Amberlite solvent extraction

This chapter provides some insight into the chemistry of a number of commonly used polymeric sorbents. Particular focus is placed on the chemical identification of contaminants typically associated with each of the following types of polymeric sorbents Amberlite XAD resins, Ambersorb XE resins, and PUF. Emphasis is placed on the chemical speciation of solvent-extractable organic contaminants present in a number of these sorbents as received from the manufacturer. Both qualitative and quantitative data on a micrograms-per-gram (parts-per-million) basis are provided as determined by combined gas chromatography-mass spectrometry (GC-MS). 

Many different sample preparation procedures have been employed, ranging from simple filtration of juice products to solvent extraction, and extraction by SPE using C, 8, Sephadex LH-20 (49,50,52), and Amberlite XAD-2 (51,54,57). The Amberlite XAD-2 cleaning step has been used for many phenolic extracts, especially for fruit purees, to remove the sugars and other polar compounds. However, due to the low recovery rate with Amberlite XAD-2 for certain phenol glycosides, a modified sample preparation technique is needed, especially for quantification of ar-butin in pear juice and blends (54). Figure 6 describes the fractionation procedure for phenolics using a Sephadex LH-20 column (58). 

To remove the feedback regulation mechanism and to avoid product degradation various adsorbents have been used for the in situ separation of plant cell cultures as shown in Table 1. In situ removal with polymeric adsorbents stimulated anthraquinone production more than the adsorbent-free control in Cinchona ledgeriana cells [35]. It was found that nonionic polymeric resins such as Amberlite XAD-2 and XAD-4 without specific functional groups are suitable for the adsorption of plant metabolite [36]. The use of the natural polymeric resin XAD-4 for the recovery of indole alkaloids showed that this resin could concentrate the alkaloids ajmalicine by two orders of magnitude over solvent extraction [37] but the adsorption by this resin proved to be relatively nonspecific. A more specific selectivity would be beneficial because plant cells produce a large number of biosynthetically related products and the purification of a several chemically similar solutes mixture is difficult [16]. 

The aldehyde is trapped with high volume samplers suspended in mid-canopy drawing 25 - 30 m /hr of air through a bed of 20 g of Amberlite XAD-2 resin. Originally the pheromone was derivat-ized to the pentafluorobenzyl oxime after solvent extraction from the resin (8). This was followed by silica gel column clean-up and quantitation by capillary GC with electron capture detection. This gave satisfactory results but was tedious and expensive. 

Lipopholic products are usually separated by extraction of the filtered broth, or the whole culture including the biomass, with water immiscible organic solvents, followed by separation of the solvent extracts and concentration in a vacuum evaporator. Chloroform, dichloromethane and ethyl acetate have been widely used as extraction solvents, however, 4-methyl-2-pentanone (methyl isobutyl ketone) appears to be the solvent of choice in the case of steroid substrates. Hydrophilic products, which cannot be extracted by organic solvents, can be isolated by ion exchange or by selective adsorption to polymeric resins (e.g., Amberlite XAD-resins). Resins of a wide range of polarity are available and lipophilic compounds can also be separated by this method. Final purification is accomplished in the usual way by crystallization, distillation or column chromatography. Preparative HPLC is a powerful tool for purification of small product quantities. 

Purification of the analogs was carried out as before by solvent extraction, adsorption, and elution (solid phase extraction) from a column of Amberlite XAD16, followed by loading of the sample onto a preparative HPLC column (Spherisorb ODS2, 5- Lun particle size), which was washed with 25% acetonitrile/water, then squalestatins 1 and analogs were eluted with 60% acetonitrile/water. A set of final preparative HPLC steps were carried out to resolve each of the analogs and the parent compound. The products isolated are shoivn in Fig. 6 (15,16) see Note 6). 

Different types of Amberlite XAD resins with unique physical and chemical properties have been available. Their use for adsorption of polar organic molecules directly out of biological samples has been demonstrated with pharmaceuticals [263], plant nucleotides [264], plant growth hormones [265], and various steroids [262,268]. In the last case, ample evidence is now available that the use of these resins causes substantially better recoveries of more polar steroid metabolites [262,268] than the previously employed solvent extractions. Setchell et al. [262] used the organic resins and modified dextranes for a complete fractionation of urinary steroid conjugates. Their general procedure (Fig. 3.15) involves the initial sample adsorption and several... 

The following abbreviations are used UV = ultraviolet oxidation CO = chemical oxidation SE = solvent extraction XAD = adsorption on Amberlite XAD-2 resin AAS = atomic absorption spectrophotometry S = visible spectrophotometry XRF = X-ray fluorescence spectroscopy NAA = neutron activation analysis. 

