Screening of pesticide-contaminated soil by supercritical fluid extraction (SFE) and high-performance thin-layer chromatography with automated multiple development (HPTLC/AMD)

A method for screening of pesticide-contaminated soil was developed. The extraction is carried out by supercritical carbon dioxide (CO₂) with methanol as a modifier. The different components of the extracts are separated by high-performance thin-layer chromatography with automated multiple development (HPTLC/AMD) and evaluated densitometrically. The technique can be carried out without any previous clean-up step. Compared with other extraction techniques, SFE has the advantages of reducing the amount of co-extracted soil contents, which can seriously deteriorate the results. A 35-step development of the TLC-plate with gradient elution offers an application over a wide range of polarity. Migration data for 107 pesticides, recoveries and detection limits for 20 pesticides were determined.     

Screening of pesticide-contaminated soil by supercritical fluid extraction (SFE) and high-performance thin-layer chromatography with automated multiple development (HPTLC/AMD)

A method for screening of pesticide-contaminated soil was developed. The extraction is carried out by supercritical carbon dioxide (CO(2)) with methanol as a modifier. The different components of the extracts are separated by high-performance thin-layer chromatography with automated multiple development (HPTLC/AMD) and evaluated densitometrically. The technique can be carried out without any previous clean-up step. Compared with other extraction techniques, SFE has the advantages of reducing the amount of co-extracted soil contents, which can seriously deteriorate the results. A 35-step development of the TLC-plate with gradient elution offers an application over a wide range of polarity. Migration data for 107 pesticides, recoveries and detection limits for 20 pesticides were determined.     

Specific extraction of chromium(VI) using supercritical fluid extraction

In some situations, it is no longer sufficient to give a total concentration of a metal. Instead, what is required to understand the potential toxicity of a sample is the concentration of metal species or oxidation state. When developing species specific methods, the major concern is that the integrity of the species ratio is not changed. In other words, the sample preparation or the analytical method will not convert metal ions from one oxidation state to another. Normal extraction techniques and chromatography methods have shown some tendencies to change species ratios. An ideal extraction method would extract the metal efficiently while retaining the metal's oxidation state. The properties of supercritical fluids should approach the ideal of retention of oxidation states. For example, the need for speciation of chromium is obvious since Cr(III) is considered an essential element while Cr(VI) is thought to be toxic and carcinogenic. This paper presents the results of a species specific extraction of Cr(VI) using two different carbamate derivatives as the chelator. Supercritical fluid extraction (SFE) coupled with a fluorinated dithiocarbamate and a methanol modifier allows extraction of 1 ppm Cr(VI) from a solid matrix with a recovery level of 88.4+/-2.57% using the NIST standard sample. The optimized conditions using the HP 7680 supercritical fluid extractor were: 0.1 ml of methanol, 0.05 ml of pure water, and 0.01 g of chelate via a saturation chamber.     

Certification of the aflatoxin B1 content in animal feed Reference Materials and intercomparison with supercritical fluid extraction (SFE)

Summary Intercomparison studies allowed an improvement in aflatoxin B₁ analysis and the development of procedural quality criteria. These led to a successful evaluation of the certification exercise on the aflatoxin B₁ content in five animal feed RMs. The 1st intercomparison study on supercritical fluid extraction (SFE) techniques gave very helpful explanations to solve matrix difficulties.     

Supercritical fluid extraction (SFE) as a multi-residue extraction procedure for beta-agonists in bovine liver tissue

A supercritical fluid extraction procedure has been developed for the extraction of beta-agonists in bovine liver samples. The method is suitable for compounds of different beta-agonist classes: the substituted aniline-type compounds (e.g. clenbuterol) and the phenolic-type compounds (e.g. salbutamol), including conjugated forms of the latter. The developed procedure involves a combination of supercritical fluid extraction with enzyme immunoassay for the determination of clenbuterol and salbutamol residues at the low ppb level. Addition of methanol modifier and removal of sample moisture are necessary for the extraction of more polar analytes such as salbutamol. Method validation incorporating intra- and inter-assays was carried out on fortified liver tissue and showed good recovery and low variation (RSD < 15%). An enzyme hydrolysis procedure was incorporated into the method for the deconjugation of conjugated residues. The developed procedure was shown to be successful for the determination of both clenbuterol and salbutamol in incurred liver tissue.     

Grape seed oil extraction: Interest of supercritical fluid extraction and gas-assisted mechanical extraction for enhancing polyphenol co-extraction in oil

The aim of this study is to compare three oil extraction methods and to evaluate their efficiency for producing an oil rich in polyphenols. The three extraction methods are screw pressing, extraction by supercritical CO₂ percolation and the combination of these two processes (Gas-Assisted Mechanical Expression: GAME). Screw pressing is the most efficient process for producing grape seed oil with a high yield, but supercritical CO₂ process permits an increase of polyphenol co-extraction with oil. The GAME process allows extraction of more polyphenols than screw pressing and constitutes an interesting process considering oil yield.     

