Extraction experiment

Results are reported in energy units that correspond to those in experimental papers molar units for binding equilibria (kcal/mol) and molecular units for ligand extraction experiments (zj = pN nm). 1 kcal/mol = 6.9 zJ, and at 300 K, ktsT = 4.2 zJ. 

Thus, we have found unexpected complexities and even in this simple system have not yet been unable to accurately extrapolate the results of simulations done over periods varying from 1 to several hundred ps, to the low-friction conditions of extraction experiments performed in times on the oi dc r of ms. The present results indicate that one should not expect agreement between extraction experiments and simulations in more complex situations typically found in experiments, involving also a reverse flow of water molecules to fill the site being evacuated by the ligand, unless the simulation times are prolonged well beyond the scope of current computational resources, and thereby strengthen the conclusion reached in the second theoretical study of extraction of biotin from it.s complex with avidin [19]. 

The instrumentation which until now has been used in chiral extraction experiments is very diverse, ranging from the simple extraction funnel [123, 180], the U-or W-tubes [171, 181], to more sophisticated devices, such as hollow-fiber extraction apparatus [175] or other membrane-assisted systems. Most of these experiments... 

Proteins (BSA or ovomucoid, OVM) have also been successful in the preparative resolution of enantiomers by liquid-liquid extraction, either between aqueous and lipophilic phases [181] or in aqueous two-phase systems (ATPS) [123, 180]. The resolution of d,l-kynurenine [180] and ofloxacin and carvediol [123] were performed using a countercurrent extraction process with eight separatory funnels. The significant number of stages needed for these complete resolutions in the mentioned references and others [123, 180, 189], can be overcome with more efficient techniques. Thus, the resolution of d,l-kynurenine performed by Sellergren et al. in 1988 by extraction experiments was improved with CCC technologies 10 years later [128]. 

Selective extraction experiments were then performed to see transference of some transition elements (Cu ", Ni ", Co ", and Fe " ) from the aqueous phase to the organic phase by the synthesized polymeric calixarenes. Phase-transfer studies in water-chloroform confirmed that polymer 2b and 3b were Fe ion-selective as was its monomer (1). Extraction of Fe " cation with 2b and 3b was observed to be maximum at pH 5.4. Only trace amounts of other metal cations such as Cu, Ni ", and Co " were transferred from the aqueous to the organic phase (Table 3). Furthermore, the extracted quantities of these cations remained unaffected with increasing pH. The effect of pH on the extraction of 3b was lower and 56% extraction was accomplished even at pH 2.2. The extraction experiments were also performed with calix[4]arene (1) the ratio was 8.4% at pH 2.2. The polymeric calix[4]arenes were selective to extract Fe " from an aqueous solution, which contained Cu +, Ni, Co ", and Fe " cations, and it was observed that the... 

These phenomena can be explained by the (hard-soft) acid-base principal as follows C=N-OH is a soft base, hence has stronger affinity towards soft basic metal cations than hard metal cations. The strong participation of the N-OH group in complex formation was further confirmed by the results shown for extraction experiments with 5 and 6. 

Various extraction methods for phenolic compounds in plant material have been published (Ayres and Loike, 1990 Arts and Hollman, 1998 Andreasen et ah, 2000 Fernandez et al., 2000). In this case phenolic compounds were an important part of the plant material and all the published methods were optimised to remove those analytes from the matrix. Our interest was to find the solvents to modily the taste, but not to extract the phenolic compounds of interest. In each test the technical treatment of the sample was similar. Extraction was carried out at room temperature (approximately 23 °C) for 30 minutes in a horizontal shaker with 200 rpm. Samples were weighed into extraction vials and solvent was added. The vials were closed with caps to minimise the evaporation of the extraction solvent. After 30 minutes the samples were filtered to separate the solvent from the solid. Filter papers were placed on aluminium foil and, after the solvent evaporahon, were removed. Extracted samples were dried at 100°C for 30 minutes to evaporate all the solvent traces. The solvents tested were chloroform, ethanol, diethylether, butanol, ethylacetate, heptane, n-hexane and cyclohexane and they were tested with different solvent/solid ratios. Methanol (MeOH) and acetonitrile (ACN) were not considered because of the high solubility of catechins and lignans to MeOH and ACN. The extracted phloem samples were tasted in the same way as the heated ones. Detailed results from each extraction experiment are presented in Table 14.2. 

Mobilization of inicronutrients such as Zn, Mn, Cu, and Co and of heavy metals (Cd, Ni) in soil extraction experiments with root exudates isolated from various axenically grown plants is well documented (61,204-206) and has been related to the presence of complexing agents. 

Solvent extraction experiments were performed on all processed homopolymers and blends. The samples were first weighed then immersed in 20 mL acetone for 24 hours at room temperature. The remaining solid rod was removed from the acetone, vacuum dried and reweighed. The remaining experimentation was performed only on samples from (A) and (D) above. 

TABLE 12. Description of the experiment parameters for the reference experiment and ground water extraction experiment... 

Parameter Reference experiment Ground water extraction experiment... 

The naphthalene extraction experiment was carried out under similar conditions except that nitrogen was used as cover gas instead of deuterium. The spent naphthalene-d8 was separated from the residue by distillation at reduced pressure. The residue was solvent fractionated with tetrahydrofuran (J. T. Baker Chemical Co.). 

