Base extraction effects

Eyal, A.M. Canari, R. pH dependence of carboxylic and mineral acid extraction by amine-based extractants Effects of pKa, amine basicity, and diluent properties, Ind. Eng. Chem. Res. 34 (1995) 1789-1798. 

A number of antioxidants have been accepted by the FDA as indirect additives for polymers used in food appHcations. Acceptance is deterrnined by subchronic or chronic toxicity in more than one animal species and by the concentration expected in the diet, based on the amount of the additive extracted from the polymer by typical foods or solvents that simulate food in their extractive effects. Only materials of insignificant risk to the consumer are regulated by the FDA for use in plastics contacted by food stuffs. 

Malien-Aubert, C., Dangles, O., and Amiot, M.J., Color stability of commercial anthocyanin-based extracts in relation to phenolic composition protective effects by intra- and intermolecular copigmentation, J. Agric. Food Chem., 49, 170, 2001. 

The above-mentioned results indicate the additive effect of protons. Actually, a catalytic process is formed by protonation of the metal-oxygen bond instead of silylation. 2,6-Lutidine hydrochloride or 2,4,6-collidine hydrochloride serves as a proton source in the Cp2TiCl2-catalyzed pinacol coupling of aromatic aldehydes in the presence of Mn as the stoichiometric reduc-tant [30]. Considering the pKa values, pyridinium hydrochlorides are likely to be an appropriate proton source. Protonation of the titanium-bound oxygen atom permits regeneration of the active catalyst. High diastereoselectivity is attained by this fast protonation. Furthermore, pyridine derivatives can be recovered simply by acid-base extraction or distillation. 

Due to the effect of plant roots and the natural or normal decomposition of soil minerals, some phosphate and other nutrients will become available [7] during the growing season and thus must be accounted for. The soluble and exchangeable phosphate (i.e., the immediately available phosphate) and that portion of the soil phosphate that will become available to plants during the growing season are determined by the Olson extractant. A typical base extraction of soil nutrients is given in Procedure 11.7 ... 

Since parasorbic acid was previously isolated by steam distillation of the juice of mountain ash berries (.S), we steam distilled a sample of the cranberry leaf extract, but obtained little 2. The literature reports that before the ash berry juice was distilled, it was treated with calcium hydroxide to precipitate malic acid. Tschesche later showed that such treatment followed by acidification converted the glucoside of parasorbic acid, into the free acid (lactone), 2, (9). This base treatment effects a B-ellmination of the glucose fragment. In the absence of this base treatment, no free parasorbic acid was liberated from the berries. 

While the properties of polyurethane as an extractant are useful, several problems make it less than ideal. Polyurethanes are far more specific than activated charcoal in removing contaminants. Charcoal separates particles by size, and while it has some specificity, it is well suited for mixtures of diverse chemistries (PAHs vs. halogenated hydrocarbons). Polyurethanes, however, operate on the principle that like dissolves like. They consist of hydrophobic isocyanates and hydrophobic polyalcohols. Thus, the molecules are hydrophobic. The polyalcohol backbone has some polarity, but it is hindered and therefore has a low net polarity. Inasmuch as the extraction effect is based, at least in part, on polarity, polyurethanes are most effective for nonpolar pollutants... 

The effect on reactive compounds and potential alteration of mutagenic activity of the acid-base extraction procedure were major concerns. The TLC method was not recommended because of possible mutagen loss due to reactions on the plate. The Florisil and low-pressure chromatographic methods were considered to be research methods. 

Figure 1A. Effect of base extraction on GC capillary chromatographic profiles.

The same statistical procedures were used here to evaluate the effects of humics on batch and continuous LLE. A base extraction procedure (19) was required for processing methylene chloride extracts prior to GC injection in order to protect the GC column from contamination by humics. This process led to losses of 2,4-dichlorophenol and the chlorinated biphenyls. Therefore, these compounds were not used in the evaluation of the CLLE in the presence of humics. All other compounds were not affected by the base extraction procedure. The ANOV procedure tested each compound for changes in concentration by comparing early batch extraction recoveries (from freshly prepared solution) to later ones (after the 12.5-L extraction). This process was done separately for Parts 1 and 2. It was therefore possible to test each compound for time-dependent decreasing concentration with and without the presence of humics. 

Oxidation of the crude product mixtures containing both regioisomers 44 and 45 gave Cbz-protected amino acid 46 and amino ketone 47, which could then be separated by simple acid-base-extraction. As oxidizing reagents, periodic acid and a catalytic amount of ruthenium trichloride were found to be suitable. For some cases in which chemical yields were low, a TEMPO-catalyzed oxidation with bleach as oxidant was more effective. 

