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Supercritical Fluids (supercritical + fluid)
Terms modified by Supercritical Fluids Selected AbstractsSupercritical Fluid,Liquid,Solid (SFLS) Synthesis of Si and Ge Nanowires Seeded by Colloidal Metal Nanocrystals,ADVANCED MATERIALS, Issue 5 2003T. Hanrath Abstract Semiconductor nanowires, 5 to 20 nm in diameter and micrometers in length, appear to be promising candidates for a variety of new technologies, including computing, memory, and sensor applications. Suitable for these applications, silicon (Si) and germanium (Ge) nanowires ranging from 4 to 30 nm in diameter and micrometers in length can be produced in high temperature supercritical fluids by thermally degrading organosilane or organogermane precursors in the presence of organic-monolayer-protected gold nanocrystals. Although gas phase vapor,liquid,solid (VLS) methods can be used to produce a variety of different nanowire materials, high temperature supercritical fluids provide wire size control through nanocrystal size selection prior to synthesis, and high product yields due to the high precursor solubility. [source] Extraction and Removal of Caffeine from Green Tea by Ultrasonic-Enhanced Supercritical FluidJOURNAL OF FOOD SCIENCE, Issue 4 2010Wei-Qiang Tang ABSTRACT:, Low-caffeine or caffeine-removed tea and its products are widely welcomed on market in recent years. In the present study, we adopt ultrasonic-enhanced supercritical fluid extraction process to remove caffeine from green tea. An orthogonal experiment (L16 (45)) was applied to optimize the best removal conditions. Extraction pressure, extraction time, power of ultrasound, moisture content, and temperature were the main factors to influence the removal rate of caffeine from green tea. The 5 factors chosen for the present investigation were based on the results of a single-factor test. The optimum removal conditions were determined as follows: extraction pressure of 30 MPa, temperature at 55 °C, time of 4 h, 30% moisture content, and ultrasound power of 100 W. Chromatogram and ultraviolet analysis of raw material and decaffeinates suggests that under optimized conditions, the caffeine of green tea was effectively removed and minished without damaging the structure of active ingredients in green tea. [source] Micronization of the officinal component baicalin by SEDS-PA processCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2007Wen Zhi He Abstract Application of micronizing technologies in processing Chinese herbal medicines is very important to improve the forms of prepared Chinese herbal medicines and promote their therapeutic efficacy. Baicalin, a major active component of the typical Chinese herb medicine Scullateria baicallensis Georgi, was micronized using the Solution Enhanced Dispersion by Supercritical fluids though Prefilming Atomization (SEDS-PA) process with the aim of evaluating the efficiency of applying supercritical fluid precipitation technologies in Chinese herb medicine. This study has shown that acicula or rod-like baicalin crystals with Particle Size (PS) of about 20×100 ,m were successfully micronized by the SEDS-PA process to long rod-like, twisted fiber-like or fibrous net-like microparticles with PS of 0.1-2.2 ,m in width within the range of experiments performed. It was found that a substantial reduction of baicalin microparticles' sizes could lead to a marked increase of adhesions among them and subsequent microparticles agglomeration. With the increase of supercritical CO2 flow rate and the decrease of solution concentration and solution flow rate, smaller and much more agglomerated microparticles were obtained. Increasing pressure led to formation of smaller microparticles. A larger tendency of particles agglomeration was produced at a higher temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Supercritical fluids in medical radioisotope processing and chemistry, Part II: Applications , real and demonstratedJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2003Richard A. Ferrieri Abstract In Part I of this review series, an overview was presented on what the basic properties of supercritical fluids are and how they can, and are being used in many of today's industries as solvents for extraction, chromatography and reaction. A good part of this overview detailed the kinds of equipment needed, and techniques on how to use them for optimal performance. Part II of this series will delve into specific applications of supercritical fluid technology as it relates to aspects of medical isotope processing. The reader will note that very few applications of this technology to Nuclear Medicine have been published. Many potential applications cited within the context of this review derive from preliminary studies carried out in the author's laboratory. These examples are presented to spark interest in future developments of this nature. Copyright © 2003 John Wiley & Sons, Ltd. [source] Application of supercritical fluid extraction to regenerate spent Pd-active carbon catalystENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2007Lidia D Abstract Pd-active carbon-type catalysts are used in a wide variety of processes, typical examples of which are liquid-phase hydrogenation reactions. In