Enrichment of the thymoquinone content in volatile oil from Satureja montana using supercritical fluid extraction

Supercritical fluid extraction (SFE) of the volatile oil from Satureja montana L. was performed under different conditions of pressure (90 and 100 bar), temperature (40 and 50°C), mean particle sizes (0.4, 0.6 and 0.8 mm) and CO₂ flow rate (0.8, 1.1 and 1.3 kg/h) to understand the influence of these parameters on the composition and yield of this oil. The results were compared with those obtained for the essential oil isolated by hydrodistillation (HD). The volatile and the essential oil were analysed by GC and GC‐MS. The main compounds are carvacrol (52.2–62.0% for HD vs. 41.7–64.5% for SFE), thymol (8.6–11.0% for HD vs. 6.0–11.3% for SFE), p‐cymene (6.9–12.8% for HD vs. 6.0–17.8% for SFE), γ‐terpinene (6.4–9.4% for HD vs. 2.3–6.0% for SFE) and β‐bisabolene (2.0–2.7% for HD vs. 2.2–3.5% for SFE). The major difference between SFE and HD was the relative amount of thymoquinone, an oxygenated monoterpene with important biological activities, which can be ten‐fold higher in volatile oil (1.6–3.0 for SFE vs. 0.2% for HD). The morphology of the glandular trichomes of S. montana and the effect of the grinding process on them was also evaluated by SEM.     

Supercritical fluid extraction of Kava lactones from Kava root and their separation via supercritical fluid chromatography

Summary Seven Kava lactones were extracted from Kava root using both pure and 15% ethanol modified CO₂. Most of the Kava lactones were extracted employing 100% CO₂ with an efficiency greater than 90% relative to conventional solvent extraction using organic solvents. Extraction efficiency did not increase significantly when using 15% ethanol-modified CO₂ as an extraction fluid. Separation of extracted Kava lactones was obtained using various packed columns and methanol-modified CO₂. An optimized separation was achieved using either an amino or protein C₄ column at 125 atm and 80°C. Semi-preparative separation of Kava lactones was also obtained using two columns connected in series.     

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 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 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 carbon dioxide extraction of Mentha pulegium L. essential oil

The dependence of Mentha pulegium L. (pennyroyal) essential oil composition, obtained by supercritical carbon dioxide (SC-CO₂), with the following parameters: pressure, temperature, extraction time (dynamic), and modifier (methanol) was studied. The results were also compared with those obtained by conventional hydrodistillation method in laboratory conditions. Regarding the percentages of menthone (30.3%) and pulegone (52.0%), the optimum SFE results were obtained at the following experimental conditions: pressure=100 atm, T=35 °C, dynamic time=10 min, and V_modifier=0 μl. The results of hydrodistillation showed that the major components of M. pulegium L. were pulegone (37.8%), menthone (20.3%), and piperitenone (6.8%). The evaluation of the composition of each extract was performed by gas chromatography-mass spectrometry.     

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 flumetralin in tobacco

Summary This work evaluates the level of Flumetralin residues in real tobacco samples. Conventional extraction methods were compared with SFE methods in both static and dynamic modes using CO₂ and CO₂ with modifier. Additionally, in the dynamic SFE mode, different collection approaches, such as collection at room temperature without solvent, collection at room temperature in the presence of solvent (hexane) and collection in an ice bath, without solvent, were studied. SFE showed itself to be a promising extraction technique for pesticide residues in tobacco samples.     

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 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.     

Composition and antioxidant activity of Thymus vulgaris volatiles: Comparison between supercritical fluid extraction and hydrodistillation

Supercritical fluid extraction (SFE) of the volatile oil from Thymus vulgaris L. aerial flowering parts was performed under different conditions of pressure, temperature, mean particle size and CO₂ flow rate and the correspondent yield and composition were compared with those of the essential oil isolated by hydrodistillation (HD). Both the oils were analyzed by GC and GC‐MS and 52 components were identified. The main volatile components obtained were p‐cymene (10.0–42.6% for SFE and 28.9–34.8% for HD), γ‐terpinene (0.8–6.9% for SFE and 5.1–7.0% for HD), linalool (2.3–5.3% for SFE and 2.8–3.1% for HD), thymol (19.5–40.8% for SFE and 35.4–41.6% for HD), and carvacrol (1.4–3.1% for SFE and 2.6–3.1% for HD). The main difference was found to be the relative percentage of thymoquinone (not found in the essential oil) and carvacryl methyl ether (1.0–1.2% for HD versus t?0.4 for SFE) which can explain the higher antioxidant activity, assessed by Rancimat test, of the SFE volatiles when compared with HD. Thymoquinone is considered a strong antioxidant compound.     

