Solid extractants anion extraction

Use liquid-solid extraction cartridge or disk as anion exchange column. Add AG-1-X8 resin solution dropwise. 

There are several methods available for the extraction of bile salts from serum or plasma. The most convenient methods utilize some form of liquid-solid extraction. An early procedure involved the anion-exchange resin, Amberlyst A-26 (S8), but considerable time and effort was required to perform column chromatography and to concentrate the eluate from the column. The introduction in 1972 of the neutral resin, Amberlite XAD-2, improved the ease of extracting bile acids and their conjugates from serum samples (M6). Further improvement occurred in 1977 with the description of a batch extraction technique using the related neutral resin, Amberlite XAD-7 (B5). With this technique, serum is diluted in 0.1 M sodium hydroxide to release bile acids from albumin and mixed with resin for 1 hour. After washing the resin in dilute alkali, bile acids are eluted with methanol, which cdn be removed on a rotary evaporator (B5). 

Quite drastic conditions are required to desorb cationic surfactants from solids. Extraction with methanolic HCl resulted in optimum recovery. However, the extract has to be purified by extraction into chloroform in the presence of disulphine blue or LAS. Einally, cleavage of the ion pairs is done on ion exchangers. Hellmann used an AI2O3 column to purify sewage sludge extracts. In this way, he was not only able to separate impurities but also to elute cationic and anionic surfactants stepwise with different solvent systems. 

The mechanism of metal extraction by using solid extractants can be categorized as cation extraction and anion extraction. These extraction mechanisms are dependent... 

Supercritical fluid extraction with CO2 containing at least 10% methanol is effective for removing distearyldimethylammonium chloride from sediment and sewage sludge as an ion pair. Because anionic surfactants are already present in sludge, no anion need be added to insure ion pair formation. SEE is not more complete than conventional liquid-solid extraction with methanolic HCl, but is more rapid. There is some indication that less of materials other than cationic surfactants is extracted by SEE compared to conventional extraction (150,151). 

SOLID-PHASE SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF ANIONIC SURFACTANTS WITHOUT LIQUID-LIQUID EXTRACTION... 

A new class of solvents called ionic liquids has been developed to meet this need. A typical ionic liquid has a relatively small anion, such as BF4, and a relatively large, organic cation, such as l-butyl-3-methylimidazolium (16). Because the cation has a large nonpolar region and is often asymmetrical, the compound does not crystallize easily and so is liquid at room temperature. However, the attractions between the ions reduces the vapor pressure to about the same as that of an ionic solid, thereby reducing air pollution. Because different cations and anions can be used, solvents can be designed for specific uses. For example, one formulation can dissolve the rubber in old tires so that it can be recycled. Other solvents can be used to extract radioactive waste from groundwater. 

Wheat samples are extracted with dilute ammonia on the ASE200. The extracts are amended with isotopically labeled internal standards. The extracts are purified by sequential octadecyl reversed-phase solid-phase extraction (Cig SPE) and ethylenediamine-iV-propyl anion exchange (PSA) SPE. The samples are analyzed by LC/MS/MS. This method determines crop residues of flucarbazone-sodium and A-desmethyl flucarbazone with a limit of quantitation (LOQ) of 0.01 mgkg for each analyte. 

Several methods have been used to separate the lanthanides chemically solvent extraction, ion exchange chromatography, HPLC using Q-hydroxyisobutyric acid and, in limited cases, selective reduction of a particular metal cation.40-43 The use of di(2-ethylhexyl)orthophosphoric acid (HDEHP) for the separation of various rare-earth elements via solvent extraction has also been reported.44 16 This separation method is based on the strong tendency of Ln3+ ions to form complexes with various anions (i.e., Cl- or N03 ) and their wide range of affinities for com-plexation to dialkyl orthophosphoric acid. When the HDEHP is attached to a solid phase resin, the lanthanides can be selected with various concentrations of acid in order of size, with the smallest ion being the most highly retained. 

Ester 324 is hydrolyzed to acid 325 by refluxing in 10% NaOH. In a reaction with thionyl chloride, acid 325 is converted to acid chloride 326, which is isolated as a solid in 96% yield and consecutively converted into amide 327 in 85% yield. Treatment of amide 327 with LDA extracts a proton from the methyl group. The generated anion is trapped by added benzonitrile. Subsequent cyclocondensation of the obtained imine anion with the amide group provides derivative 328 in 62% isolated yield (Scheme 50) <2003EJM983>. 

Liquid ion-exchangers have been discussed in the section on solvent extraction (p. 65). They can be used in column form by coating them on to a solid support such as cellulose powder or Kel-F (polytrifluorochloroethylene). Tris-n-octylamine (TNOA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) behave as strong-base and strong-acid exchangers for anions and cations respectively. 

Wang J, Ashley K, Marlow D, England EC, Carlton G. Field method for the determination of hexavalent chromium by ultrasonication and strong anion-exchange solid-phase extraction. Anal. Chem. 1999 71 1027-1032. 

In one study, however, atmospheric pressure chemical ionisation (APCI)-MS was applied for the simultaneous determination of LAS and octylphenol ethoxylates (OPEO) in surface waters after preconcentration by solid-phase extraction (SPE) on Cis cartridges [1]. In the chromatogram from a Ci-reversed phase (RP) column, peaks arising from both the anionic LAS and the non-ionic OPEO were detected after positive ionisation, while in negative ionisation mode, OPEO were discriminated and only the anionic surfactant was observed. Surprisingly, the relative sensitivity for detection of LAS was approximately five times higher in positive ion mode, which led the authors to the conclusion that this ionisation mode was desirable for quantitative work. 

With the aim of minimising the time taken in the preconcentration, and extending the chemical analysis of surfactants to more complex aqueous matrices in which very low detection limits are required, preconcentration techniques using solid-liquid extraction with various adsorbent materials, such as XAD [27] and anionic exchange resin [28] have been developed. 

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