the case of these catalysts, a loss of their catalytic activity is observed. The aim of the present work was to assess the possibility of regenerating spent Pd/AC catalysts using supercritical fluid extraction. The following Pd/AC catalyst samples were investigated and compared: a commercial 10 wt % Pd catalyst (Aldrich) (denoted by CC), a spent catalyst (SC), SC subjected to supercritical fluid,CO2 extraction (SC/SFE/C), SC subjected to supercritical fluid,CO2,ethanol extraction (SC/SFE/C-Et), and SC subjected to supercritical fluid,ethane,propane extraction (SC/SFE/E-P). The last three catalysts were additionally subjected to heating in a hydrogen atmosphere at 410 K for 3 h. These were denoted by SC/SFE/C/H, SC/SFE/C-Et/H, and SC/SFE/E-P/H, respectively. The spent Pd/AC catalyst (SC) consists of mixed CC samples used in the reduction with hydrogen of various organic compounds. The catalysts CC, SC/SFE/C, SC/SFE/C/H, SC/SFE/C-Et/H, and SC/SFE/E-P/H were tested in the reduction of octanoylbenzene with hydrogen. The activity of the catalysts was estimated by measuring the reaction time and also the amount of hydrogen used in relation to the theoretical quantity required for the reaction. XPS and XRD methods were used to evaluate the changes occurring in the form of the palladium present on the Pd/AC catalyst surface during the regeneration processes. It was found that supercritical fluid-CO2 extraction followed by heating in a hydrogen atmosphere is the most effective method for regenerating that catalyst. The results of our investigations indicate that regeneration of a spent Pd/AC catalyst, irrespective of the reaction in which it has been used, should be based on the complete removal of byproducts, the purification of the catalyst surface, and the restoration of the original form of the palladium. The procedure proposed in this paper, i.e. SFE (CO2) and heating in H2, fulfils both the conditions mentioned above. © 2007 American Institute of Chemical Engineers Environ Prog, 2007 [source] Dual-Tone Patterned Mesoporous Silicate Films Templated From Chemically Amplified Block CopolymersADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Sivakumar Nagarajan Abstract Directly patterned mesoporous silicate films are prepared using positive- and negative-tone strategies by performing phase selective silica condensation within lithographically exposed poly(styrene- b - tert -butyl acrylate) (PS- b -PtbA) templates containing photoacid generators. The use of supercritical fluid as a process medium enables rapid diffusion of the silicate precursor within the prepatterned block copolymer template film without disrupting its morphology. Template exposure through the mask triggers area selective generation of acid, which in turn both deprotects the poly(tert -butyl acrylate) block to yield a poly(acrylic acid) block and provides a catalyst for silica precursor condensation yielding pattern formation at the device level. Because the acid generated in the UV exposed field preferentially segregates into hydrophilic poly(acrylic acid) domains of the phase segregated, deprotected block copolymer, precursor condensation is simultaneously controlled at nanoscopic length scales via templating by the underlying block copolymer morphology. The ability of PS- b -PtbA to undergo chemical transformation in two stages, deprotection followed by crosslinking, enables precise replications of the photomask in positive and negative tones. Detemplating via calcination yields patterned mesoporous silicate films without etching. Template formulations are optimized using infrared spectroscopic studies and the silicate films are characterized using electron microscopy and scanning force microscopy. [source] SUPERCRITICAL FLUID EXTRACTION AND DETERMINATION OF LUTEIN IN HETEROTROPHICALLY CULTIVATED CHLORELLA PYRENOIDOSAJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2007ZHENGYUN WU ABSTRACT Chlorella is a promising alternative resource of lutein, as it can be cultivated heterotrophically and efficiently in a fermentor. In this study, high density of Chlorella pyrenoidosa was achieved by fed-batch cultivations. Lutein in Chlorella was extracted by supercritical fluid and was determined by high-performance liquid chromatography and liquid chromatography-mass spectrometry. The extraction degree of lutein reached 87.0% after 4-h extraction under the optimized conditions of 50C, 25 MPa and modified CO2 with 50% ethanol. High purity of lutein could be obtained by supercritical fluid extraction with appropriate operation parameters. The whole process developed in this study may be useful for the commercial production of lutein. [source] Crystallization environment of Kazakhstan microdiamond: evidence from nanometric inclusions and mineral associationsJOURNAL OF METAMORPHIC GEOLOGY, Issue 5 2003L. F. Dobrzhinetskaya Abstract Nanometric solid inclusions in diamond incorporated in garnet and zircon from felsic gneiss of the Kokchetav massif, Kazakhstan, have been examined utilizing electron microscopy and focused ion beam techniques. Host garnet and zircon contain numerous pockets of multiple inclusions, which consist of 1,3 diamond crystals intergrown with quartz, phengite, phlogopite, albite, K-feldspar, rutile, apatite, titanite, biotite, chlorite