Polar methylene chloride-soluble

Polar methylene chloride-soluble residues. Polar methylene chloride-soluble residues were found In most of the plant tissues treated with [ C]PCNB (Figure 14). These products were only Identified In peanut IT). The polar methylene chloride-soluble metabolites from peanut, S-(PCP)Cys, S-(PCP)ThloAcetate, and S-(PCP)ThloLactate, were probably produced from S-(PCP)GSH by the pathway shown In Figure 15. Intact peanut plants treated with S-[( C)PCP]Cys and harvested 20 days later yielded S-(( C)-PCP]ThloAcetate In T.3% yield however, S-(( C)PCP]ThloLactate was not detected. An S-substltuted 2-thloacetlc acid metabolite has also been reported In the metabolism of EPTC In the rat ( 1 ). 

Methylene chloride-soluble residues. Methylene chloride-or chloroform-soluble C-labeled products were major residues in all of the plant tissues examined except peanut cell ciiltures (Figure 3). Chloroform-soluble C accounted for 59.2 of the radioactivity isolated from peanut roots 48 hr after treatment with [ C]PCNB. The radioactivity was in the form of PCNB (28.7 ), pentachloroaniline (22.5 ), pentachlorothiophenol (2.6 ) pentachlorothloanlsole (3.1 ) pentachlorothloanlsole sulfoxide (0.5 ) S-(pentachlorophenyl)-2-thioaoetic acid [(S-(PCP)ThioAcetate] (0.5 ) and S-(pentachlorophenyl)-3-thio-2-hydroxypropionic acid [S-(PCP)ThioLactate] (0.2 ) and S-(PCP)Cys (trace) (J), The structures of these compounds are shown in Figure 13. Based on TLC, the last three compounds in this list were classified as polar chloroform- or methylene chloride-soluble residues and the remaining compounds were classified as nonpolar residues. 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

The second approach was taken by practicing liquid chromatographers. They routinely dealt with thermally labile, highly polar molecules and frequently sacrificed resolution, and speed in their separations because of the aqueous mobile phases that were required. With the enhanced diffusion and decreased viscosity of supercritical fluids over liquids, chromatographic run-time and resolution could be improved when supercritical fluids were used. But solubility in pure carbon dioxide mobile phases, which has the solvating powers from hexane to methylene chloride under normal density ranges, was a problem for these polar molecules. To compensate for this, experimentalists started working with mixed mobile phases. These mixed phases were based on... 

Methylene chloride This solvent is a slightly polar solvent also known as dichloromethane, CH2C12. Its solubility in water is 1.32 g/100 mL. It is denser than water (density = 1.33 g/mL) thus it would be the bottom layer when used with a water solution in a separatory funnel. It may form an emulsion when shaken in a separatory funnel with water solutions. It is not flammable and is considered to have a low toxicity level. 

FIGURE 3 2 Solvent extraction efficiencies (EF) as functions of dielectric constants (D), solubility parameters (6), and polarity parameters (P and E -). Solvents studied silicon tetrachloride, carbon disulfide, n pentane. Freon 113, cyclopentane, n-hexane, carbon tetradiloride, diethylether, cyclohexane, isooctane, benzene (reference, EF 100), toluene, trichloroethylene, diethylamine, chloroform, triethylamine, methylene, chloride, tetra-hydrofuran, l,4 dioxane, pyridine, 2 propanol, acetone, ethanol, methanol, dimethyl sulfoxide, and water. Reprinted with permission from Grosjean. ... 

The effect of the moisture level in the eluent on the retention behavior is most pronounced with the least polar solvents, such as the hydrocarbons, in which water has a very limited solubility, usually less than 100 ppm. Conversely, the greater the solubility of water in the organic solvent is, the smaller the effect. For example, the water content of methylene chloride may vary by several parts per million without appreciably changing the k values as the solubility of water in CHtCIt is about 0.2%. 

Specific examples illustrate that similar principles affect the absorption spectra. For example, as we have pointed out above, the neutral form of the C-2 benzyl ester is red in MeOH and orange in methylene chloride. Thus it has the spectrum of the ionized form in the polar, protic solvent and of the nonionized form in the nonpolar solvent methylene chloride [248]. The tributyl ammonium salt of the C-2 octyl ester is soluble in solvents ranging from ethanol-water to toluene. Its spectrum in an essentially nonionizing solvent such as toluene is that of the ionized xanthene [249], The spectrum of the pyrillium salt in ethanol is concentration dependent. In dilute solution the compound is totally ionized and is red, whereas in concentrated solution the compound is not fully ionized and the orange form predominates, as predicted by the law of mass action. 

Effects of Substitution on Spectra Solvent Effects. Solvent effects on the absorption spectra can be summarized as follows if the compound is soluble in water, alcohols, and polar, protic solvents such as DMSO, DME, and DMF, the /.max is most red shifted in polar, nonprotic solvents. Compounds that are soluble in nonpolar solvents such as CH2C12 are generally not soluble in water, and their absorption lies at about the same place in both alcohols and methylene chloride, but is shifted to the red in polar, nonprotic solvents. The value of Amax also reflects the hydrogen bonding ability of the... 

From Hildebrand s solubility parameter, heptane is less polar than toluene, which in turn is less polar than methylene chloride, etc., to water, the most polar. Unfortunately, toluene and ethyl acetate exhibit similar 8 which does not account for their chemical properties moreover, Hildebrand s solubility parameters are not known for mixtures. 

Extraction of nonpolar compounds using equal volumes of sample and the Folsch mixture (2 1, chloroform/MeOH) gives a very broad polarity cut. Everything from steroids to triglycerides is pulled down into the bottom chloroform-rich layer. Extraction with methylene chloride from a sample acidified with sulfuric acid is more specific, pulling in steroids, fat-soluble vitamins, and free fatty acids. The triglyceride fraction can be extracted using i-PrOH/ hexane (1 9) with little emulsification. 