超临界萃取川芎精油的GC-MS分析

不同压力和温度条件下超临界萃取所得川芎精油的收率不同,通过气相色谱-质谱联用对精油的挥发性成分进行分析,结果表明不同条件下超临界萃取所得川芎精油的主要挥发性成分相似,但其质量分数有一些差别.     

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.     

Isolation of palm tocols using supercritical fluid chromatography

Crude palm oil contains 600 to 1000 ppm of tocols in the form of tocopherols and tocotrienols. These palm tocols have been isolated and analyzed in the past by various chromatographic techniques such as open column chromatography, high-performance liquid chromatography, as well as thin-layer chromatography. Supercritical fluid chromatography (SFC) has emerged as a more advanced chromatographic technique in recent years. The tocols present in palm oil are successfully isolated using SFC. Identification of these tocols is supported by various spectroscopic techniques such as 1H NMR, 13C NMR, and mass spectrometry.     

Chemicals from forest products by supercritical fluid extraction

Supercritical acetone or methanol extraction of wood gave liquid products with a maximum yield of 74%. Approximately 5% of these complex products was identified as substituted guaiacols and levoglucosan. Acetone extract could substitute for 30% of the phenol in phenolic resins.

Resin and fatty acids were extracted from southern pine and waxes from Douglas-fir bark using supercritical carbon dioxide, nitrous oxide, propane or ethylene. Of these, propane and nitrous oxide gave the best yields.     

超临界流体萃取法对有机锡化合物的选择性萃取

 研究了用超临界流体萃取法直接从脂肪基质的固体样品（大豆粉）中选择性地萃取有机锡化合物的方法。模拟试样萃取结果表明：用较低压力和较高温度的超临界态ＣＯ２作流动相时，有机锡达到最大萃取率，而脂肪类物质仅被少量萃取，从而消除了脂肪类物质对超临界流体色谱法测定有机锡的干扰。     

Superheated water extraction, steam distillation and SFE of peppermint oil

Superheated water extraction, steam distillation and supercritical fluid extraction (SFE) are compared for extraction of l-menthol, menthone, eucalyptol and other components of peppermint (mentha piperita) leaves. Different temperatures and pressures were investigated. SFE results at 25/40 °C and 6.5/8/10 MPa were comparable with those reported in the literature. Although SFE is a gentle way of extracting thermally unstable compounds, this method is too slow for commercial use in comparison with steam distillation at 100 °C. Superheated water extraction at 125/150 °C and 1–2 MPa exhibits higher extraction efficiency than the SFE method. Comparison of all experiments under the chosen conditions shows steam distillation to be the most effective extraction method. Received: 18 January 1998 / Revised: 9 April 1999 / Accepted: 15 April 1999     

Superheated water extraction, steam distillation and SFE of peppermint oil

Superheated water extraction, steam distillation and supercritical fluid extraction (SFE) are compared for extraction of l-menthol, menthone, eucalyptol and other components of peppermint (mentha piperita) leaves. Different temperatures and pressures were investigated. SFE results at 25/40?°C and 6.5/8/10 MPa were comparable with those reported in the literature. Although SFE is a gentle way of extracting thermally unstable compounds, this method is too slow for commercial use in comparison with steam distillation at 100?°C. Superheated water extraction at 125/150?°C and 1–2 MPa exhibits higher extraction efficiency than the SFE method. Comparison of all experiments under the chosen conditions shows steam distillation to be the most effective extraction method.     

Some applications of supercritical fluid extraction

Supercritical fluid extraction (SFE) exploits the solvation power of fluids at temperatures and pressures close to their critical point. Use of SFE with supercritical CO₂ is reported for the extraction of caffeine and quinine from various plant materials and of morphine from serum. Results are compared with those obtained by extractions with subcritical methanol and tetrahydrofuran, normal organic Soxhlet extractions and solid-phase extraction.     

Improved supercritical fluid extraction of sulphonamides

Summary Different ways used for enhancing the yield of sulphonamides leached from solid supports are reported. Supercritical CO₂ and methanol-modified CO₂ were used as extractants of the target analytes and the impregnation of the solid sample with buffer, derivatization of the analytes and ion-pair formation were assessed. Only the sulphonamide/tetramethyl-ammonium ion-pairs are quantitatively extracted from the solid supports using pure supercritical CO₂, while the other modifications and the presence of a cosolvent lead to recoveries lower than 30% for most of the analytes. Individual separation/quantitation of the analytes was performed off-line using a liquid chromatograph.