Supercritical water extractions extract analysis

Agricirltrrral shell samples (walnut, almond, hazelnut cotton cocoon, and sunflower shells) were subjected to supercritical water extraction for producing hydrogen-rich gas mixtrrres (Demirbas, 2004). Table 6.10 shows stractrrral analysis results of the shell samples. In a typical nm of this study, the autoclave was loaded with a 5.0 g... 

Supercritical fluid extraction (SFE) and Solid Phase Extraction (SPE) are excellent alternatives to traditional extraction methods, with both being used independently for clean-up and/or analyte concentration prior to chromatographic analysis. While SFE has been demonstrated to be an excellent method for extracting organic compounds from solid matrices such as soil and food (36, 37), SPE has been mainly used for diluted liquid samples such as water, biological fluids and samples obtained after-liquid-liquid extraction on solid matrices (38, 39). The coupling of these two techniques (SPE-SFE) turns out to be an interesting method for the quantitative transfer... 

Supercritical fluid extraction (SFE) is generally used for the extraction of selected analytes from solid sample matrices, but applications have been reported for aqueous samples. In one study, recoveries of 87-100% were obtained for simazine, propazine, and trietazine at the 0.05 ug mL concentration level using methanol-modified CO2 (10%, v/v) to extract the analytes, previously preconcentrated on a C-18 Empore extraction disk. The analysis was performed using LC/UV detection. Freeze-dried water samples were subjected to SFE for atrazine and simazine, and the optimum recoveries were obtained using the mildest conditions studied (50 °C, 20 MPa, and 30 mL of CO2). In some cases when using LEE and LC analysis, co-extracted humic substances created interference for the more polar metabolites when compared with SFE for the preparation of the same water sample. ... 

The aim of the present work was to design and operate an apparatus in which stationary combustion and flames can be produced and sustained to pressures of 2000 bar and with environmental temperatures up to 500°C. Visual observation of the interior of the reaction vessel should be possible. Arrangements had to be made by which a gas flow of only a few microlitres per second could be fed steadily into the reaction vessel at pressures to two kilobar. A similar provision was necessary to extract small samples for product analysis at constant conditions. The principle of design and operation will be described. First results will be given for experiments with oxygen introduced into supercritical water-methane mixtures. 

In their test system, the researchers used the ionic liquid l-butyl-3-methylimidazol-ium hexafluorophosphate (bmim)(PF6), which is stable in the presence of oxygen and water, with naphthalene as a low-volatility model solute. Spectroscopic analysis revealed quantitative recovery of the solute in the supercritical CO2 extract with no contamination from the ionic liquid. They found that CO2 is highly soluble in (bmim)(PF6) reaching a mole fraction of 0.6 at 8 MPa, yet the two phases are not completely miscible. The phase behavior of the ionic liquid-C02 system resembles that of a cross-linked polymer-solvent system (Moerkerke et al., 1998), even though... 

Before the extraction procedure may commence, the sample must be prepared in such a way that it is in a condition for extraction of the analyte(s). For analyzing sulfonamide residues in liquid samples such as milk, a pretreatment dilution step with water prior to direct fluorometric detection may be required (207). Dilution of milk with aqueous buffer (208) or sodium chloride solution (209) prior to sample cleanup has also been reported. For the analysis of honey a simple dissolution of the sample in water (210, 211) or aqueous buffer (212) is generally required. Semisolid samples such as muscle, kidney, and liver, require, however, more intensive sample pretreatment. The analyte(s) must be exposed to extracting solvents to ensure maximum extraction. The most popular approach for tissue break-up is through use of a mincing and/or homogenizing apparatus. Lyophilization (freeze-drying) of swine kidney has been carried out prior to supercritical-fluid extraction of trimethoprim residues (213). 

Solid-phase extractions can reduce solvent consumption in analytical chemistry. For example, a standard procedure approved by the U.S. Environmental Protection Agency for the analysis of pesticides in wastewater requires 200 mL of dichloromethane for the liquid-liquid extraction of 1 L of water. The same analytes can be isolated by solid-phase extraction on C g-silica disks. The pesticides are recovered from the disks by supercritical fluid extraction with C02 that is finally vented into a small volume of hexane. This one kind of analysis can save 10s kg of CH2C12 per year.24... 

The application of SCF to the extraction of vitamins has been widely reported. Thus, retinyl palmitate and tocopherol acetate have been extracted from a hydrophobic ointment with supercritical CO2 at 40°C and 196 bar for 4 min, the extract analysis being performed by SFC (137). The calibration graphs were linear from 0.5 to 2.5 pg and the recoveries were quantitative. On the other hand, water-soluble vitamins can be extracted mixing them with low substituted hydroxypropil cellulose. Portions were placed in a column to which a reversed micellar extractant was delivered (138). Extraction of vitamins A and E and their esters from tablet preparations prior to FIPLC was performed in the dynamic mode with CO2 at 40°C and 253 bar for 15 min (139). Calibration graphs were linear from 0.02 to 0.8 and from 0.005 to 0.2 mg/mL of vitamins E and A, respectively. The corresponding RSDs (six... 

