Showing papers on "Extraction (chemistry) published in 2000"
TL;DR: This review gives a brief theoretical background of microwave heating and the basic principles of using microwave energy for extraction, and attempts to summarize all studies performed on closed-vessel MAE until now.
953 citations
TL;DR: In this paper, the authors describe laboratory procedures for the determinations of bioavailable (e.g., plants) quantities of nutritional and polluting inorganic elements in 0.01 M CaCl2 extracts of air-dry soil samples.
Abstract: This publication gives details of laboratory procedures for the determinations of bioavailable (e.g., plants) quantities of nutritional and polluting inorganic elements in 0.01 M CaCl2 extracts of air‐dry soil samples. Air‐day soil samples are extracted for two hours with a 0.01 M CaCl2 solution of 20°C in a 1:10 extraction ratio (W/V). After measuring the pH in the settling suspension, the concentrations of nutritional and polluting elements are measured in the clear centrifugate or filtrate. The procedure is simple, easy to perform, and cheap (labor, chemicals) in daily use in routine soil laboratories. The method receives internationally more and more attention as an alternative for the many extraction procedures for a single nutrient or pollutant that are still in use nowadays. The soil is extracted with a solution what has more or less the same ionic strength as the average salt concentration in many soil solutions. Various nutrients and metals can be measured in a single extract that allows...
720 citations
TL;DR: In recent years, microwave assisted extraction has attracted growing interest as it allows rapid extractions of solutes from solid matrices, with extraction efficiency comparable to that of the classical techniques as mentioned in this paper.
Abstract: In recent years, microwave-assisted extraction has attracted growing interest as it allows rapid extractions of solutes from solid matrices, with extraction efficiency comparable to that of the classical techniques. In particular, numerous applications of this recent technique deal with the extraction of pollutants from environmental samples. This review gives a brief presentation of the theory of microwave and extraction systems, a discussion of the main parameters that influence the efficiency, and the main results on the applications to environmental matrices. Finally, the performance of this technique is compared to that from classical extractions (sonication and Soxhlet extraction) and recent techniques (supercritical fluid extraction and accelerated solvent extraction).
454 citations
TL;DR: The results suggest that fatty acid analysis methodology for microheterotrophs under consideration for biotechnological exploitation requires optimisation and validation.
416 citations
TL;DR: In this paper, the authors provided additional data on a sewage sludge amended soil certified reference material, CRM 483, which was certified in 1997 for its EDTA and acetic acid extractable contents of some trace metals, following standardised extraction procedures.
Abstract: This paper provides additional data on a sewage sludge amended soil certified reference material, CRM 483, which was certified in 1997 for its EDTA and acetic acid extractable contents of some trace metals, following standardised extraction procedures. The additional work aimed to test the long-term stability of the material and the applicability of an improved version of the BCR three-step sequential extraction procedure on the sewage sludge amended soil (CRM 483). The paper demonstrates the CRM 483 long-term stability for EDTA and acetic acid extractable contents of Cd, Cr, Cu, Ni, Pb and Zn and gives the results (obtained in the framework of an interlaboratory study) for the extractable contents of the same elements in the CRM 483, following the BCR three-step sequential extraction scheme. The aqua regia extractable contents following the ISO 11466 Standard are also given. The data are given as indicative (not certified) values.
363 citations
TL;DR: In this article, the use of an aqueous-based extraction technique utilizing hydroxypropyl-β-cyclodextrin (HPCD) is presented for the extraction of PAHs from soil.
Abstract: Traditionally, soil extraction techniques have been concerned with the determination of “total” organic contaminant concentrations, following an “exhaustive” extraction. However, in light of the increasing body of knowledge relating to organic contaminant availability and aging, such methods have little relevance to the amount of contaminant that may pose an ecological risk i.e., the “bioavailable” portion. Less exhaustive techniques have therefore been the subject of more recent approaches in the hope that they may access the “labile” or bioavailable pool. The use of an aqueous-based extraction technique utilizing hydroxypropyl-β-cyclodextrin (HPCD) is presented here for the extraction of PAHs from soil. The optimization of the method is described in terms of HPCD concentration, extraction time, and solution buffering. The procedure is then tested and validated for a range of 14C-labeled PAHs (phenanthrene, pyrene, and benzo[a]pyrene) added at a range of concentrations to a range of soil types. The amoun...
