Partition hexane-water

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. 

A gas liquid chromatographic (GLC) method was described for determining residues of Bayer 73 (2-aminoethanol salt of niclosamide) in fish muscle, aquatic invertebrates, mud, and water by analyzing for 2-chloro-4-nitroaniline, a hydrolysis product of Bayer 73 [83]. Residues were extracted with acetone-formic acid (98 + 2), and partitioned from water samples with chloroform. After sample cleanup by solvent and acid base partitioning, the concentrated extract was hydrolyzed with 2N NaOH and H202 for 10 min at 95°C. The 2-chloro-4-nitroaniline was then partitioned hexane ethyl ether (7 + 3) and determined by electron capture GLC. Average recoveries were 88% for fish, 82% for invertebrates, 82% for mud, and 98% for water at 3 or more fortification levels. 

The octanol-water partition coefficient appears to correlate better with biological activity than partition coefficients in other solvent-water mixtures as, for example, hexane water, because the amphiphilic nature of octanol can accommodate a greater variety of more or less hydrophobic molecules. 

C. (Z)-[2-(Fluoromethylene)cyclohexyl]benzene (3). To a solution of (fluorovinyl)stannane 2 (26.0 g, 0.054 mol) in dry THF (150 mL) is added 65 mL of 1 M sodium methoxide in methanol (prepared by the addition of 1.50 g (0.065 g-atom) of sodium to 65 mL of methanol). The solution is refluxed for 18 hr under nitrogen (Note 14), cooled to ambient temperature and concentrated on a rotary evaporator. The residue is partitioned between water (200 mL) and hexane (200 mL). The aqueous layer is separated and extracted with hexane (100 mL). The combined organic layers are dried (magnesium sulfate) and concentrated on a rotary evaporator to give a colorless oil (30 g). Kugelrohr distillation gives 10.0-10.2 g (97-100%) of fluoro olefin 3 (bp 85-90°C, 0.4 mm) as a colorless oil (Note 15). 

Hexane represents the aliphatic group. Most of the aliphatic compounds are branched, bnt the same trend of low solubility that decreases with increasing C nnmber is typical of all snbstances in this gronp. Due to their very low solubility, these compounds hardly partition to water and migrate mainly as vapors, as a separate phase, or adsorbed on particnlate matter. In very high concentrations (thousands of ppm), hexane is a lethal narcotic to humans (HCN 2005). High-level exposnre affects several enzyme fnnctions, which lead to increased liver weight. No data on octane toxicity are available, and it is considered nontoxic. 

The iridoids, plumericin, isoplumericin, plumieride and fulvoplumierin, were present in the extracts of Plumeria rubra bark. After maceration of the powdered bark (3.5 kg) with dichloro-methane/methanol (1 1) and pure methanol, the combined extracts were partitioned between water and ethyl acetate. To isolate the four iridoids, the organic layer was chromatographed twice in a column using silica gel and gradient of increasing polarity with hexane and ethyl acetate, ethyl acetate and methanol, and then pure methanol. The amounts of the compounds isolated were not reported [75]. 

The aldehyde (475 mg, 0.9 mmol) was dissolved in MeOH (100 mL), and NaCN (220.5 mg, 4.5 mmol) was added. Oxidation was carried out over 2 days. Then the reaction mixture was filtered through Celite, and the filtrate was concentrated in vacuo. The oily residue was partitioned between water (50 mL) and EtjO (150 mL). The organic layer was washed with brine (50 mL), dried (MgSO ), and concentrated in vacuo. Flash chromatography (hexanes-EtOAc, 7 3) afforded the product 59 (393 mg, 70%) as an oil [a]D + 2.5° (c 1, CHClj). 

Each monomer is ascribed with a two-dimensional coordinate, of which the abscissa dimension corresponds to the affinity to the polar (water) or the nonpolar phase (hexane) and the ordinate dimension corresponds to interfacial activity. The standard free energy of partition between water and hexane is used as a quantitative parameter for the abscissa axis (AFpart), whereas the standard energy of adsorption at the interface is used for the ordinate axis (AFa(js). Both parameters are normalized by the kT factor. The normalized values are denoted as A/part and A/ads, respectively. Thus,... 

The first attempt to resolve this problem involved the use of Alog P between two partition systems, namely octanol-water and hexane-water, as a model for the penetration of the blood-brain barrier [29]. This leads back to Seiler s fH value [20] (for details see Section 4.2). 