The one-phase liquid system is more frequently encountered since many organic reactions are carried out in solution. Direct fractional distillation may separate the product, if it is a liquid, from the solvent and other liquid reagents, or concentration or cooling may lead to direct crystallisation of the product if this is a solid. However, it is often more appropriate, whether the required product is a liquid or solid, to subject the solution to the acid/base extraction procedure outlined above and considered in detail on p. 162. This acid/base extraction procedure can be done directly if the product is in solution in a water-immiscible solvent. A knowledge of the acid-base nature of the product and of its water solubility is necessary to ensure that the appropriate fraction is retained for product recovery. In those cases where the reaction solvent is water miscible (e.g. methanol, ethanol, dimethylsulphoxide, etc.) it is necessary to remove all or most of the solvent by distillation and to dissolve the residue in an excess of a water-immiscible solvent before commencing the extraction procedure. The removal of solvent from fractions obtained by these extraction procedures is these days readily effected by the use of a rotary evaporator (p. 185) and this obviates the tedium of removal of large volumes of solvent by conventional distillation. 

Racemization and Recycle of the n-Butanol Mother Liquors from the DBTA Resolution. The aqueous base extraction of DBTA followed by acidification of the aqueous layer and filtration of the DBTA proved relatively straight forward. On the other hand, much work was needed to identify and develop the most cost-effective system for racemizing the SR/RR mixture (approximately 70 30 respectively in composition) and to recycle the racemate produced. 

In a different type of experiment, Cai et al. [63] measured the induction of SB induced by electrons of 8-68 eV in SAM of oligonucleotides. From their results they extracted effective cross sections and AL for SB. A 50-base long thiolated oligonucleotide (OligoS), 5,-(GCTA)12GC(CH2)3-SS-(CH2)3-OH-3, was labelled at the 5 -end with 32P and chemisorbed at 3 -sulfur(S) end onto a gold... 

Hence an addic pH will optimise the extraction of an acid into organic solvent and a basic pH will optimise the extraction of a base. This effect is known as ion suppression. 

The potential of ultrasonic extraction for field-based extractions has been put into use in the industrial hygiene and environmental single-element analysis of, for example, lead from glass fibre filter ambient air samples [13,14] or from lead-based paint, urban dust and river sediment [15] hexavalent chromium from coal fly ash and paint chips [16] and strontium from river sediment [17]. Ultrasonic extraction has also proved effective as a prior step in multi-element determinations of heavy metals. 

The importance of the acidic and steric properties of mono-acidic phosphorus-based extractants in the extraction of metals has been well established. The work of Mason, Peppard, et al. (2, 3) has shown that combined acidic and steric effects which result from altering the structure of the acidic extractants may be varied to give a wide range of extraction constants (Ks) for specific metals. Ks = K[H+]a/F, where Ks is a constant characteristic of the system, K is the distribution ratio, H is the hydrogen ion concentration in the equilibrated aqueous phase, F is the concentration of extractant in the equilibrated organic phase, a and b are the respective hydrogen ion and extractant dependencies. Recent studies, to be published, involving the... 

Although many of the procedures listed in Table 11.9 are used for contaminated soils, they will not necessarily measure plant-available contents but rather, the labile or mobile species contents. They can best be indicated as potentially plant-available contents rather than actual contents. The most commonly used extractants are diethylenetriaminepentaacetic acid-triethanolamine (DTPA-TEA), buffered at pH 7.3 (Lindsay and Norvell, 1978) and 0.05 M CaCh (Sauerbeck and Styperek, 1984). Some authors also reported no relationship between extractable metals and test plant metal concentrations (e.g., Haq and Miller, 1972 Rappaport et al., 1988). O Connor (1988) has subsequently identified an entire series of misuses of the DTPA test, which probably account for failure of the test,. Two major constraints with the DTPA extractant include the high pH (that may not typify soil pH) and chelation effect of the ligand ion. The chelate-based extractants tend to extract significantly higher amounts of trace elements and thus may not necessarily reflect the plant-available content in soils. To compensate for the high pH of the extractant, O Connor (1988) suggested inclusion of pH as one of the variables in the correlation studies. 

Sun XQ, Peng B, Ji Y et al (2008) An effective method for enhancing metal-ions selectivity of ionic liquid-based extraction system adding water-soluble complexing agent. Talanta 74(4) 1071-1074... 

The work reported here has provided valuable lessons. For example, inclusion of high salt levels in the initial enrichment phase can be deleterious both to antibody binding and lysis of non-target organisms (penicillin-based antibiotics only lyse growing cells), and lysostaphin is not totally specific, but is cost effective and does not inhibit AK as detergent-based extractants can. 

This is defined as a reaction which effects a structural change and gives an isolable product, but which may or may not be isolated in practice. (This includes salt formations where isolated, but not transient formations in acid/base extractions). When making route comparisons, a higher number of steps would imply that more complex chemistry is being used to reach the target. 

MALIEN-AUBERT c, DANGLES o and AMIOT M J (2001), Color Stability of commercial anthocyanin-based extracts in relation to the phenolic composition. Protective effects by into and intermolecular copigmentation , J Agric Food Chem, 49, 170-176. 

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