Solvent extraction methanol

Cow s milk (congener specific) Mixing of sample fortified with C-labeled PCBs with sodium oxalate and methanol solvent extraction cleanup and HRGC/MS 0.1-0.5 pg/g (fat) for tetra- to hexa-congeners of PCB 50-60 Van der Velde et al. 1994... 

Polyethers are usually found in both the filtrate and the mycelial fraction, but in high yielding fermentations they are mosdy in the mycelium because of their low water-solubiUty (162). The high lipophilicity of both the free acid and the salt forms of the polyether antibiotics lends these compounds to efficient organic solvent extraction and chromatography (qv) on adsorbents such as siUca gel and alumina. Many of the production procedures utilize the separation of the mycelium followed by extraction using solvents such as methanol or acetone. A number of the polyethers can be readily crystallized, either as the free acid or as the sodium or potassium salt, after only minimal purification. 

TABLE 13-22 Comparison of Candidate Solvents for Methanol/Acetone Extractive Distillation... 

To extract and evalnate the color pigments from cochineals Dactylopius coccus Costa), a simple method was developed. The procednre is based on the solvent extraction of insect samples nsing methanol and water (65 35, v/v) and a two-level factorial design to optimize the solvent extraction parameters temperature, time, methanol concentration in mixtnre, and yield. For hydrophilic colorants that are more sensitive to temperatnre, water is the solvent of choice. For example, de-aerated water extraction at low temperatnre was applied to separate yellow saffrole and carthamine from saffron (Carthamus tinctorius) florets that contain about 1% yellow saffrole and 0.3% red carthamine. ... 

The oleoresin is obtained from turmeric powder by solvent extraction. Solvents approved for use by European Commission are ethylacetate, acetone, carbon dioxide, dichloromethane, n-butanol, methanol, ethanol, and hexane. The U.S. Food and Drug Administration (FDA) also authorized the use of mixtures of solvents that include those mentioned earlier plus isopropanol and trichloroethylene. After filtration the solvents must be completely removed from the oleoresin. 

Results. Various solvent mixtures were tested for extraction efficiency. The test sample was a bone-dry sediment reference material containing 24.6 ppm of Arochlor 1242. This reference material is a real sediment from New Bedford Harbor which was homogenized and carefully assayed for PCB s by the Cincinnati EPA facility. Figure 3 shows recovery of 1242 using (1) hexane alone, (2) hexane and water (1 1), (3) hexane, water, and ethyl ether, (4) ethyl ether and water, (5) ethyl ether, water, and methanol, (6) methanol and hexane (1 1), and (7) water, methanol, and hexane (1 4 5). This last combination appears to give the best recovery. When added in this order to a dry sample, the effect of the water is to wet the sample, thus permitting extraction by methanol. The extracted PCB is partitioned almost exclusively into the hexane from the aqueous methanol. Final recovery is calculated from initial weight and hexane volume. 

Residues of isoxaflutole, RPA 202248 and RPA 203328 are extracted from surface water or groundwater on to an RP-102 resin solid-phase extraction (SPE) cartridge, then eluted with an acetonitrile-methanol solvent mixture. Residues are determined by liquid chromatography/tandem mass spectrometry (LC/MS/MS) on a Cg column. Quantitation of results is based on a comparison of the ratio of analyte response to isotopically labeled internal standard response versus analyte response to internal standard response for calibration standards. 

Organic solvent extraction. Two analytical methods for acetamiprid have been developed One method is for the parent only and the other determines the total residue of the parent and its metabolites (lM-1-2, lM-1-4 and lC-0). Air-dried soil (20-g equivalent dry soil) is weighed into a centrifuge tube and imidacloprid residue is extracted with 100 mL of methanol-0.1M ammonium chloride (4 1, v/v) using a mechanical shaker for about 30 min. After shaking, the tube is centrifuged at 8000 rpm for 2 min. The supernatant is filtered and the analysis of the soil residue is carried out in the same manner as described above for the parent compound. 

Solvent extraction and addition of a doping reagent (2% lithium chloride in methanol)... 

Solvent extraction of the total lipid extracts from ceramic sherds and charred surface residues Isolation of DAGs and TAGs on silica solid phase cartridges Formation of lithiated adducts from the TAG fraction by addition of 2% lithium chloride in methanol... 

Saponification (see Section 7.4) is carried out to extract more recalcitrant lipids, and the yields are higher than for conventional solvent extraction (Stern et al. 2000). 3 ml of 0.5 M methanolic NaOH is added to 0.1 g of the shard powder and heated at 70°C for 3 hours in a sealed glass vial. After cooling, the supernatant is acidified with HC1 and extracted with three aliquots of 3 ml //-hexane. The hexane will not mix with the methanolic solution (unlike the DCM MeOH used above), but will absorb the lipids and can be transferred into a new clean vial. The removal of excess hexane is carried out as above. Saponification will hydrolyze and methylate any ester functionalities, which removes the requirement to derivatize the samples (Section 7.4) unless other molecules are suspected of being present. However, any wax esters or triacylglycerols will also be hydrolyzed to their fatty acid methyl esters and alcohols therefore, if information on their composition is required, then conventional solvent extraction is recommended as a first step. For subsequent characterization of the lipid extract, see Chapter 7. 

Askari et al. [15] have compared purge and trap, methanol immersion and hot solvent extraction methods for the determination of volatile organic compound in aged soil. These workers found that hot solvent extraction is much more effective than the US Environmental Protection Agency approved purge and trap technique [7, 8]. 

Heise and Litz [26] investigated the extraction behaviour of surfactants (LAS, NPEO and cationics) from sand comparing Soxhlet extraction, accelerated solvent extraction (ASE) and microwave-assisted extraction. Fractionation of the three surfactant types anionic, non-ionic and cationic, was accomplished by column chromatography with aluminium oxide. Soxhlet extraction and ASE of spiked sand with methanol—stored during 7 days prior to extraction—gave similar recoveries for both LAS and NPEO with values between 88 and 116%. Less efficient extraction was achieved by microwave extraction (79% for NPEO). 

Lipids can be extracted from biological samples using a variety of organic solvents. A chloroform-methanol solvent is suitable for all lipids but it is possible to extract different classes of lipid selectively on the basis of their solubility in different organic solvents. This may be achieved by the addition of a solvent that will effect either the precipitation or the extraction of the lipids of interest. An example of the former is the precipitation of high concentrations of phospholipids with cold, dry acetone, and of the latter, the extraction of fatty acids into ether or heptane at an acid pH. However, like all solvent extraction procedures these are not entirely specific. 

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