359 citations
TL;DR: In this paper, a factorial designed experiment was conducted to optimize supercritical fluid extraction (SFE) results for the isolation of lycopene and beta-carotene.
Abstract: Lycopene and beta-carotene were extracted from tomato paste waste using supercritical carbon dioxide (SC-CO(2)). To optimize supercritical fluid extraction (SFE) results for the isolation of lycopene and beta-carotene, a factorial designed experiment was conducted. The factors assessed were the temperature of the extractor (35, 45, 55, and 65 degrees C), the pressure of the extraction fluid (200, 250, and 300 bar), addition of cosolvent (5, 10, and 15% ethanol), extraction time (1, 2, and 3 h), and CO(2) flow rate (2, 4, and 8 kg/h). The total amounts of lycopene and beta-carotene in the tomato paste waste, extracts, and residues were determined by HPLC. A maximum of 53.93% of lycopene was extracted by SC-CO(2) in 2 h (CO(2) flow rate = 4 kg/h) at 55 degrees C and 300 bar, with the addition of 5% ethanol as a cosolvent. Half of the initially present beta-carotene was extracted in 2 h (flow rate = 4 kg/h), at 65 degrees C and 300 bar, also with the addition of 5% ethanol.
311 citations
TL;DR: In this article, a review of non-porous membrane extraction techniques is presented, including supported liquid membrane extraction, microporous membrane liquid-liquid extraction, polymeric membrane extraction and membrane extraction with a sorbent interface.
280 citations
TL;DR: In this paper, a four-stage sequential extraction procedure for determination of the speciation of extractable heavy metals, proposed by the Commission of the European Communities Bureau of Reference (BCR), has been applied to lake sediments collected from the lakes of a water-laden area of Sultansazliǧi, Kayseri, Turkey.
274 citations
TL;DR: The sulfuric acid treatment and silica gel/sulfuric acid column gave the highest yields for acid stable compounds, although a few target compounds were lost during that treatment and all compounds were recovered with the HR-GPC method.
Abstract: A method for the analysis of potential endocrine-disrupting compounds, such as phenolic halogenated compounds (e.g., chlorinated and brominated phenols) and hydroxylated PCBs, in blood plasma is presented. Neutral halogenated compounds, specifically brominated diphenyl ethers and PCBs, are also included in the evaluation. An efficient denaturation and extraction step is described, and three methods for lipid removal are evaluated. The latter includes a nondestructive method based on high-resolution gel permeation chromatography (HR-GPC), a newly developed silica gel/sulfuric acid column, and lipid removal by sulfuric acid treatment. Recoveries, based on gas chromatography with an electron capture detector (GC-ECD), were between 70 and 90% for most of the studied compounds. The recoveries of phenolic compounds were generally slightly lower than those of the neutral compounds. The sulfuric acid treatment and silica gel/sulfuric acid column gave the highest yields for acid stable compounds, although a few target compounds were lost during that treatment and all compounds were recovered with the HR-GPC method.
249 citations
TL;DR: The microspace in the microchannel was characterized by the large specific interface area and short diffusion distance, and these characteristics may contribute to highly efficient extraction without mechanical shaking and may lead to the integration of more complicated separation and chemical operations on a microchip and more applications.
Abstract: An ion-pair solvent extraction was performed in a microchannel fabricated in a quartz glass chip. The aqueous solution of Fe−bathophenanthrolinedisulfonic acid complex and the chloroform solution of tri-n-octylmethylammonium chloride were introduced into the microchannel, and a parallel two-phase laminar flow was formed. The ion-pair product extracted in chloroform was monitored by the thermal lens microscope. The ion-pair product was gradually extracted from aqueous solution into chloroform when the flow was very slow or stopped, while nothing was extracted into chloroform when the flow was fast. The time for extraction in the present 250 μm microchannel, 45 s, roughly coincided with the molecular diffusion time, and the extraction time was at least 1 order shorter compared with the ordinary extraction time using a separatory funnel and mechanical shaking. The microspace in the microchannel was characterized by the large specific interface area and short diffusion distance, and these characteristics may ...