and graphite in various combinations. Recalculation of the average chemical composition of the entrapped fluid represented by multiple inclusion pockets indicates that such fluid contained a low wt% of SiO2, suggesting a relatively low-temperature fluid rather than a melt. Transmission electron microscopy revealed that the diamond contains abundant nanocrystalline inclusions of oxides, rare carbonates and silicates. Within the 15 diamond crystals studied, abundant inclusions were found of SiO2, TiO2, FexOy, Cr2O3, ZrSiO4, and single grains of ThxOy, BaSO4, MgCO3, FeCr2O4 and a stoichiometric Fe-rich pyroxene. The diversity of trace elements within inclusions of essentially the same stoichiometry suggests that the Kokchetav diamond crystallized from a fluid containing variable amounts of Si, Fe, Ti, Cr, Zr, Ba, Mg and Th and other minor components such as K, Na, P, S, Pb, Zn, Nb, Al, Ca, Cl. Most of the components in crystals included in diamond appear to have their origin in the subducted metasediments, but some of them probably originate from the mantle. It is concluded that Kokchetav diamond most likely crystallized from a COH-rich multicomponent supercritical fluid at a relatively low temperature (hence the apparently low content of rock-forming elements), and that the diversity of major and minor components suggests interactions between subducted metasediments and mantle components. [source] Screening of cosolvents for a supercritical fluid: A fully predictive approachAICHE JOURNAL, Issue 3 2002K. Abaroudi Solubility of solids was modeled in modified supercritical carbon dioxide as a predictive method. The Peng-Robinson equation of state was used to characterize the ternary systems using the one-fluid van der Waals rules. Ternary mixture parameters k12, k23, and k13 were obtained from the binary mixtures using Wong-Sandler mixing rules or the linear combination of Vidal-Michelsen mixing rules together with UNIFAC as required as a fully predictive tool for the liquid activity coefficients. When this method was applied to predict the solubility of ,-naphthol in CO2 modified with 6% and 10% toluene, values for the predicted solubility were very similar to the measured ones, with deviations of 9.6 and 26.3%, respectively. However, when the method was applied to the data of Simon et al. who examined six common cosolvents, the results were not as good in absolute terms, but the solvents were sorted in about the same order as found experimentally. The method provides quite an approximate guide to judge the most effective cosolvent from several candidates using a fully predictive methodology. [source] Supercritical fluid extraction of ecdysterone from the roots of Achyranthes bidentata BL.JOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2008Yizhe Zheng Abstract Ecdysterone has been found in a great many plants and animals and has some valuable pharmaceutical properties. The present study was conducted to investigate optimal conditions for the extraction of the compound by supercritical fluid extraction from the roots of Achyranthes bidentata BL. An orthogonal array design (OAD), OA9(34), was employed as a chemometric method for optimization of the extraction of ecdysterone from the herbal medicine. Four parameters, namely, pressure and temperature of the supercritical fluid, the dynamic extraction time, and the flow rate of dimethyl sulfoxide, were studied and optimized by a three-level OAD. Determinations of the extracts were performed by high-performance liquid chromatography. The effects of the parameters were studied using analysis of variance. The results shown that the yield of ecdysterone could be influenced by the four parameters to a similar degree. The yield for DMSO-modified supercritical CO2 was in the range from 0.65 to 1.03 mg/g under the selected conditions. In comparison with methanol-modified supercritical CO2 and Soxhlet extraction, a higher yield was obtained when DMSO-modified supercritical CO2 was used. [source] Supercritical carbon dioxide extraction of sea buckthorn (Hippophae rhamnoides L.) pomaceJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2007Dániel Cossuta Abstract BACKGROUND: The goal of this work was to utilize the sea buckthorn pomace, which is the by-product of a sea buckthorn juice process. Pilot plant supercritical fluid extraction (SFE) experiments were performed in a 5 × 10,3 m3 volume high-pressure vessel. The effects of pressure and temperature on extraction yield and recoveries of biologically active components were studied using a 32 full factorial design. The pressure and temperature were varied over the ranges of 30,46 MPa and 313,353 K, respectively. The extract samples were analysed by TLC-densitometry, UV/VIS spectrofotometry and HPLC methods. RESULTS: The obtained yields changed between 142,164 g kg,1, according to the solvent power of the supercritical fluid. The recoveries of the different minor components were (g minor components kg,1 dried raw material): 2.50,4.25 sitosterol, 0.20,1.60 ursolic acid, 0.04,0.18 carotenoid, 0.35,0.42 total tocopherol. CONCLUSION: By evaluation the designed experiments 46 MPa and 333 K were chosen as the optimum conditions. Copyright © 2007 Society of Chemical Industry [source] Electrochemistry at High Pressures: A ReviewELECTROANALYSIS, Issue 10 2004Debora Giovanelli Abstract High pressure electrochemical studies are potentially dangerous and less immediately implemented than conventional investigations. Technical obstacles related to properties of the working electrode material, preparation of its surface, availability of suitable reference electrodes, and the need for specially designed high pressure equipment and cells may account for the relative lack of experimental data on electrochemistry at high pressures. However, despite the stringent requirements for system and equipment stability, significant developments have been made in recent years and the combination of electrochemical methods with high hydrostatic pressure has provided useful insights into the thermodynamics, kinetics, and other physico-chemical characteristics of a wide range of redox reactions. In addition to fundamental information, high pressure electrochemistry has also lead to a better understanding of a variety of processes under non-classical conditions with potential applications in today's industrial environment from extraction and electrosynthesis in supercritical fluids to measurement of the pH at the bottom of the ocean. The purpose of this article is to detail the experimental pressurizing apparatus for electroanalytical measurements at high pressures and to review the relevant literature on the effect of pressure on electrode processes and on the properties of aqueous electrolyte solutions. [source] Aqueous fluids at elevated pressure and temperatureGEOFLUIDS (ELECTRONIC), Issue 1-2 2010A. LIEBSCHER Abstract The general major component composition of aqueous fluids at elevated pressure and temperature conditions can be represented by H2O, different non-polar gases like CO2 and different dissolved metal halides like NaCl or CaCl2. At high pressure, the mutual solubility of H2O and silicate melts increases and also silicates may form essential components of aqueous fluids. Given the huge range of P,T,x regimes in crust and mantle, aqueous fluids at elevated pressure and temperature are highly variable in composition and exhibit specific physicochemical properties. This paper reviews principal phase relations in one- and two-component fluid systems, phase relations and properties of binary and ternary fluid systems, properties of pure H2O at elevated P,T conditions, and aqueous fluids in H2O,silicate systems at high pressure and temperature. At metamorphic conditions, even the physicochemical properties of pure water substantially differ from those at ambient conditions. Under typical mid- to lower-crustal metamorphic conditions, the density of pure H2O is , the ion product Kw = 10,7.5 to approximately 10,12.5, the dielectric constant , = 8,25, and the viscosity , = 0.0001,0.0002 Pa sec compared to , Kw = 10,14, , = 78 and , = 0.001 Pa sec at ambient conditions. Adding dissolved metal halides and non-polar gases to H2O significantly enlarges the pressure,temperature range, where different aqueous fluids may co-exist and leads to potential two-phase fluid conditions under must mid- to lower-crustal P,T conditions. As a result of the increased mutual solubility between aqueous fluids and silicate melts at high pressure, the differences between fluid and melt vanishes and the distinction between fluid and melt becomes obsolete. Both are completely miscible at pressures above the respective critical curve giving rise to so-called supercritical fluids. These supercritical fluids combine comparably low viscosity with high solute contents and are very effective metasomatising agents within the mantle wedge above subduction zones. [source] Synthesis of Carbon-Nanotube Composites Using Supercritical Fluids and Their Potential ApplicationsADVANCED MATERIALS, Issue 7 2009Zhimin Liu Abstract Carbon-nanotube (CNT) composites have attracted a lot of attention because of their potential applications in many fields. Here, recent advances in the synthesis of CNT composites using supercritical fluids (SCFs) are highlighted. SCFs exhibit unique features for the synthesis of composites because of their unusual properties, such as low viscosity, high diffusivity, near-zero surface tension, and tunability. Preliminary studies show that SCFs show unusual advantages for the synthesis of CNT composites. The morphologies and structures of the resultant CNT composites can be tuned by changing the solvent properties. The SCF methods not only provide a green route for the synthesis of composites, but also result in nanostructures that have not yet been produced by conventional methods. Moreover, the potential applications of the resultant CNT composites are also discussed. [source] Supercritical Fluid,Liquid,Solid (SFLS) Synthesis of Si and Ge Nanowires Seeded by Colloidal Metal Nanocrystals,ADVANCED MATERIALS, Issue 5 2003T. Hanrath Abstract Semiconductor nanowires, 5 to 20 nm in diameter and micrometers in length, appear to be promising candidates for a variety of new technologies, including computing, memory, and sensor applications. Suitable for these applications, silicon (Si) and germanium (Ge) nanowires ranging from 4 to 30 nm in diameter and micrometers in length can be produced in high