in recent years for the tormation of nanoand micro-particles. It is necessary to study the liquid phase volume expansion （LPVE） and find the relationships between the operating conditions and the LPVE in order to develop a practical method for determining the operation conditions and selecting an organic solvent for SAS process. The PR equation of state with vdW-1 mixing rule is used to calculate the LPVE for CO2/toluene, CO2/acetone and CO2/ethyl acetate systems, and the results show that the LPVE for each CO2/organic solvent system decreases as the temperature increases. The relationship between the LPVE and the solubility of CO2 in the liquid phase for CO2/organic solvent systems is investigated, and the results show that the LPVE is determined directly by the solubility of CO2 in the liquid phase, xCO2, and can be related to xCO2 independently. No matter what system of CO2/organic solvent is and how different the temperature is, the LPVEs have little difference as long as the solubility of CO2 in the liquid phase, xCO2, keeps constant. The lower temperature is always favorable to the SAS process. The higher the solubility of CO2 in an organic solvent under certain operation condition, the more suitable it is to the SAS process.