Safari et al. (1993) examined the interesterification of milk fat by the lipase from Rhizomucor miehei in various organic solvents (hexane, hexane-choloroform (70 30, v/v), and hexane-ethylacetate (70 30, v/v)). The addition of chloroform or ethyl acetate to hexane increased lipase activity. It was suggested that the polarity of the solvent influences the partitioning of water in the system with consequent effects on enzymic activity. Bornaz et al. 

To 100 ml N-methyl pyrrolidine containing K2CO3 (32.5 mmol) was added 2-bromothiophenol (32.5 mmol) and 4-fluoro-3-trifluoro-methylbenzaldehyde (26 mmol) and the mixture heated to 85 °C 12 hours. The mixture was cooled, partitioned between water and diethyl ether, the organic layer washed twice with brine, dried and the product isolated by chromatography using silica gel with hexane/EtOAc, 4 1, in 93% yield. 

To the product from Step 2 (5.3 mmol) dissolved in 5 ml DMSO was added l-(4-hydroxyphenyl)imidazole (5.8 mmol) and CS2CO3 (5.6mmol) and the mixture heated to 90 °C 18 hours. The reaction mixture was partitioned between water and EtOAc, concentrated, purified by chromatography on silica gel using EtOAc/hexanes, and the product isolated. 

Water affects the reaction rate through its effect on reaction kinetics and protein hydration, which is required for optimal enzyme conformation and activity. Enzymes need a small amount of water to maintain their activity however, increasing the water content can decrease the reaction rate as a result of hydrophilic hin-drance/barrier to the hydrophobic substrate, or because of denaturation of the enzyme (189). These opposite effects result in an optimum water content for each enzyme. In SCFs, both the water content of the enzyme support and water solubilized in the supercritical phase determine the enzyme activity. Water content of the enzyme support is, in turn, determined by the distribution/partition of water between the enzyme and solvent, which can be estimated from water adsorption isotherms (141, 152). The solubility of water in the supercritical phase, operating conditions, and composition of the system (i.e., ethanol content) can affect the water distribution and, hence, determine the total amount of water that needs to be introduced into the system to attain the optimum water content of the support. The optimum water content of the enzyme is not affected by the reaction media, as demonstrated by Marty et al. (152), for esterification reaction using immobilized lipase in n-hexane and SCC02- Enzyme activity in different solvents should, thus, be compared at similar water content of the enzyme support. 

Some relation has been found between the rate of sorption by poly (vinyl chloride) (PVC) bags of a series of dmgs and their hexane/ water partition coefficients.Table 5.20 shows the data for sorption of 100 cm PVC infusion bags (equivalent to 11 g of PVC). In the table,... 

Ruelle P. The n-octanol and n-hexane/water partition coefficient of environmentally relevant chemicals predicted from the mobile order and disorder (MOD) thermodynamics. Chemosphere 2000 40 457-512. 

In brief, this involved spiking homogenized tissues with non-radiolabeled reference compounds, methanol extraction, hexane-water partitioning followed by reverse phase chromatography (XAD-2 and C-18 HPLC). The activity in each fraction was quantified by liquid scintillation counting. 

Includes C-activity in the hexane phase after hexane water partition and all " C-activity eluted from HPLC (C-18 column) after N -acetylsulfamethazine. 

The single constant Wilson equation was fitted to experimental partition coefficient data for ethanol for the ternary systems benzene-water-ethanol (9) and n-hexane-water-ethanol (12). The partition coefficient was calculated from equation (12) using the Wilson equation to compute the activity coefficients. The constants, Xy, were chosen to give a best fit in the least squares. sense to the experimental partition coefficients. Table II shows the resulting constants. 

The constants were then used to predict partition coefficients for the four component benzene-hexane-water-ethanol system. This prediction was accomplished in the following way. The hydrocarbon phase composition was assumed to be known. The activity coeifficient yes was calculated by the Wilson equation. Equation (10) was then solved simultaneously with the partition coefficient equation ... 

Brassinosteroids are extracted preferably by methanol or meihanol/ethylacetate, partitioned between water and chloroform as well as 80% methanol and n-hexane. The purification is carried out by successive chromatographic methods such as silica gel column chromatography, Sephadex LH-20 chromatography, ion exchange chromatography and preparative HPLC. Concerning the... 

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