Supercritical fluid extraction ofCymbopogon citratus (DC.) Stapf

Summary Cymbopogon citratus (DC.) Stapf. is also known as lemon grass; its leaves produce a volatile oil upon steam extraction which is used for medicinal purposes. This work describes the supercritical fluid extraction ofCymbopogon citratus in sequential and dynamic extraction modes. Different modifiers for supercritical carbon dioxide were used for the extractions. Principal compounds in the essential oils were analyzed by GC and GC-MS and identified as neral, geraniol, geranial, nerolic acid and geranic acid. Different chromatographic profiles were obtained when the type and proportion of modifier were changed.     

High-performance liquid chromatography analysis of four Leuzea carthamoides flavonoids

A simple and sensitive high-performance liquid chromatography method for the determination of four Leuzea carthamoides flavonoids, namely eriodictyol, patuletin, eriodictyol-7-beta-glucopyranoside, and 6-hydroxykaempferol-7-O-(6"-O-acetyl-beta-D-glucopyranoside), is presented. Using this method, quantitative composition of flavonoids ranged from 0.011% to 0.574% in dried plant material was determined. This method could be used in the future for the quantitative evaluation of major phenolic compounds in L. carthamoides.     

Supercritical fluid extraction

Supercritical fluid extraction (SFE) provides for the first time a viable option to conventional and widely used Soxhlet extraction. The ability to change the solvating power of a single supercritical fluid by changing its density is an exceedingly attractive feature. An environmentally safe alternative such as supercritical carbon dioxide to organochlorine solvents which are widely used today in many government and industrial analytical laboratories for sample preparation is desirable. SFE may also constitute a viable alternative to other popular sample preparation techniques such as liquid-liquid extraction, solid phase extraction and purge/trap. Much research, however, must be done in order to understand, optimize and apply this technology. For example, (a) automation of extraction, (b) matrix effects, (c) new fluids/modifiers/additives, (d) trapping efficiency, (e) recovery of extracted analytes, and (f) extraction kinetics are some areas which need a greater understanding. This review is concerned with many of these topics as they relate to trace organic analysis wherein SFE is the primary sample preparation technique.     

Supercritical fluid extraction of Beauvericin from maize

Beauvericin (BEA), a supercritical fluid extraction with supercritical carbon dioxide from maize was investigated. Extraction efficiencies under several different extraction conditions were examined. Pressure, temperature, extraction time, organic modifier and water matrix content (10%) were investigated. The best extraction conditions were at a temperature of 60 °C, 3200 psi, for 30 min static extraction time and methanol as modifier solvent. Extraction recovery of 36% without modifier by adding water to the matrix in the extraction vessel (reproducibility relative standard deviations (R.S.D.)=3-5%) were recorded. Extraction recovery of 76.9% with methanol as co-solvent (reproducibility R.S.D.=3-5%) was obtained. Data shows that SFE gives a lower BEA recovery compared to conventional extraction protocol with organic solvents while SFE with modifier and conventional extraction yields are comparable. BEA extract contents were determined by high pressure liquid chromatography (HPLC) with a diode array detector (DAD) at 205 nm and BEA peak confirmed by LC-MS. Acetonitrile-water as mobile phase and column C-18 were both tested. Instrumental and analytical parameters were optimized in the range linear interval from 1 to 500 mg kg⁻¹ and reached a detection limit of 2 ng.     

Supercritical fluid extraction of flavonoids from Scutellariae Radix

An optimal condition of supercritical fluid extraction (SFE) for flavonoids of Scutellaria baicalensis was developed. In this study, various temperatures, pressures and modifiers were studied. The conventional extraction methods were conducted in parallel for comparison. The crude extracts were qualitatively compared by TLC and GC–MS, and the contents of flavonoids were determined by HPLC. The amounts of baicalin, baicalein and wogonin in the Scutellariae Radix obtained by supercritical fluid extraction and a conventional sonic shaking method were 137.6 mg/g, 8.6 mg/g and 2.2 mg/g, 113.5 mg/g, 5.7 mg/g and 2.3 mg/g, respectively. Application of SFE for extraction of the flavonoids from Scutellariae Radix was preferable. The optimal conditions of SFE was as follows: supercritical carbon dioxide–MeOH–water (20:2.1:0.9), 50°C and 200 bar.     

Supercritical fluid extraction of oxadixyl from food crops

Summary This work describes the study of a degradation curve of Oxadixyl in field-treated potato and tomato samples. The residues were extracted using classical and supercritical fluid (SFE) extraction methods and analyzed by HRGC/ECD. The extraction techniques were compared and the results indicate the advantages of using SFE as an alternative method for pesticide analyses in these samples.     