TL;DR: In this article, the basic experimental set-up is presented, and parameters influencing the extraction process are discussed, and the potential for replacing tedious classic extraction methods such as Soxhlet extraction is discussed.
Abstract: This review updates our knowledge on pressurised liquid extraction, PLE (also known as accelerated solvent extraction and pressurised fluid extraction) of persistent organic pollutants such as polynuclear aromatic hydrocarbons and polychlorinated biphenyls from environmental matrices. The basic experimental set-up is presented, and parameters influencing the extraction process are discussed. PLE can be used for a broad range of applications, and clearly has the potential for replacing tedious classic extraction methods such as Soxhlet extraction.
TL;DR: The use of supercritical carbon dioxide as a substitute solvent for chemical synthesis and catalysis is a relatively new research area with significant potential as mentioned in this paper, however, it is difficult to evaluate the feasibility of using SCF solvents in a wide range of applications.
Abstract: Organometallic chemistry, chemistry of compounds containing metal–carbon bonds or compounds in which an organic molecule (sometimes with a net negative charge) is bonded to a metal atom through an oxygen or nitrogen atom, is one of the most rapidly growing areas of chemical research. Organometallic compounds are being extensively utilized as reagents in preparation and processing of advanced inorganic materials, as catalysts in production of a wide variety of chemicals and as chemotherapy drugs. Supercritical fluid (SCF) science and technology is another rapidly growing field due to the interesting and desirable properties of SCFs as solvents. The combination of organometallic chemistry and SCFs is a relatively new research area with significant potential. Some applications include (1) use of organotransition metal complexes as homogeneous catalysts for reactions in SCFs [D.A. Morgenstern, R.M. LeLacheur, D.K. Morita, S.L. Borkowsky, S. Feng, G.H. Brown, L. Luan, M.F. Gross, M.J. Burk, W. Tumas, Supercritical carbon dioxide as a substitute solvent for chemical synthesis and catalysis, in: P.T. Anastas, T.C. Williamson (Eds.), Green Chemistry: Designing Chemistry for the Environment, American Chemical Society, Washington, DC, 1996, p. 132 and G.P. Jessop, T. Ikariya, R. Noyori, Homogeneous catalysis in supercritical fluids, Science 269 (1995) 1065], (2) impregnation of polymers with various organometallic complexes from SCF solutions for property enhancement or for subsequent in-situ chemical transformations within such matrices [J.J. Watkins, T.J. McCarthy, Polymer/metal nanocomposite synthesis in supercritical CO2, Chem. Mater. 7 (1995) 1991, and A.I. Cooper, S.G. Kazarian, M. Poliakoff, Supercritical fluid impregnation of polyethylene films, a new approach to studying equilibria in matrices; the hydrogen bonding of fluoroalcohols to (η5-C5Me5)Ir(CO) and the effect on CH activation, Chem. Phys. Lett. 206 (1993) 175], (3) decomposition of organometallic complexes in SCFs for formation of inorganic powders with controlled size distribution [M. Barj, J.F. Bocquet, K. Chhor, C. Pommier, Submicronic MgAl2O4 powder synthesis in supercritical ethanol, J. Mater. Sci. 27 (1992) 2187], (4) SCF extraction of heavy metals from various matrices by formation of organometallic complexes [K.E. Laintz, C.M. Wai, C.R. Yonker, R.D. Smith, Extraction of metal ions from liquid and solid materials by supercritical carbon dioxide, Anal. Chem. 64 (1992) 2875]. At the University of Connecticut, our research efforts are concentrated on evaluation of technical and economical feasibility of some of these applications. The three primary research thrusts in our group have been the utilization of supercritical carbon dioxide (scCO2) as a solvent in rhodium catalyzed homogeneous hydroformylation reactions [D.R. Palo, C. Erkey, Homogeneous catalytic hydroformylation of 1-octene in supercritical carbon dioxide using a novel rhodium catalyst with fluorinated aryl phosphine ligands, Ind. Eng. Chem. Res. 37 (1998) 4203], impregnation of polyurethane foams with organometallic oxidants from scCO2 solutions and subsequent vapor phase polymerization in these foams for production of electrically conductive composite foams [Y. Fu, D.R. Palo, C. Erkey, R.A. Weiss, Synthesis of conductive polypyrrole/polyurethane foams via a supercritical fluid process, Macromolecules 30 (1997) 7611], and investigation of extraction of heavy metals from aqueous solutions by compound formation using scCO2 [J. Murphy, C. Erkey, Copper(II) removal from aqueous solutions by chelation in supercritical carbon dioxide using fluorinated β-diketones, Ind. Eng. Chem. Res. 36 (1997) 5371]. Advances in these areas greatly depend on our understanding the interactions of SCFs and organometallic complexes and how these interactions affect a particular application. The subject matter of this review is extraction of heavy metals from aqueous solutions in the presence of SCFs. Since solvent extraction of heavy metals is utilized on a commercial scale, the replacement of organic solvents by SCFs has been the major driving force behind our research efforts. Therefore, this review was prepared to highlight the areas important for commercial scale application of the technology. In Section 1, an introduction to solvent extraction of metals is given. A brief introduction to the possible advantages of using SCFs is also presented in the same section. The fundamentals of extraction with different types of extractants (cation exchangers, solvating extractants and ion-pair extractants) are given in Sections 2, 3 and 4, together with the studies in the literature on metal extraction using SCFs for each type of extractant. Thermodynamics of extraction is particularly emphasized due to its governing role in the economical feasibility of a large scale process. The experimental methods that are utilized in evaluation of thermodynamic behavior of such systems are provided in Section 5. The current methods to recycle the extractants are presented in Section 6. The kinetics of extraction is described in Section 7 where no studies using SCFs have been reported to date and a brief conclusion is provided in Section 8.
TL;DR: The results of the BCR three-step sequential extraction procedure indicate high Ni and Zn mobility in the sludge analysed, which means the investigated sewage sludge could not be used in agriculture.
TL;DR: In this article, soy and wheat bran were employed as raw materials for the production of pectinases by Aspergillus niger through solid-state fermentation, and several fermentation and recovery parameters were studied.
TL;DR: Findings presented in this study extend the existing fundamental knowledge related to sampling/sample preparation with SPME, thereby enabling the development of new sampling devices for the rapid sampling of air, headspace, water, and soil.
Abstract: A new, rapid air sampling/sample preparation methodology was investigated using adsorptive solid-phase microextraction (SPME) fiber coatings and nonequilibrium conditions for volatile organic compounds (VOCs). This method is the fastest extraction technique for air sampling at typical airborne VOC concentrations. A theoretical model for the extraction was formulated based on the diffusion through the interface between the sampled (bulk) air and the SPME coating. Parameters that affect the extraction process including sampling time, air velocity, air temperature, and relative humidity were investigated with the porous (solid) PDMS/DVB and Carboxen/PDMS coatings. Very short sampling times from 5 s to 1 min were used to minimize the effects of competitive adsorption and to calibrate the extraction process in the initial linear extraction region. The predicted amounts of extracted mass compared well with the measured amounts of target VOCs. Findings presented in this study extend the existing fundamental know...
TL;DR: The yields and compositions of lignin phenols from four different samples match those obtained by the "traditional" procedure, and there is a marked increase in the achievable sample throughput.
Abstract: A novel approach for the analysis of lignin in geochemical samples has been developed as an alternative to the alkaline CuO oxidation procedure first developed in 1982. The new procedure utilizes microwave digestion technology, as opposed to conductive heating, to carry out oxidative hydrolysis of six samples in an oxygen-free atmosphere at 150 °C for 90 min. Ethyl acetate is used as the extraction solvent in place of diethyl ether. Additionally, the new method incorporates a simplified extraction procedure that minimizes solvent handling and the amount of glassware needed. Under these novel conditions, the yields and compositions of lignin phenols from four different samples (modern and ancient sediments; woody and nonwoody tissues) match those obtained by the “traditional” procedure. The significant advantages of this new alkaline CuO oxidation method include faster reaction times, the ability to accurately measure and control reaction conditions, added flexibility for the analyst, and a marked increase...
