Extraction, solvent salts

In France, Compagnie Europnene du Zirconium (CEZUS) now owned jointly by Pechiney, Eramatome, and Cogema, uses a separation (14) based on the extractive distillation of zirconium—hafnium tetrachlorides in a molten potassium chloride—aluminum trichloride solvent at atmospheric pressure at 350°C. Eor feed, the impure zirconium—hafnium tetrachlorides from the zircon chlorination are first purified by sublimation. The purified tetrachlorides are again sublimed to vapor feed the distillation column containing the solvent salt. Hafnium tetrachloride is recovered in an enriched overhead fraction which is accumulated and reprocessed to pure hafnium tetrachloride. 

In general, the tetracyclines are yellow crystalline compounds that have amphoteric properties (Fig. 2) (15). They are soluble in both aqueous acid and aqueous base. The acid salts tend to be soluble in organic solvents such as 1-butanol, dioxane, and 2-ethoxyethanol In fact, 1-butanol is used to extract the salts from aqueous solution. 

A co-solvent that is poorly miscible with ionic liquids but highly miscible with the products can be added in the separation step (after the reaction) to facilitate the product separation. The Pd-mediated FFeck coupling of aryl halides or benzoic anhydride with alkenes, for example, can be performed in [BMIM][PFg], the products being extracted with cyclohexane. In this case, water can also be used as an extraction solvent, to remove the salt by-products formed in the reaction [18]. From a practical point of view, the addition of a co-solvent can result in cross-contamination, and it has to be separated from the products in a supplementary step (distillation). More interestingly, unreacted organic reactants themselves (if they have nonpolar character) can be recycled to the separation step and can be used as the extractant co-solvent. 

Those in which solvent molecules are directly involved in formation of the ion association complex. Most of the solvents (ethers, esters, ketones and alcohols) which participate in this way contain donor oxygen atoms and the coordinating ability of the solvent is of vital significance. The coordinated solvent molecules facilitate the solvent extraction of salts such as chlorides and nitrates by contributing both to the size of the cation and the resemblance of the complex to the solvent. 

Several extractions are required when the distribution constant is small. The addition -of salts, pH adjustment, ion-pairing reagents, etc., can be used to isprove the distribution of organic solutes into the extracting solvent. 

Protein precipitation is used routinely in bioanalytical laboratories in the pharmaceutical industry. Plasma is mixed with an excess (3 to 5 times) of organic solvent (typically acetonitrile or methanol) or an acid such as formic acid. The proteins precipitate out of solution, the sample is centrifuged, and the supernatant is analyzed. While this method is relatively fast and simple, the extract contains salts and lipids that can interfere with subsequent analyses. Often, a second technique such as SPE is used for further cleanup. Table 2.4 exhibits various samples that... 

Alternatively, direct methods (syringe infusion, flow injection) can be used as a preliminary step in determining the optimal MS detector conditions for particular molecules. This is especially useful when the MS is attached to a liquid chromatograph, in which the fluid entering the MS will vary with gradient elutions (varied solvent and salt compositions) or with sample types (varied sample matrices, extraction solvents, included salts, etc.), which can affect the predominant ion type and sensitivity, or produce other matrix effects such as ion suppression or extraneous signals. 

The pesticide industry generates many concentrated wastes that are considered hazardous wastes. These wastes must be detoxified, pretreated, or disposed of safely in approved facilities. Incineration is a common waste destruction method. Deep well injection is a common disposal method. Other technologies such as wet air oxidation, solvent extraction, molten-salt combustion, and microwave plasma destmction have been investigated for pesticide waste applications. 

Other potential technologies that can be applied to the treatment of concentrated wastes from pesticide manufacturing include wet air oxidation, solvent extraction, molten salt combustion, and microwave plasma destmction. 

Methylene chloride is exchanged for diethyl ether, since removal of the zinc salts formed as reaction by-products is facilitated by use of an extraction solvent that is less dense than water. 

This procedure is often used when the extraction solvent chosen has been water alone, since in this case polar compounds such as salts and amino acids may contaminate the extract. Precipitation with an appropriate solvent, e.g., a mixture of acetate buffer/acetonitrile (22), is then required. Water-soluble macromolecules also interfere and may be removed to a considerable extent by simple precipitation with an organic solvent, for example, ethanol. Nevertheless this may be troublesome, since a proportion of the carbohydrates of interest may become absorbed to the precipitated material, which will be subsequently lost. On the other hand, the sugars must be sufficiently soluble in the solvent used to avoid its precipitation from the solution. 

All experiments were performed on a Lee Scientific (Dionex Corporation - Lee Scientific Division - Salt Lake City, UT) -602D Supercritical Fluid/Gas Chromatograph equipped with a 0.5 ml extraction cell. SFC grade carbon dioxide (Scott Specialty Gases, Plumsteadville, PA) was used as the extracting solvent and mobile phase in all experiments. All SFE and SFC investigations were performed under isothermal conditions. Flame ionization detection operating at 325°C was used in all studies. The specific column, conditions, and parameters are listed in the Applications section. 

Leaching The dissolution and extraction of chemical species from solid samples by water, acids, bases, organic solvents, salt solutions, or other liquids (compare with batch leaching, column leaching, sequential batch leaching, serial batch leaching, and leaching test). 

Though the lipid phosphoric acids are present in very low concentrations even in stimulated cells, it is possible with certain precautions to isolate them in good yields. Perhaps the most important experimental factor in a successful extraction is the inclusion of acid, usually 1 N HC1, in the extracting solvent. This is important because these acidic compounds normally exist as salts in the cell in order to extract them into a chloroform-rich fraction, for example, they must be converted to the free acid form. Given the satisfactory isolation of the total lipids, aliquots of this fraction can be assayed for total phosphorus by the macro procedure described in Chapter 4 or by the submicrogram method described by Bottcher et al. (1961). Two approaches can be used to separate the lysoPAs and the PAs from the other lipids as outlined on the following section. 

In order to avoid the undesirable isomerization to isopilocarpine (Section III,D,3) and, probably, to avoid enzymatic degradation, the Jaborandi leaves are processed as rapidly as possible. Acidification converts the alkaloids to their water-soluble salts, which allows defatting of the leaves with, for example, petroleum ether. Alkalinization and extraction with a suitable lipid-extracting solvent or solvent mixture gives the crude alkaloid mixture. (+)-Pilocarpine (mp 34°C) crystallizes only with difficulty it can be obtained readily as the nitrate salt (mp 178°C) in the absence of isopilocarpine. The separation of isopilocarpine nitrate from pilocarpine nitrate by crystallization is often difficult because mixtures may give products of constant melting points the same holds for the hydrochlorides. 

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