Supercritical fluid extraction of pesticides

Summary The extraction behaviour of 10 g samples of five pesticides and some related compounds from glass wool with supercritical CO₂ has been investigated under several conditions (10 MPa, 20 MPa extraction pressure, 313 K, dry and water saturated CO₂). The extraction fluid was decompressed over a line of little columns, filled with 3 Si₆0 or RP18, and the amount of deposited material was analyzed by HPLC for each of these columns. Due to the progressive pressure/density reduction along the line, the solubility diminishes and hence the compounds are deposited according to their polarity/vapor pressure earlier or later on the line. Thus extraction and prefractionation of compounds of different polarity take place in one sample preparation step.

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Extraktion von Pesticiden mit überkritischen fluiden PhasenI. Extraktionseigenschaften von ausgewählten Pesticiden in CO₂

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Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet     

Supercritical fluid extraction of carbamate pesticides from soils and cereals

Summary A method for the supercritical fluid extraction of carbamate pesticides (propoxur, aminocarb, carbaryl and methiocarb) from soil and cereal samples using CO₂ is proposed. Extractions were at 378 bar and 54 °C. Analytes were determined in the extracts by HPLC with fluorescence detection after post-column derivatization. Recoveries from spiked soil ranged between 39.6 and 91.7%, depending on analyte and soil components. Lowest recoveries were from sandy soils. Aminocarb could not be recovered from any soil using CO₂. Recovery of aminocarb from diatomaceous earth was improved by adding methanol to the extraction cell prior to SFE, but the effect was not observed in soil samples. Recoveries for propoxur and aminocarb from spiked wheat were about 75%, and only between 30–50% for aminocarb from corn and oats, and carbaryl from wheat. Fat was coextracted using CO₂ and retained in the trap together with the analytes, however, appropriate rinsing solvent allowed on-line clean-up of the extract.     

Supercritical fluid extraction of 2,3,7,8-tetrachlorodibenzo-p-dioxin from sediment samples

Supercritical fluid extraction (SFE) is a promising technique for the extraction of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) from environmental matrices such as contaminated sediments. The ability of SFE to solubilize many organic contaminants is well documented in industrial processes but its analytical applications were exploited just recently. In this study supercritical carbon dioxide and nitrous oxide and their mixtures with 2% methanol were used to extract 2,3,7,8-TCDD from aquatic sediments. An attractive feature of this process is that the carbon dioxide, being a virtually inert fluid, leaves no solvent residue on the processed sediment. Almost 100% of the 2,3,7,8-TCDD can be extracted from a sediment spiked with 200 μg/kg 2,3,7,8-TCDD in 30 minutes by using supercritical carbon dioxide + 2% methanol. Cleanup procedure is compared with the Soxhlet extraction procedure currently used as a standard method for extracting dioxins from sediment samples.     

Supercritical fluid extraction of triazine herbicides from solid matrices

Summary Several investigations were performed to optimise the extraction of polar triazine herbicides using supercritical fluid extraction from two different solid matrices: C₁₈-silica and soil samples. Supercritical CO₂ modified with methanol [10% (VV)] at 250 bars and 50°C was required to quantitatively extract Atrazine and 2-Hydroxyatrazine from spiked C₁₈-silica. Extraction of Desisopropyl-desethyl-2-hydroxyatrazine (MET) attained only 52%, even following addition of water to the polar modifier. Extractions of spiked soil samples (20 ppm of each pesticide) were successful at 300 bars and 65°C. A non polar wash improved the recoveries of the three target analytes [i.e. atrazine: 88%; 2-hydroxyatrazine: 96%; MET: 41%]. The extraction parameters employed are discussed in this paper.     

Supercritical fluid extraction of phenol compounds from olive leaves

A clean, highly selective supercritical fluid extraction (SFE) method for the isolation of phenols from olive leaf samples was examined. Total phenol extracts were determined using the Folin-Ciocalteu reagent. Dried, ground, sieved olive leaf samples (30 mg) are subjected to SFE, using carbon dioxide modified with 10% methanol at 334 bar, 100 degrees C (CO(2) density 0.70 g ml(-1)) at a liquid flow-rate of 2 ml min(-1) for 140 min. Diatomaceous earth is used to reduce the void volume of the extraction vessel. The influence of extraction variables such as modifier content, pressure, temperature, flow-rate, extraction time, and collection/elution variables, were studied. Supercritical fluid extracts were screened for acid compounds such as carboxylic acids and phenols using Electrospray-MS (in the negative ionization mode). SFE was found to produce higher phenol recoveries than sonication in liquid solvents such as n-hexane, diethyl ether and ethyl acetate. However, the extraction yield obtained was only 45%, using liquid methanol.     