Similarly, the decomposition of rubber with supercritical water has been investigated by Funazukuri et alP5 Treatment of rubber with water at temperatures of about 380 °C led to a conversion of 43 48% of the raw tyre into oil. Elementary analysis showed that about half of the sulfur contained in the original sample is extracted into the oil, whereas the other half remains in the solid residue. 

Analysis of plants normally involves a sample preparation stage such as extraction or distillation followed by analysis with gas chromatography or liquid chromatography. The common methods used currently for the isolation of essential oils from natural products are steam distillation and solvent extraction (Ozel Kaymaz, 2004). Losses of some volatile compounds, low extraction efficiency, degradation of xmsaturated compounds through thermal or hydrolytic effects, and toxic solvent residue in the extract may be encountered with these extraction methods. Recently, more efficient extraction methods, such as supercritical fluid extraction (SFE) (Simandi et al., 1998) and accelerated solvent extraction (ASE) (Schafer, 1998) have been used for the isolation of organic compounds from various plants. Subcritical or superheated water extraction (SWE) is non-toxic, readily available, cheap, safe, non-flammable and is a recyclable option. 

See also Air Analysis Sampling. Extraction Solvent Extraction Multistage Countercurrent Distribution Supercritical Fluid Extraction. Gas Chromatography Multidimensional Techniques. Mass Spectrometry Time-of-Flight. Quality Assurance Quality Control Reference Materials. Water Analysis Overview. 

Microwave-Assisted Solvent Extraction Pressurized Fluid Extraction Supercritical Fluid Extraction Solid-Phase Extraction Solid-Phase Microextraction. Gas Chromatography Overview, Mass Spectrometry Environmental Applications. Immunoassays Overview. Liquid Chromatography Overview Reversed Phase Size-Exclusion Liquid Chromatography-Mass Spectrometry. Pesticides. Supercritical Fluid Chromatography Overview Applications. Thin-Layer Chromatography Overview. Water Analysis Organic Compounds. 

See also Carbohydrates Overview. Extraction Solid-Phase Extraction Supercritical Fluid Extraction. Food and Nutritional Analysis Sample Preparation Antioxidants and Preservatives Mycotoxins Oils and Fats. Lip-Ids Overview. Peptides. Proteins Overview. Toxins Mycotoxins Neurotoxins. Vitamins Overview Fat-Soluble Water-Soluble. 

The present work consists of a comparative study of three different extraction techniques—specifically, liquid-liquid extraction (LLE), solid-phase extraction (SPE), and supercritical fluid extraction (SEE)—for the trace analysis of fipronil insecticide in water samples. The extracted fipronil was analyzed via high-resolution gas chromatography using electron capture detection (HRGC-ECD). The extraction methods presented linear calibration all over the investigated concentration range (0.1-1.0 pg/L). The limit of detection (LOD) was determined at 0.1 pg/L concentration level, and precision, measured by the relative standard deviations (RSD), was 7.7% for LLE, 7.8% for SPE, and 0.5% for SEE. 

Studies of the source of exposure to PFCs have rarely been conducted. Thus, studies of the source of contamination with PFC, the source of exposure, the difihision path, the accumulated form, and toxicity are necessary. Currently, environmental contaminant of PFCs were mainly reported in polluted mud, ° environmental water, ° and atmosphere. However, the concentrations of detected PFCs are extremely low, and it is not sufficient to evaluate them as an exposure source. Therefore, we focused on house and carpet dust, ° which exists in our daily lives and contains many chemicals, to clarify the source of e xisure to PFCs, and discussed a highly sensitive and accurate method for the analysis of PFCs in house and carpet dust. The analytes were PFOS, PFOA, PFNA, and PFHxS, which are frequently detected in human blood, and surrogate standards were C4-PFOS and Cx-PFOA. The supercritical fluid extraction (SFE) method was used for house and carpet dust. Effective extraction is expected when supercritical liquid is used as the extraction solvent, as the elution ability of supercritical liquid is similar to that of conventional liquid and supercritical fluid can permeate every comer of the sample, as air does. 

Solid-phase extraction (SPE) using small, disposable cartridges, columns, or disks is employed for isolation and cleanup of pesticides from water and other samples prior to TLC analysis, especially using reversed-phase (RP) octa-decyl (C-18) bonded silica gel phases. Microwave-assisted extraction (MAE) is a time- and solvent-saving method for removing residues from samples such as soils. Supercritical fluid extraction (SEE) has been used for sample preparation in the screening of pesticide-contaminated soil by conventional TLC and automated multiple development (AMD). Ultrasonic solvent extraction (USE) and videodensitometry have been combined for quantification of pesticides in sod. Matrix solid-phase dispersion (MSPD) with TLC and GC has been used to determine diazinon and ethion in nuts. 

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