Extraction acid-base-neutral

No sample fractionation procedure is given in the protocol, but several possible techniques were included in the literature review, including acid/base-neutral extraction, solvent fractionation (8), column chromatography, TLC, and HPLC (presented elsewhere in this chapter). 

The concentrated extract is then split. To one portion, 1.0 mL of DMSO is added, and the dichloromethane is removed under a stream of nitrogen. The resulting DMSO solution is used for the direct assay of the extract. If fractionation of the remaining extract is required, the investigator is given the option of using the acid/base-neutral extraction scheme described in step 3 of the nonaqueous liquid protocol or the HPLC technique described in the sample fractionation methods section. 

The second series of methylene chloride extractions was accomplished by the addition of 300 mL of solvent to the aqueous layer, homogenization for 1 min, then pH adjustment to <2 via the addition of 6.0 N hydrochloric acid. Following an additional homogenization for 1 min, the suspension was centrifuged and processed as for the base-neutral extractions. The extrac-... 

Recently, another class of neutral organophosphorus compounds, namely, N,N-dialkyl carbamoyl methyl phosphonate (CMP) (59) and its phosphine oxide analog (CMPO) have received attention due to their ability to extract even trivalent actinides from acidic solutions along with the hexa- and tetravalent actinide ions. These biden-tate phosphorus-based neutral extractants are reported to be stronger extractants as compared to TOPO (59-62). Pu(IV) and U(VI) are extracted as per the following extraction equilibria ... 

Separation Techniques. The complexity of the organic composition of coal-derived liquids, shale oil, and their related effluents presents a formidable challenge to the analytical chemist. Our approach to this problem has been the classical separation technique based on acid-base-neutral polarity of the organic compounds. We further subdivide the neutral fraction into aromatic and non-aromatic fractions using dimethyl-sulfoxide (DMSO) extraction. DMSO effectively removes multiringed aromatic compounds with great eflBciency (85-95%) for these complex mixtures and thus allows a straightforward analysis for polynuclear... 

Sample Source Organic Carbon Content (mg C/L) Acid Extracf (ppm) Total Base/Neutral Extract(ppm) Alumina Column Fractions ... 

The sample was denatured with formic acid and extracted with cyclohexane. The organic extracts were purified 130 on a Power Prep automated sample cleanup system with acidic silica gel, acid/base/neutral silica, and a carbon column. PCBs were eluted using dichloromethane and cyclohexane. The eluates were concentrated using a nitrogen evaporator for analysis by GC-HRMS... 

Acid-base-coupled extractants seem to be very attractive for many industrial applications. They allow recovery of acids from waste streams instead of neutralization. Acid and base consumption is thereby reduced, as is the amount of waste to be disposed of. Being also excellent extractants for metal salts, ABC extractants provide for sequential recovery of acids and their salts from waste streams. The extractant composition can be adjusted so that a single extractant can extract first the acid and then the salt at high efficiency, selectivity, and reversibility. Because of this high reversibility, these components are recovered by back-extraction with water, at concentrations approaching those in the feed stream and in some cases even higher. 

Organics(Base-Neutral Extractable) Organics(Acid Extractable) Organics(Pesticides)... 

The purpose of sample preparation is to isolate analytes from a matrix. Another term used for this operation is "sample cleanup," and the two terms are often used interchangeably. Sample preparation can range from a simple "dilute and dioot," in which a portion of the sample is dissolved in a solvent for subsequent introduction into an instrument to complex acid-base-neutral sequential extractions. In this chapter, we ll explore forensic separations and sample preparations that are lised prior to instrumental analysis, which we delve into in the next chapter... 

In recent years, the quaternary ammonium-functionalized ILs have been investigated widely because of its cheap, low toxicity properties. A kind of ILs was designed and synthesized by tricaprylmethylammonium chloride (Aliquat 336 or A336) and traditional carboxylic acid and phosphoric acid extractant [2]. Because the cation and anion of this kind of ILs are all the functional group for the REEs extraction, we called them bifunctional ionic liquid extractants (Bif-ILEs). Bif-ILEs could be synthesized by acid/base neutralization, and this reaction process was under mild condition, with easier purification and good yield (about 70-80 %). 

Chitosan, a widely used natural biopolymer, has been studied for the adsorption of various metal ions from dilute solutions. Unfortunately, the inherent properties of chitosan, such as hydrophilicity and metal-binding capability, are often insufficient to meet the requirements of a number of applications. To improve these properties, both chemical and physical modifications of chitosan are required. Thus, Aliquat 336-functionalized chitosan as adsorbent was prepared. In fact, the new chitosan adsorbent can also be described as P-SIL containing quaternary ammonium ionic liquid [23]. Unlike the previous reported structure, the Aliquat 336-functionalized chitosan, which was prepared by acid/base neutralization reaction, consists largely of cations and anions (Fig. 5.12). The structure was so flexible that the adsorption ability could be controlled precisely. Moreover, incorporation of Aliquat 336 into the chitosan backbone could significantly enhance its metal ions extraction ability. It has been shown to have much improved affinity for Pb " than pure chitosan. This may be explained in that the new strategy doesn t reduce the original amino active sites besides, the synergistic effect between cation and anion also contributes to the enhancement of adsorption capabilities. On the other hand, the effort to increase selectivity of the adsorbent for one metal ion over others is to make the adsorbent sterically efficient with that metal ion only. The new chitosan-... 

Acid-base neutralization Chemical extraction and leaching Ion exchange... 