The results of the two donor solvent experiments (E10 and E19) are discussed below. The coal extraction experiment (E20) is discussed in a subsequent section. 

The purpose of this experiment was to investigate the extent and the structural specificity of hydrogen exchange during the extraction of bituminous coal with naphthalene. Table I includes the data of an extraction experiment (E20) conducted with naphtha-lene-d8 using nitrogen as the cover gas. In the experiment, the reactants were heated at 380°C for 1 hour at 2200 psi the same apparatus was applied as in E19. After the run, the spent solvent was separated from the coal by distillation, and the coal and solvent were examined for deuterium and protium incorporation. 

The coal residue was separated into a THF-soluble fraction and a THF-insoluble residue. The wt % yields and atom % 2H compositions are given in Table I. The coal residue was 6 wt % soluble in tetrahydrofuran. The soluble fraction had 23 atom % 2H content. Evaluation of the 2H NMR data showed that 85 wt % of this fraction was derived from the coal and that its deuterium content was 10%. The chemically-bonded naphthalene-d8 content of the THF-soluble fraction, estimated from the 2H NMR data, was about 15 wt % or approximately 1 wt % of the coal. The insoluble residue had 6 atom % 2H content. This indicates that the residue contained approximately 1 wt % chemically-bonded naphthalene which was estimated from the difference in the atom % 2H content of the insoluble residue and recovered naphthalene-d8. This gives a total chemically-bonded naphthalene-d8 content of approximately 2 wt %. Similar results were obtained in extraction experiments made with phenanthrene (30), where it was found that 3-7 wt % of the phenanthrene was chemically linked to the coal product. 

DNA array-CGFI data were provided by Sandy DeVries at Dr. Fredric Waldman s Lab at UCSF. RNA extraction experiments were technically performed by Cheng Liu and Kelly Smith. Both studies were supported by NUT grant 1 R33 CA103455. Use of human tissues has been exempted under 45 CFR 46.101 (b) and was approved by the Institutional Review Board (IRB 009071) at USC. 

One of the more important considerations in determining the end use of synthetic graphite is its contamination with metallic components Metals such as iron, vanadium, and especially in nuclear applications, boron are deleterious to the performance of graphite Table 3 presented the extraction yields of NMP-soluble material for three bituminous coals. For these coals, mineral matter and insoluble coal residue were separated from the extract by simple filtration through 1-2 pm filter paper fable 13 lists the high-temperature ash content in the dry coal, and in their corresponding NMP-insoluble and NMP-soluble products. The reduced ash content of the extract is typically between 0.1 to 0.3 wt% using traditional filtration techniques for the small-scaled extraction experiments... 

Between pH values of ca. 6 and 12 aqueous solutions hold very little dissolved beryllium because of the low solubility of Be(OH)2. When the pH is raised above 12, the hydroxide begins to dissolve with the formation of, first, Be(OH)3 and then, at even higher pH values, Be(OH) (52). The presence of these species in strongly alkaline solutions was confirmed by means of solvent extraction experiments (90) and infrared spectroscopy (31). A speciation diagram is shown in Fig. 7, which was constructed using the values of log /33 = 18.8 and log /34 = 18.6 critically selected from Table III. The diagram illustrates clearly the precipitation and dissolution of Be(OH)2. 

A similar strategy has been applied by Mazik and coworkers. The receptor is usually titrated with increasing amounts of the sugar, to evidence binding, to extract the values of the binding constants and to get the stoichiometry of the complexes formed. Reverse titrations and extraction experiments can also be performed. The structures of the receptors described are based on different scaffolds the above mentioned hexasubstituted tripodal benzene moiety and 3,3, 5,5 -tetrasubstituted... 

The distribution coefficient for a given extraction experiment is 98.0. If the concentration in the extracting solvent is 0.0127 M, what is the concentration in the original solvent ... 

Describe what happens in a liquid-liquid extraction experiment. 

In an extraction experiment, it is found that 0.0376 g of an analyte are extracted into 50 mL of solvent from 150 mL of a water sample. If there was orginally 0.192 g of analyte in this volume of the water sample, what is the distribution coefficient What percent of analyte was extracted ... 

N-hexane, benzene, toluene, and diethyl ether are less dense than water, and thus would be the top layer in an extraction experiment. Liquids with a higher density than water would sink to the bottom of the separatory funnel. 

Some caution is required when comparing the association constants obtained from extraction experiments with those measured under anhydrous, homogeneous conditions. Iwachido et al. (1976, 1977) have shown that the extracted cation retains part of its aqueous solvation shell on complexation. In particular, the small univalent cations (Li+, Na+) and bivalent cations give high hydration numbers for their crown-ether complexes. Water molecules completing the co-ordination sphere of the cation have frequently been encountered in the solid state of crown-ether complexes (Bush and Truter, 1970, 1971). The effect of small amounts of water on the equilibria (1) has not been studied yet for crown ethers. However, it has been found that the presence... 

The cation selectivity in extraction experiments is dependent on differences in both the distribution constants KD and the binding constants Klf) in the water-saturated organic solvent (3). The extractability of alkali cations into... 

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