Although PPE is the most efficient and inexpensive extraction technique, it is also the most nonspecific extraction procedure which is known to be susceptible to matrix effect for LC-MS/MS assay. In contrast, LLE provides a much cleaner extract. LLE, also known as solvent extraction and partitioning, separates analytes based on their relative solubility in two different immiscible solvents, usually water and an organic solvent. The most commonly used solvents for LLE are ethyl acetate (EtOAc), methyl ferf-butyl-ether (MtBE), methylene chloride (CH2C12), and hexane or the combination of the above solvents. In order to manipulate the polarity of the analytes, often a volatile acid or base such as FA or NH4OH respectively at 5-10 %... 

Besides showing the usefulness of the solubility parameter for the quantification of polarity, table 2.2 also illustrates the shortcomings of the model. On the basis of its solubility parameter alone, methylene chloride will be expected to behave quite similar to dioxane, and toluene similar to ethyl acetate. However, in both cases there are considerable differences between the solvents in practice. For example, dioxane is miscible with water in all proportions, while methylene chloride is virtually insoluble in water. Clearly, to account for differences in behaviour between compounds of similar polarity a refinement of the model is needed. 

Some of the salts were isolated in pure crystalline form and showed fairly high thermal stability, but many of the cations were observed only in solution. In certain cases, however, solid complexes are readily formed, like Me3NiMe3Si0S02CF3, although at ambient temperature in solution only unchanged reactants are observed (78). They are often easily soluble in aprotic solvents of high or moderate polarity like acetonitrile and methylene chloride. Some of these complexes are unstable at room temperature, decomposing reversibly to components, and may be observed only at a low temperature (78,242,252,255,256). Sometimes irreversible decomposition to other products takes place. An example is shown in Eq. (48). The majority of these complexes are hydrolytically very unstable... 

The complexes (l,5-cyclooctadiene)(2,4-pentanedionato)-palladium(II) and platinum(II) tetrafluoroborate are air-stable solids, soluble in polar organic solvents such as chloroform, methylene chloride, acetonitrile, acetone, or methanol but insoluble in nonpolar solvents such as alkanes, benzene, or ether. Their solutions in acetone have conductivities typical of 1 1 electrolytes. Their proton magnetic resonance spectra (in CDC13 solutions, internal tetramethylsilane reference at 60 MHz.) show peaks due to coordinated cyclooctadiene at 3.78 and 6.7-7.4r (Pd) and at 4.25 and 6.9-7.6r (Pt) and due to the chelated /3-diketone at 4.39 and 7.88r (Pd) and at 4.15 and 7.81r (Pt) with the expected area ratios. In the spectrum of the platinum compound coupling with the 95Pt isotope (33 %... 

Solubility has not been analytically explored. Solubility has been explored for purification, separation, or complexa-tion. In general, good solvents for CE cryptands are polar organic solvents such as acetone, chloroform, methylene chloride, MeCN, dimethylformamide (DMF), A -methyl-2-pyrrolidone (NMP), ethyl acetate, and alcohols. Table 6 summarizes the column chromatographic conditions used for cryptand purification. 

The HB/MtX -initiated polymerizations of vinyl ethers are typically carried out in nonpolar media such as toluene and n-hexane (depending on the solubility of the products) at temperatures below 0° C. In some cases, however, polar solvents (e.g., methylene chloride) may be used at appropriate initiator/activator mole ratios [119] and, specifically with the HI/ZnI2 system, controlled/living polymerization is feasible even at room temperature ( + 25° C) [98,99]. 

Solubility sol in both polar and nonpolar aprotic solvents like diethyl ether, THF, methylene chloride, pentane, hexane, etc. 

Peptide synthesis. The compound is useful as a coupling agent because the corresponding urea derivative is soluble in dilute acid and hence readily separated from the peptide. Squibb workers found it far superior to DCC for the final cycliza-tion step in the synthesis of a peptide lactone related to the antibiotic vemamycin B methylene chloride was found to be an excellent solvent. The polar character of the urea formed facilitated its separation from the product. Of all other coupling agents tested, only N,N -carbonyldiimidazole and N-ethyl-5-phenylisoxazolium 3 -sulfonate permitted isolation of the cyclized peptide, if in much lower yield. 

Standard procedures were followed for isolation of the toxic principles from mycelium of FA 120. A methylene chloride extract of the freeze-dried hyphae was initially partitioned between hexane and aqueous methanol to separate lipids from more polar material. Bio-assay-monitored chromatographic fractionation of the hexane-soluble material led to the isolation of a fraction (ca. 5% of the hyphal weight) which could account for much of the toxicity of the hyphae of FA 120 to spruce budworm larvae. The spectroscopic and chemical properties of this material were characteristic of the enniatins, a group of cyclic hexadepsipeptide ionophore antibiotics produced by several plant pathogenic Fusarium species, including F. lateritium... 

Carotenes are relatively non-polar compounds which are soluble in lipophilic solvents. Most of the known natural carotenoids are oxygenated compounds, often termed xanthophylls, and may be classified as derivatives of the hydrocarbons lycopene or alpha-, or beta-carotene. Although alpha, beta, and gamma all have vitamin A activity in food products, only beta-carotene is used for calculating the vitamin A in vegetables. Carotenes are readily oxidised by light, air and many of the typical extraction solvents (or solvent impurities) including tetrahydrofuran (THF), chloroform, methylene chloride and hexane. 

After precipitation, neutralization, and drying of the product, it is dissolved in a volatile organic solvent and dry spun. The diacetate is soluble in acetone, but the less polar triacetate requires a solvent such a methylene chloride. 

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