TL;DR: The feasibility of application of mixtures of carbon dioxide and alcohol under supercritical conditions for selective extraction of some phenolic compounds from grape seeds has been studied and solvent capacity was found to increase with pressure and with the amount of alcohol used as cosolvent as expected.
Abstract: Proanthocyanidins are supposed to have some therapeutical properties as antioxidants and antineoplasics. Most of the proanthocyanidins, however, are not commercialized since their separation from natural sources is either very expensive or not well-known. In this work, the feasibility of application of mixtures of carbon dioxide and alcohol under supercritical conditions for selective extraction of some phenolic compounds from grape seeds has been studied, among them some low polymerized proanthocyanidins, their main monomer units, (+)-catechin and (−)-epicatechin, and some low molecular weight phenolic compounds, like gallic acid. An analytical-scale supercritical fluid extractor, whose operation was previously optimized, was used to carry out the experiments. A commercial concentrate of complex phenols and tannins from grape seeds was subjected to supercritical extraction in order to find the best operation conditions before directly extracting defatted milled grape seeds. The solvent capacity was found...
TL;DR: SDS-PAGE showed that LPS and lipid A isolated using the Tri-Reagent approach were cleaner and suffered less degradation through loss of phosphate and (or) fatty acyl side chains from lipid A.
Abstract: A fast, convenient extraction method for lipopolysaccharide (LPS), using a commercial RNA isolating reagent, allows the isolation of LPS or lipid A from low milligram (dry weight) quantities of bacterial cells. The method avoids the use of specialized equipment and has been used for processing relatively large numbers of samples. The major components of the commercial RNA isolating reagent, Tri-Reagent, are phenol and guanidinium thiocyanate in aqueous solution. The bacterial cell membranes are disrupted with guanidinium thiocyanate, which eliminates the need for mechanical cell disruption (e.g. French press) or heating. LPS and its degradation products, with particular attention paid to its bioactive lipid A portion, were measured and compared with those from the most common conventional extraction method, hot phenol-water. Negative ion quadrupole ion trap and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, fatty acid composition analysis by capillary gas chromatography, total and free phosphate by UV spectrophotometry and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that LPS and lipid A isolated using the Tri-Reagent approach were cleaner and suffered less degradation through loss of phosphate and (or) fatty acyl side chains from lipid A. The Tri-Reagent extraction method generated low free phosphate contamination, 11% of the total phosphate concentration, whereas the hot phenol-water extraction method gave approximately 58% as free, inorganic phosphate. Similar results were observed for the degradation of fatty acyl side chains. The time required by the new method is considerably shorter (two or three days) than that required by conventional hot phenol-water extraction (about two weeks).
TL;DR: It has been proved that the chromatographic features and the method of chemical expression of the concentrations may greatly affect the final values of polyphenolic compounds of the same oil.
Abstract: The extraction procedures (solid/liquid SPE and liquid/liquid LLE) and HPLC separation and quantification methods of polyphenolic compounds have been checked in virgin olive oils in order to explain the differences in content reported in the literature. The work has been carried out on oils prepared from one cultivar and produced under the same protocol. The extraction methods are practically equivalent, but the SPE technique is more favorable because it is faster and simpler. It has been proved that the chromatographic features and the method of chemical expression of the concentrations may greatly affect the final values. Thus, under the same analytical method, the total concentration values of polyphenols of the same oil show variations from 18% to 80%, according to the formality of expression as gallic acid, caffeic acid, or tyrosol equivalents. The role of the nature and spectrophotometric features of the phenols and of the internal standard is also discussed, and it was found to be an important source of reported variation. A gradient separation with an eluent mixture acetonitrile-sulfuric acid (0.1 mol/L), detection at 225 nm, and quantitative calculation of polyphenolic compounds in oils (expressed as tyrosol equivalents, THY(eq)) is proposed.
TL;DR: The combined gas chromatographic determination of a number of hydroxyl-group containing endocrine disruptors, including 4-octylphenol, 4-nonylphenol and 2,4-dichlorophenol, was investigated, finding limits of detection of were 4-6 ng/l but higher for the hormones.
TL;DR: Viscosity of barley flour slurries was affected by the content of soluble beta-glucans, beta-Glucanase activity, and molecular weight of beta- glucans.