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 polychlorinated dibenzo-p-dioxins from municipal incinerator fly ash

The supercritical fluid extraction of polychlorinated dibenzo-p-dioxins from an incinerator fly ash sample has been investigated; supercritical nitrous oxide and its mixtures with methanol and toluene were employed as mobile phases. Recoveries of individual polychlorinated dibenzo-p-dioxins congeners were calculated from results of analysis of ¹³C-labeled dioxins by high resolution GC-MS employing selected ion monitoring. The extraction procedure was compared with extraction in a Soxhlet apparatus, which is currently used as a standard method for removing chlorinated dibenzo-p-dioxins from fly ash samples: the results indicated that the time required for the extraction and clean-up can be reduced from 24 to 2.5 hours/sample. Quantitative recovery of the chlorinated dibenzo-p-dioxins was achieved at μg/kg levels, the relative standard deviation was between 1.8 and 5.8%. The use of a virtually inert fluid such as pure nitrous oxide provides significant improvement over conventional extraction procedures because no solvent residue is left in the processed extract.     

Supercritical fluid extraction of the fluoroquinolones norfloxacin and ofloxacin from orally treated-chicken breast muscles

Supercritical fluid extraction (SFE) of the fluoroquinolones norfloxacin and ofloxacin from chicken breast muscles was examined. A liquid chromatography with fluorescence detection was used for the determination of the fluoroquinolones. Extraction conditions of the SFE were optimized by determining the extraction parameters to achieve a sufficiently high recovery of each fluoroquinolone in fortified-muscle samples. Recovery values for the extraction of the fluoroquinolones using the SFE ranged from 70 to 87%. Chickens were treated orally with each fluoroquinolone and their muscles were extracted at set time intervals for time-course determination of the fluoroquinolones in chickens. The SFE combined with liquid chromatographic analysis showed that the concentrations of the fluoroquinolones decreased gradually with time in the chicken muscles after oral treatment, giving a concentration less than 5 ng/ml in 120 h. No further sample cleanup procedures were required after the SFE. These results suggest that SFE method is an extraction method for the determination of norfloxacin and ofloxacin in chicken muscle.     

Supercritical fluid extraction of kava lactones from Piper methysticum (kava) herb

Supercritical fluid extraction of kava lactones from Piper methysticum Forst. herb is described here. The extraction was performed with supercritical carbon dioxide alone and supercritical carbon dioxide modified with 15% ethanol, and the extracts were analyzed by gas chromatography/mass spectrometry. Seven lactones including: 7,8-dihydrokavain; kavain; 5,6-dehydrokavain; 5, 6, 7, 8-tetrahydroyangonin; dihydromethysticin; yangonin; and methysticin were the major constituents in the SFE extract.     

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 Moroccan (Timahdit) oil shale with water

Timahdit oil shale was subjected to supercritical water extraction. The results reveal significant difference in oil yields and composition when compared with those obtained from conventional pyrolysis. In addition, the effect of temperature and residence time on the supercritical water extraction of oil was investigated in a set of three experiments. The results revealed that the yield and the fraction of paraffins and aromatics increase while the percentage of asphaltenes decreases as the temperature is increased from 380 to 400°C. The residence time was found to affect the yield and the fraction of asphaltenes and polar compounds.     

Dynamics of chelation-supercritical fluid extraction from wood fibers

The dynamics of supercritical fluid extraction (SFE) of the metal content of wood fibers chelated with lithium bis(trifluoroethyl) dithiocarbamate (FDDC) by supercritical (SF) CO2 was investigated experimentally by monitoring the spectra of the eluted metal complex as a function of time. The characteristic shape of the dynamic SFE curve was determined mainly by the flow conditions in the extraction vessel, the mass transfer resistance in the SF phase, and the solubility. High extraction yields of metal content were obtained in two-stage extraction including static (batch) and dynamic (semi-batch) stages. Increasing the length of the static stage increased the rate of dynamic elution of metal complex until it approached the dynamics of fluid displacement for a continuous stirred tank reactor (CSTR). In such cases, increasing the flow rate had no effect on the dynamic extraction curve when it was plotted using dimensionless time. Efficient chelation-SFE from wood fibers was obtained at a pressure of 20.3 MPa and with a static time of 30 min.