Supercritical fluid extraction of atrazine and its metabolites from soil

Soxhlet (methanol) and SFE extraction with carbon dioxide in the presence of modifiers at different temperatures (100–200°C) for the extraction of atrazine and its main metabolites from a soil sample were compared. The most effective extraction conditions for both atrazine and its metabolites (i.e. deethylatrazine and deisopropylatrazine) were Co₂ modified with 20% molar methanol-trifluoroacetic acid (MeOH-TFA) (TFA 0.65M in MeOH) at 100°C, leading to an extraction efficiency comparable with that of Soxhlet extraction with MeOH for atrazine and ca. 20% higher for its main metabolites. The relative standard deviation (RSD) of SFE was lower than that obtained by Soxhlet extraction, probably because of less interference in the cGC-NPD determination. All the other modifiers evaluated (acetone, triethylamine, and methanol) were less effective than MeOH-TFA for the extraction of atrazine and its metabolites from a soil sample, even at high molar concentrations (20%) and use of higher extraction temperatures (200°C). These results indicate the importance of matrix effects and the need of the selection of an appropriate modifier in order to obtain quantitative extractions by SFE.     

Supercritical fluid extraction of oxindole alkaloids from Uncaria tormentosa

Supercritical fluid extraction of oxindole alkaloids from Uncaria Tormentosa is described. The extraction was performed with supercritical carbon dioxide alone and with supercritical carbon dioxide modified with 10% metanol, and the extracts were analyzed by GC/MS and HPLC/MS.     

Supercritical fluid extraction of mercury species

Supercritical fluid extraction was used to recover organic and inorganic mercury species. Variations in pressure, water, methanol, and chelator create methods that allowed separation of inorganic from organic mercury species. When extracted using a compromised set of extraction conditions, the order of extraction was methyl, phenyl and inorganic mercury. For the individually optimized conditions, quantitative recoveries were observed. Level as low as 20 ppb were extracted and then determined using ICP.     

Supercritical fluid extraction of organic and inorganic mercury from solid materials

Mercuric ions (Hg(2+)) can be extracted from solid samples (cellulose matrix) using methanol modified supercritical CO(2) containing the fluorinated chelating agent lithium bis(trifluoroethyl)dithiocarbamate (LiFDDC). Methylmercuric chloride (CH(3)HgCl) and dimethylmercury [(CH(3))(2)Hg] can be extracted by supercritical CO(2) without chelating agent and modifier. The solubility of Hg(FDDC)(2) in supercritical CO(2) has been determined to be 5 x 10(-3)M at 5O degrees C and 150 atm, which is about 3 orders of magnitude greater than that of the non-fluorinated analogue Hg(DDC)(2). Use of methanol (5%)-modified CO(2) further enhances the solubility of Hg(FDDC)(2) by a factor of 2.4. A small amount of water added to the sample matrix tends to facilitate the extraction of Hg(FDDC)(2) and CH(3)HgCl. Potential applications of this in situ chelation-supercritical fluid extraction method for the preconcentration of mercury species and treatment of mercury contaminated wastes are discussed.     

Supercritical fluid extraction of the volatile oil from Santolina chamaecyparissus

Supercritical fluid extraction (SFE) of the volatile oil from Santolina chamaecyparissus L. flower heads was performed under different conditions of pressure, temperature, mean particle size and CO₂ flow rate. This oil was compared with the essential oil isolated by hydrodistillation (HD). The SFE volatile and essential oils were analysed by GC and GC‐MS. The range of the main volatile components obtained with HD and SFE were, respectively: 1,8‐cineole (25–30% and 7–48%), camphor (7–9% and 8–14%), borneol (7–8% and 2–11%), terpinen‐4‐ol (6–7% and 1–4%), terpinolene (1–4% and 1–7%) and isobornyl acetate (1–2% and 1–11%). The chemical composition of the extracts was greatly influenced by the conditions of pressure and temperature used. In fact, it was possible to enrich the sesquiterpene fraction by increasing the pressure from 8 to 9 MPa, while changing the temperature from 40 to 50°C at 90 bar enriched of the volatiles in n‐alkanes.