Search results for "Supercritical"

Innovative “Green” and Novel Strategies for the Extraction of Bioactive Added Value Compounds from Citrus Wastes—A Review

2017

Citrus is a major processed crop that results in large quantities of wastes and by-products rich in various bioactive compounds such as pectins, water soluble and insoluble antioxidants and essential oils. While some of those wastes are currently valorised by various technologies (yet most are discarded or used for feed), effective, non-toxic and profitable extraction strategies could further significantly promote the valorisation and provide both increased profits and high quality bioactives. The present review will describe and summarize the latest works concerning novel and greener methods for valorisation of citrus by-products. The outcomes and effectiveness of those technologies such a…

Structure of diblock copolymers in supercritical carbon dioxide and critical micellization pressure

1999

This paper reports a small angle neutron scattering investigation of micelle formation by fluorocarbon-hydrocarbon block copolymers in supercritical ${\mathrm{CO}}_{2}{(\mathrm{s}\mathrm{c}\ensuremath{-}\mathrm{C}\mathrm{O}}_{2})$ at 65 \ifmmode^\circ\else\textdegree\fi{}C. A sharp unimer-micelle transition is obtained due to the tuning of the solvating ability of ${\mathrm{s}\mathrm{c}\ensuremath{-}\mathrm{C}\mathrm{O}}_{2}$ by profiling pressure, so that the block copolymer, in a semidilute solution, finds ${\mathrm{s}\mathrm{c}\ensuremath{-}\mathrm{C}\mathrm{O}}_{2}$ a good solvent at high pressure and a poor solvent at low pressure. At high pressure the copolymer is in a monomeric state…

Reversed Phase Liquid Chromatography

2015

Supercritical fluid extraction and high performance liquid chromatography determination of homosalate in lipsticks

2001

Supercritical fluid extraction of homosalate is reported for the first time. Extraction parameters such as pressure, time of extraction, use of modifier, temperature and sample mass were studied. The proposed method was assayed for the extraction of homosalate in sunscreen lipsticks. Efficient recoveries were obtained after 5 min of dynamic extraction with supercritical CO2 and 15% ethanol as modifier at 300 bar and 60°C, flow rate 4 mL min−1. Extracts were dissolved in ethanol, and homosalate determined by HPLC using water—acetic acid—ethanol mobile phase and flow rate of 1 mL min−1. UV detection was at 309 nm using homosalate in ethanol solutions as standards, limit of detection 4 μg mL−1…

Supercritical fluid chromatography in drug analysis: A literature survey

1996

The applications of supercritical fluid chromatography to the analysis of drugs have been carefully revised from the literature compiled in the Analytical Abstracts until March 1994. Easy-to-read tables provide useful information about the state-of-the-art and possibilities offered by SFC in pharmaceutical analysis. The tables comprise extensive data about samples analyzed, pharmaceutical principles determined, solvents used and sample quantity injected, supercritical fluids and modifiers employed, injection system, instrumentation, experimental conditions for chromatographic separations (density, pressure, flow, temperature), characteristics of columns employed (type, support, length, diam…

Supercritical fluid extraction of resveratrol from grape skin of Vitis vinifera and determination by HPLC

2000

Supercritical fluid extraction of resveratrol from grape skin of Vitis vinifera was studied. Extraction variables such pressure, modifier concentration (ethanol), and extraction time were optimised. Final extraction conditions were: 40 degrees C, 150 bar, 7.5% ethanol and extraction time 15 min. Extraction recovery and precision (variation coefficient between 0.2 and 1.0%) were calculated. The resveratrol content in the ethanolic extract was determined by HPLC with UV detection at 306 nm. Acetic acid-methanol-water was used as the mobile phase, and C-18 and C-8 columns were tested, instrumental parameters were optimised, and analytical parameters were calculated (lineal interval 0-75 mg l(-…

On critical behaviour in generalized Kadomtsev-Petviashvili equations

2016

International audience; An asymptotic description of the formation of dispersive shock waves in solutions to the generalized Kadomtsev–Petviashvili (KP) equation is conjectured. The asymptotic description based on a multiscales expansion is given in terms of a special solution to an ordinary differential equation of the Painlevé I hierarchy. Several examples are discussed numerically to provide strong evidence for the validity of the conjecture. The numerical study of the long time behaviour of these examples indicates persistence of dispersive shock waves in solutions to the (subcritical) KP equations, while in the supercritical KP equations a blow-up occurs after the formation of the disp…

Influence of the pH on the ZnO nanoparticle growth in supercritical water: Experimental and simulation approaches

2014

Abstract In order to improve the knowledge on the nucleation and the growth mechanisms of metal oxides nanoparticles produced in supercritical water domain, ZnO was used as a “model” material. A continuous process of hydrothermal synthesis was employed to synthesize ZnO nanopowders ( T  = 410 °C and P  = 305 bar) from Zn(NO 3 ) 2 and KOH solutions with different values of [KOH]/[Zn(II)] ratio from 0 to 8 in order to investigate the pH effect on the growth of ZnO nanocrystallite in terms of size and morphology. The samples were characterized by X-Ray Diffraction and Transmission Electronic Microscopy. ZnO crystal was considered as a cylindrical crystallite with a diameter D and height H . Es…

Analysis of Dissolved-Gas Atomization: Supercritical CO2 Dissolved in Water

2010

Supercritical dissolved-gas atomization is an atomization process in which carbon dioxide at temperature and pressure above its critical point is used as the atomizing gas. The spray characteristics in terms of droplets size and distribution have been experimentally studied using a laser diffraction method based on a Malvern apparatus. The main parameter that influences the droplets size is the gas-to-liquid mass ratio (GLR); the injection pressure in the range of 7.4-13 MPa has a minor effect. Upon variation of the GLR from 0.5 to 3, the droplet mean diameter changes from about 8.0 to 2.0 μm; very narrow droplet size distributions are also produced. From the point of view of the atomizatio…

Peracetylated β‐cyclodextrin as solubilizer of arylphosphines in supercritical carbon dioxide

2006

Abstract Effect of peracetylated β-cyclodextrin on the solubility of diphenyl(4-phenylphenyl)phosphine in supercritical carbon dioxide medium has been investigated. As shown by gravimetric measurements, the presence of cyclodextrin (CD) (1 equivalent) allows to increase the solubility of phosphine (P) in supercritical carbon dioxide (scCO 2 ) (40 °C, 35.2 MPa, nominal system density 0.89 g/mL). This solubility enhancement was attributed to host–guest interactions in scCO 2 as the P was recovered in the form of an inclusion complex. Furthermore, a diffuse reflectance spectroscopy study on the samples recovered after the experiments and on various CD/P solid mixtures obtained by co-grinding i…