To satisfy the Resource Conservation and Recovery Act (1977) and its amendment for hazardous and solid waste (1984), the 80(K) Series Methods have been designed to analyze solid waste, soUs, and groundwater. In particular, methods 8240/8260 require the use of a purge-and-trap device in conjunction with packed or capillary GC/MS, respectively, for the analysis of purgeable organic compounds. Methods 8250/8270 concern analyses for the less-volatile bases, neutrals, and acids by GC/MS after extraction from the matrix by an organic solvent. 

Base, neutral, and acid compounds, which may be less volatile, are extracted from the matrix with organic solvents. 

The mixture was stirred for 2 hours, heated at 60° to 70°C for 1 hour and poured into 2 liters of H O. The resulting suspension was extracted with ether, the ether layer separated and the ether removed under vacuum. A gummy mass remained which was dissolved in decalin and the solution was partly distilled to remove excess chlorobromide. After removal of most of the decalin under vacuum, the residue was treated with a large excess of N-( -hydroxyethyl)-piperazine and heated on a steam bath for 2 hours. This material was extracted with dilute aqueous HCI, this acid layer neutralized with aqueous base and the resulting oil extracted into ether. The ether layer was washed with water until the washings were neutral and dried over anhydrous potassium carbonate. On treatment with maleic acid in ether a yellow solid separated which was recrystallized from isopropanol. This yellow solid had MP 175° to 177°C. 

A mixture of 31 5 g (0.1 mol) of 2-chloro-9-(3 -dimethylaminopropylidene)-thiaxanthene (MP 97°C) and 100 g of N-( 3-hydroxyethyl)-piperazine is heated to 130°C and boiled under reflux at this temperature for 48 hours. After cooling, the excess of N-( 3-hydroxyethyl)-piperazine Is evaporated in vacuo, and the residue is dissolved in ether. The ether phase is washed with water and extracted with dilute acetic acid, and 2-chloro-9-[3 -N-(N - -hydroxy-ethyD-piperazinylpropylidene] -thiaxanthene separated from the aqueous acetic acid solution by addition of dilute sodium hydroxide solution to basic reaction. The free base is extracted with ether, the ether phase dried over potassium carbonate, the ether evaporated and the residue dissolved in absolute ethanol. By complete neutralization of the ethanolic solution with a solution of dry hydrogen chloride in absolute ethanol, the dihydrochloride of 2-chloro-9-[3 -N-(N -(3-hydroxyethyl)-piperazinylpropylidene] -thiaxanthene is produced and crystallizes out as a white substance melting at about 250°C to 260°C with decomposition. The yield is 32 g. 

One-tenth mol (20 g) of benzhydryl chloride was mixed with 0.19 mol (19 g) of N-methyl-piperazine and about 10 cc of benzene and the whole was heated on the steam bath four hours. The contents of the flask was partitioned between ether and water, and the ethereal layer was washed with water until the washings were neutral. The base was then extracted from the ethereal layer by N hydrochloric acid and the extract, made acid to Congo red paper, was evaporated under vacuum, 29.5 g of the pure dihydrochloride of N-methyl-N -benzhydryl piperazine was recovered from the residue by recrystallization from 95% alcohol melting above 250°C with decomposition. 

A solution of 5 g of bis(3-methylsulfonyloxypropyl)amine hydrochloride in 20 ml of ice water is neutralized with 1 N sodium carbonate solution. The resulting amine base Is extracted with five 20 ml portions of chloroform. The combined extract is dried over anhydrous sodium sulfate, the solvent is distilled off under reduced pressure, and the residue is dissolved in 20 ml of ethanol. To the ethanol solution Is added slowly with stirring under ice cooling a solution of 2.6 g of p-toluenesulfonic acid in 30 ml of ethanol. The white precipitate formed is collected by filtration and recrystallized from ethanol to give 5.0 g of white crystalline bis-(3-methylsulfonyloxypropyl)amine p-toluenesulfonate melting at 115°C to 116°C. 

Generally, it has been found that the organic acids and bases do exist in aqueous solution as equilibrium mixtures of their respective neutral as well as ionic forms. Thus, these neutral and ionic forms may not have the same identical partition coefficients in a second solvent therefore, the quantity of a substance being extracted solely depends upon the position of the acid-base equilibrium and ultimately upon the pH of the resulting solution. Hence, extraction coefficient (E) may be defined as the ratio of the concentrations of the substance in all its forms in the two respective phases in the presence of equilibria and it can be expressed as follows ... 

Greenberg AE, Cleseeri LS, Eaton AD. 1992. Method 6410 Extractable base/neutrals and acids liquid-liquid extraetion gas ehromatographic/mass spectrometric method. Standard methods for the examination of waste and wastewater, 18th edition, American Public Health Assoeiation, Washington,... 

Thus there is considerable incentive to find extractants that could tolerate higher quantities of solids in H2SO4 leach liquors. Stripping of uranium from the Amex process extractant and subsequent regeneration of the amine solvent also consume considerable quantities of acid and base. Recovery of uranium from H2SO4 solutions would be simplified if a convenient neutral extractant could be found. An extractant with better selectivity for vanadium and molybdenum than HDEHP and long-chain amines is also desirable. 

Distinctions between water-soluble fractions of mixed hydrocarbons may be made by using solvent extraction of the water-soluble base/neutral and acid fractions with methylene chloride (EPA 1991c Thomas and Delfino 1991a). This separation of base/neutral and acid fractions will permit the GC resolution of the type of water soluble hydrocarbons present in the aqueous phase. Hexane has also been used as a solvent (DellAcqua and Bush 1973), as has pentane (Coleman et al. 1984). 

APHA. 1992a. M-6410, extractable base/neutrals and acids. In Greenburg AE, Clesceri LS, Eaton AD, eds. Standard methods for the examination of water and wastewater. 18th ed. Washington, DC American Public Health Association, 6-77-6-89. 

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