Aluminum(III) hydroxyfluorides minerals, 846 Alzheimer s disease aluminum removal, 770 Amberlite LA 2 solvent extraction palladium and platinum, 809 Americium breeder reactor fuels Purex process, 955 reprocessing, 954 Purex process, 946,950 sequestering agents, 962 Americium(III) complexes carbonates... 

Amberlite XAD2, because the interaction between the alkyl chains of extractant molecules and the macroporous support would lower the vibrational frequencies. Thus it may be concluded that these weak interactions between the adsorbed molecule and the support are make efficient contributions to the extractant retention on the support. This may confirm the prevailing ideas on impregnated resins insofar as the extractant keeps its solvent extraction properties after the impregnation process. 

An impregnated resin prepared from PC-88A and Amberlite XAD7 beads was examined as the stationary column phase for the separation of rare earth [28]. The reagent, PC-88A, is frequently used as an extractant in rare earth separation by solvent extraction. As can be seen in Fig. 27, the distribution ratio at a given pH increases with decreasing ionic radii of lanthanides. The slope analysis for log D versus pH and log D versus concentration of PC-88A indicated that the present extraction mechanism was similar to that of the solvent extraction system. A mutual separation of Y-Gd, La-Pr-Nd, and Ho-Er-Tm was successfully attained with the present resin as the stationary phase and hydrochloric acid as the mobile phase. 

Cortina et al. [6,18,32] studied the efficiency of impregnated resins containing the active component of Cyanex 272 adsorbed onto Amberlite XAD2 for the extraction of Zn(II), Cu(II), and Cd(II) from dilute solutions in nitrate and chloride media. The metal distribution studies show, as described in Sect. III.B, that the extraction of these metal ions involves reactions similar to those in solvent extraction systems. The extraction results indicate that Zn(Il) is adsorbed more selectively than Cu(II) and Cd(II), making possible the quantitative separation of Zn(II) from the other two [6], No significant differences were found on comparison of the extraction efficiency of these resins with Levextrel 807 84 resins [35]. 

The residual sediment after organic solvent extraction was extracted repeatedly with 0.2N NaOH to isolate the fulvic/humic acid fraction. Humic acid was then precipitated with hydrochloric acid to separate it from fulvic acid in the aqueous phase. Fulvic acid was purified by adsorption and subsequent elution from a column of Amberlite resin. Humic acid was purified by redissolving in NaOH and reprecipitation with hydrochloric acid. The residual sediment was then treated sequentially with hydrofluoric acid of increasing concentration to remove the silicates, washed several times with water and then dried to recover protokerogen (Stuermer et al, 1978). Procedure blank for each compound class fraction was dso combusted for carbon dioxide measurement. 

Solvent extraction of acetic acid from dilute aqueous industrial streams by commercial organic bases(such as various amines(Amberlite s.Adogen s.Alamine s etc.) and tri-octyl phosphine oxide(TOPO) )... 

A sequential analysis protocol includes three steps (1) extraction in water or other appropriate solvent for the colorant, (2) purification or concentration of the colorant, and (3) separation coupled with detection of the target molecule. Different methods of extracting synthetic colorants from foods have been developed using organic solvents followed by SPE protocols using as adsorption support RP-C18, amino materials, or Amberlite XAD-2. Eor qualitative evaluations, the easiest option for separating colorant molecules from unwanted ingredients found in an extract is SPE on polyamide or wool. 

Principle Instead of long-lasting extraction with different organic solvents, acids or bases in the Soxhlet apparatus is unsuitable for the extraction of most flavonoids, the Amberlite IR-45 (OH) ion-exchange resin was used for the extraction of plant phenolics. 

The chromatographic determination of AEs in the environment has been extensively reviewed [3,4], AEs have been extracted from the aqueous matrix, among others, by solvent sublation [65], LLE [66], SPE with Amberlite XAD-2 [67], cartridges [68-73] (i.e. C1 Ci8, GCB, C8) or Cis disks [74] and matrix solid-phase dispersion for bioconcentration studies in fish samples [75],... 

Last but not least, catechols are highly water-soluble (the water solubility of catechol is approximately 1 g per 2.3 mL of water), which makes it difficult to directly extract them in situ from reaction media with organic, water immiscible solvents. Nevertheless, extraction of catechols from aqueous systems with hydro-phobic polymers such as the polystyrene-based resin Amberlite XAD-4 is... 

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