Abstract: Total and soluble beta-glucan content and effects of various treatments of barley grain on extractability and molecular characteristics of soluble beta-glucan were studied. Four types of hulless barley (normal, high amylose, waxy, and zero amylose waxy) from 29 registered and experimental genotypes were analyzed. For each, moisture, protein, amylose, 100 kernel weight, starch, beta-glucan (total and soluble), beta-glucanase activity, and slurry viscosity were determined. Significant differences in total beta-glucan were observed among the groups, with average values of 7. 49%, 6.86%, 6.30%, and 4.38% for high amylose, waxy, zero amylose waxy, and normal barley, respectively. The extractability of beta-glucan in high amylose barley was relatively low (20.6-29.7%) compared to that in normal (29.8-44.3%), zero amylose waxy (34.0-52. 5%), and waxy (36.7-52.7%) barley genotypes. Viscosity of barley flour slurries was affected by the content of soluble beta-glucans, beta-glucanase activity, and molecular weight of beta-glucans. Hydrothermal treatments (autoclaving and steaming) of barley had no effect on extractability of beta-glucans, but prevented enzymic hydrolysis of beta-glucans, and thereby substantially improved their molecular weight. The addition of enzymes (protease and esterase) during extraction and/or physical treatments (sonication) increased extractability of beta-glucans from barley.
TL;DR: The size-exclusion (SE) HPLC profile of total protein extract obtained by sonication of flour samples at ambient temperature showed marked instability on reinjection as discussed by the authors, which was related to the presence of flour proteases that were inactivated by thermal treatment of the samples at 60°C.
Abstract: The size-exclusion (SE) HPLC profile of total protein extract obtained by sonication of flour samples at ambient temperature showed marked instability on reinjection. Instability was related to the presence of flour proteases that were inactivated by thermal treatment of flour samples at 60°C. Extraction of flour protein by sonication was a function of ultrasonic energy (sonication time × power product) delivered to flour sample. As protein solubility increased, the proportions of the earliest eluted SE-HPLC fractions (F1 and F2) increased. Oversonication of proteins evidenced by a decrease in F1 amount at the benefit of F2 occurred below the sonication energy level needed for total protein extraction. Ultrasonic energy level was adjusted to allow total protein extraction while limiting oversonication. The sonication procedure was applied on 27 flour samples of contrasting dough strength to extract total proteins. Absolute amount of protein extractable by sonication, determined from SE-HPLC area,...
TL;DR: The objective of this review is to provide updated information about the most important features of graphitized carbonaceous sorbents used for solid-phase extraction (SPE) of organic compounds from liquid natural matrices or extracts.
TL;DR: Solid-phase extraction (SPE) for two groups of polyaromatic compounds--polycyclic aromatic hydrocarbons and naphthalenesulfonates--with completely different problems in the extraction process are reviewed.
TL;DR: Results depend on factors such as the type of catalysis selected, the use of nonpolar solvents, heating applied during the synthesis, and the degree of suitability of the procedure chosen for the particular features of each sample.
Abstract: The development of methods for analyzing fatty acids that provide rapid and reliable results is currently in great demand. Recently, different lipid extraction procedures such as microwave or supercritical fluid extraction have been researched. Both procedures avoid the use of large volumes of solvents and provide rapid lipid isolations. Only a few papers have reported work on microwave extraction, but many studies about supercritical fluid extraction have been carried out and have been gaining acceptance within the scientific community. Avoiding the lipid isolation step, by synthesizing fatty acid esters by simultaneous lipid extraction and derivatization through in situ reactions, has also been proposed. The saving of time and reagents is significant. Owing to the differences among the procedures, some knowledge of their characteristics is essential in order to improve methods and achieve reliable and accurate results. Clearly, results depend on factors such as the type of catalysis selected, the use of nonpolar solvents, heating applied during the synthesis, and the degree of suitability of the procedure chosen for the particular features of each sample.
TL;DR: The recovery of GA from licorice root with MAE was equivalent with conventional extraction methods, which include extraction at room temperature (ERT), the traditional Soxhlet extraction, heat reflux extraction and ultrasonic extraction.