temperature supercritical fluids by thermally degrading organosilane or organogermane precursors in the presence of organic-monolayer-protected gold nanocrystals. Although gas phase vapor,liquid,solid (VLS) methods can be used to produce a variety of different nanowire materials, high temperature supercritical fluids provide wire size control through nanocrystal size selection prior to synthesis, and high product yields due to the high precursor solubility. [source] Advancement of Fischer-Tropsch synthesis via utilization of supercritical fluid reaction mediaAICHE JOURNAL, Issue 4 2010Nimir O. Elbashir Abstract The Fischer Tropsch Synthesis (FTS) reaction has been studied and for nearly a century for the production of fuels and chemicals from nonpetroleum sources. Research and utilization have occurred in both gas phase (fixed bed) and liquid phase (slurry bed) operation. The use of supercritical fluids as the reaction media for FTS (SCF-FTS) now has a 20-year history. Although a great deal of progress in SCF-FTS has been made on the lab scale, this process has yet to be expanded to pilot or industrial scale. This article reviews the research activities involving supercritical FTS and published in open literature from 1989 to 2008. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Supercritical fluids in medical radioisotope processing and chemistry, Part II: Applications , real and demonstratedJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2003Richard A. Ferrieri Abstract In Part I of this review series, an overview was presented on what the basic properties of supercritical fluids are and how they can, and are being used in many of today's industries as solvents for extraction, chromatography and reaction. A good part of this overview detailed the kinds of equipment needed, and techniques on how to use them for optimal performance. Part II of this series will delve into specific applications of supercritical fluid technology as it relates to aspects of medical isotope processing. The reader will note that very few applications of this technology to Nuclear Medicine have been published. Many potential applications cited within the context of this review derive from preliminary studies carried out in the author's laboratory. These examples are presented to spark interest in future developments of this nature. Copyright © 2003 John Wiley & Sons, Ltd. [source] Preparation of budesonide/,-cyclodextrin complexes in supercritical fluids with a novel SEDS methodJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2006Tarja Toropainen Abstract The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and ,-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80°C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% ,-CD aqueous solution. Solid, white budesonide/,-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60°C) the yield of the powder was 65,±,12% with 0.14,±,0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93,±,2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41,±,10%) and SEDS-processed budesonide without CD (61,±,3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2235,2245, 2006 [source] Cefuroxime axetil solid dispersions prepared using solution enhanced dispersion by supercritical fluidsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2005Seoung Wook Jun Cefuroxime axetil (CA) solid dispersions with HPMC 2910/PVP K-30 were prepared using solution enhanced dispersion by supercritical fluids (SEDS) in an effort to increase the dissolution rate of poorly water-soluble drugs. Their physicochemical properties in solid state were characterized by differential scanning calorimeter (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectrometry (FT-IR) and scanning electron microscopy. No endothermic and characteristic diffraction peaks corresponding to CA were observed for the solid dispersions in DSC and PXRD. FTIR analysis demonstrated the presence of intermolecular hydrogen bonds between CA and HPMC 2910/PVP K-30 in solid dispersions, resulting in the formation of amorphous or non-crystalline CA. Dissolution studies indicated that the dissolution rates were remarkably increased in solid dispersions compared with those in the physical mixture and drug alone. In conclusion, an amorphous or non-crystalline CA solid dispersion prepared using SEDS could be very useful for the formulation of solid dosage forms. [source] Nanometer-scale surface modification by polymerization of tetrafluoroethylene on polymer substrates in supercritical fluoroformJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008Toshiaki Mori Abstract Surface penetrated polymerization of tetrafluoroethylene (TFE) was carried out on a polycarbonate (PC) plate in supercritical fluoroform (scCHF3). Since the high diffusiveness is one of peculiar features of supercritical fluids, TFE monomers and initiators (perfluorinated benzoyl peroxide) could penetrate into the surface of polymer substrates and be photo-polymerized. After washing physisorbed homopolymers on the surface, polytetrafluoroethylene (PTFE) was found to penetrate into 50,800 nm depth from the surface and covered the PC surface in the proportion of 85%. The surface coverage density and the penetration depth could be controlled by adjusting