TL;DR: In this paper, a review of the literature on the solubility enhancement of solid mixtures in supercritical CO 2 is presented, where the phase behaviour of the solid mixture under high pressure and the effect of melting on the enhancement of solubilities are examined.
Abstract: A wealth of information on the solubility of materials in supercritical fluids (SCFs) has been published in the literature. For the most part, this information is concerned with the solubility of individual solutes in supercritical CO 2 (binary systems). It has become clear from the relatively few studies on the solubility of solid mixtures that binary solubility data represent a limited picture of the complex intermolecular interactions that may occur in the SCF phase. In particular, the solubility of a solid may be enhanced significantly, compared to its binary system, in the presence of a second solid. In this review, published data on the solubilities of solid mixtures in supercritical CO 2 are examined to highlight unique solubility phenomena associated with these systems. An extensive compilation of solubility enhancement data, the first of its kind, is presented for this purpose. The phase behaviour of solid mixtures under high pressure is considered as well as the effect of melting on solubility enhancement. The impact of solubility enhancement on selectivity is assessed and opportunities for improving the selectivity of extraction are highlighted. For most solid mixtures, solubility enhancement can be explained in terms of an entrainer effect similar to that observed in cosolvent systems. However, if the solid mixture partially melts, solubility enhancement becomes heavily dependent on which species is present as an excess solid phase. An examination of the phase behaviour of solid mixtures is therefore essential for the interpretation of solubility enhancement data.
TL;DR: The efficiency of pigment and fatty acid extraction from resistant algae using Scenedesmus obliquus as an example was examined and found that adding quartz sand and solvent to freeze-dried algal material and subsequent extraction in an ultrasound bath for 90min at −4 °C resulted in excellent extraction of these compounds.
Abstract: In this paper, the efficiency of pigment and fatty acid extraction from resistant algae using Scenedesmus obliquus as an example was examined. We found that adding quartz sand and solvent to freeze-dried algal material and subsequent extraction in an ultrasound bath for 90 min at 4C resulted in excellent extraction of these compounds. This extraction method was compared with a method regularly used for extraction of fatty acids and pigments, i.e. addition of solvents to algal material with subsequent incubation. Our extraction using the ultrasound and sand method was about twice as efficient as this method for both pigments and fatty acids. The ultrasound method is simple, extracts over 90% of the different substances in one step and conserves the relationships of pigments and fatty acids. In addition, no alteration- or breakdown products were observed with the new method. Thus, this method allows accurate quantitative extraction of both pigments and fatty acids from Scenedesmus obliquus and other algae. The method was also been found to be as effective for Cryptomonas erosa(Cryptophyceae), Cyclotella meneghiniana(Bacillariophyceae), Microcystis aeruginosa(Cyanophyceae), and Staurastrum paradoxum (Chlorophyceae, Desmidiaceae) and is thus applicable to a wide spectrum of algae.
TL;DR: In this paper, the results obtained by sequential extraction methods for Cu, Cr, Ni, Pb and Zn were compared with those estimated from single extractions using identical operating conditions, applied in each individual Tessier and BCR fraction.
Abstract: The conventional Tessier and BCR sequential extraction methods
were applied to metal partitioning in sewage sludge samples collected from
a waste water treatment plant. The results obtained by sequential
extraction methods for Cu, Cr, Ni, Pb and Zn were compared with those
estimated from single extractions using identical operating conditions
applied in each individual Tessier and BCR fraction. The metal content in
the extracts was measured by flame atomic absorption spectrometry. In all
fractions of the BCR method, and in the three first fractions of the
Tessier method, the results obtained from single extractions were in good
agreement with those obtained using the sequential procedures. The
oxidizable fraction of the Tessier method should be leached from the solid
residue of the reducible extraction, since a very low extraction efficiency
was obtained for this fraction when it was directly extracted. The total
extractable metal contents obtained by both single and sequential
extractions were similar for all metals in the BCR method and for Cr, Ni
and Pb in the Tessier method. The recoveries obtained ranged from 93.52 to
105.8% in the two studied samples. For Cu and Zn the overall extraction
efficiency of the proposed method was slightly lower than that obtained
with the sequential procedure (recoveries around 90%). The precision of the
proposed Tessier and BCR single extraction methods (expressed as RSD) was
lower than 8% for all metals.