of the pressure of scCHF3. The TFE-penetrated polymerization could be applied for various polymer plates such as polyethylene, polystyrene, polypropylene, poly(ethylene terephthalate), and polyimide. In addition to polymer plates, this technique could be applied to a cellulose paper, a nylon textile, and a porous PC membrane. The PTFE-penetrated nylon textile showed a high resistance for washing test with detergents, compared with the commercial fluoropolymer-sprayed nylon textile. The PTFE-penetrated porous PC membrane showed high oxygen permeability (P/P = 5.2), compared with that of the untreated PC membrane (P/P = 3.5) in gas permeation experiments of O2 and N2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1577,1585, 2008 [source] Enantiomeric composition studies in Lavandula species using supercritical fluidsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2005Gema Flores Abstract Characteristic aroma compounds in plants and essential oils of Lavandula from different varieties were examined. The study of the qualitative and quantitative composition of the major volatile components was faced by developing a method based on the use of supercritical fluid extraction-GC-MS (SFE-GC-MS). The optimization of a variety of parameters affecting SFE extraction enabled RSDs from three replicates lower than 2% to be achieved. Equally, recoveries of up to 59% were obtained by applying the proposed method. The use of multidimensional GC was necessary to enantiomerically resolve the target compounds. The obtained results showed enantiomeric purities >90% for all studied compounds in all varieties considered, proving the natural invariability of the enantiomeric composition of the compounds of interest. This information can be useful in authenticity studies as well as in selecting natural sources of enantiomerically pure compounds. [source] Automated Digital Image Based Measurement of Boundary Fractal Dimension for Complex NanoparticlesPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 1 2003Ramitha Wettimuny Abstract There is a growing realization that complex nanoparticles produced by combustion reaction, precipitation, and spray technology using supercritical fluids, are fractally structured. The boundary fractal dimension is linked to the flow, packing and consolidation dynamics of nanopowders. It also contains information on the formation dynamics of the nanoparticles produced by various methods. Extraction of the fractal dimension information embodied in the nanoparticle's fractal structure is hampered by the lack of automated characterization algorithms for processing images of particles. This paper describes an efficient algorithm for analyzing digitized images of fractally structured nanoparticles and presents a computer program that automates the procedure using digital image processing techniques. The program functionality is demonstrated and discussed using digital images of typical pigment, ceramic and pharmaceutical powders. [source] A novel equation of state (EOS) for prediction of solute solubility in supercritical carbon dioxide: Experimental determination and correlationTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009Sh. Jafari Nejad Abstract Solubility data of organophosphorous metal extractants in supercritical fluids (SCF) are crucial for designing metal extraction processes. We have developed a new equation of state (EOS) based on virial equation including an untypical parameter as BP/RT, reduced temperature and pressure for prediction of solute solubility in supercritical carbon dioxide (SC CO2). Solubility experimental data (solubility of tributylphosphate in SC CO2) were correlated with the two cubic equations of state (EOS) models, namely the Peng,Robinson EOS (PR-EOS) and the Soave,Redlich,Kwong EOS (SRK-EOS), together with two adjustable parameter van der Waals mixing and combining rules and our proposed EOS. The AARD of our EOS is significantly lower than that obtained from the other EOS models. The proposed EOS presented more accurate correlation for solubility data in SC CO2. It can be employed to speed up the process of SCF applications in industry. Les données de solubilité d'extractants de métaux organo-phosphorés dans des fluides supercritiques (FSC) sont cruciales pour concevoir des processus d'extraction des métaux. Nous avons développé une nouvelle équation d'état (ÉÉ) basée sur une équation d'état du viriel comprenant un paramètre atypique tel que la température et la pression réduite pour la prédiction de la solubilité du soluté dans du dioxyde de carbone supercritique. Les données expérimentales de solubilité (solubilité du phosphate de tributyle dans CO2 SC) ont été corrélées avec les deux modèles d'équations d'état cubiques, soit l'ÉÉ Peng,Robinson (ÉÉ-PR) et l'ÉÉ Soave,Redlich,Kwong (ÉÉ-SRK), avec deux paramètres ajustables, les règles de mélange et de combinaison van der Waals et notre ÉÉ proposée. L'AARD de notre ÉÉ est significativement plus faible que celui obtenu à partir des autres modèles d'ÉÉ. L'ÉÉ proposée présentait une corrélation plus exacte pour les données de solubilité dans le CO2 SC. Elle peut être employée pour accélérer les processus des applications de FSC dans l'industrie. [source] | ||||||||||||||||||||||||||||