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Organic acids isolation using resins

At present, soil derived humic matter and fulvic acids extracted from freshwater are available commercially and are commonly used to test techniques for DOM detection and also used as model compounds for trace metal chelation studies. The results obtained using these model compounds are frequently extrapolated to the natural environment and measurements on "real" samples provide evidence that this DOM is a good model compound. In the past, some investigators also made available organic matter isolated from marine environments using C18 resins. While these compounds come from aquatic sources, this isolation technique is chemically selective and isolates only a small percentage of oceanic DOM. Reference materials are not currently available for these compounds, which inhibits study of the role they play in a variety of oceanographic processes. [Pg.60]

Early studies using resins for isolation and analysis of trace organics, such as pesticides, PCBs, and organic acids, from small volumes of water showed excellent recovery and the potential of easy application to environmental samples. Isotherm studies in distilled water were used to define the sampling parameters for quantitative analysis of these compounds. Later, studies using resin samplers for large-volume environmental samples were extrapolated from the early low-volume resin work of Junk et al. (5,14) and Thurman et al. (27) (see Table I). [Pg.271]

Adsorption chromatography is an efficient way to isolate organic acids from large volumes of water. The nonionic, macroporous, Amberlite XAD-8 and the weak-base anion-exchange resin Duolite A-7 are two resins well suited for this purpose. These resins have been successfully used to extract organic acids from natural waters at sites where it was necessary to process thousands of gallons of sample. [Pg.306]

Desorption of the model compounds isolated on the quaternary XAD-4 (QXAD-4) resin column was accomplished by sequential elution with ethyl ether, methanol, ethyl ether, 0.1 N HCl/ether, 0.1 N HCl/methanol, and saturated HCl/methanol. The acidified organic solvents were used for acidic solute removal. [Pg.418]

Aiken, G. R., D. M. McKnight, K. A. Thorn, and E. M. Thurman. 1992. Isolation of hydrophilic organic acids from water using nonionic macroporous resins. Organic Geochemistry 18 567-573... [Pg.93]

Typically, seawater samples are acidified prior to extraction (pH 2-4) to proton-ate organic acids, and the compounds absorbed to resins are eluted with base for XAD resins and with organic solvents for Cjg resins. Aiken et al (1992) extracted 30-83% of the DOC in freshwater environments using XAD 8 and XAD 4 in series. For marine environments, Druffel et al (1992) reported the isolation of 23-39% of the DOC when XAD 4 was used in series with either XAD 8 (30-39% of total DOC) or XAD 2 (23—28% of total DOC). More recently Cjg resins have been used to isolate about 30% of total DOC from marine systems, and up to 50% from estuarine waters (Amador et al, 1990 Kaiser et al, 2003 Repeta et al, 2004 Simjouw et al, 2005). These resins are purportedly more successful than XAD-2, for example, at removing the colored DOM component from seawater. [Pg.97]

Humic substances are a broad class of organic compounds operationaUy defined by their solubility at different pHs and retention on hydrophobic resins (Aiken, 1988 Thurman, 1985). There are three operational sub-categories of humic substances humic acids, which are soluble at a higher pH but become insoluble at a pH < 2 (isolated using XAD-8 resin) fulvic acids, which are hydrophilic acids soluble under aU pH conditions (isolated using XAD-4 resin), and humin, which is insoluble at any pH (Ishiwatari, 1992). For a review of humic substances in aquatic systems, see Hessen and Tranvik (1998), Benner (2002), and Chapter 3 by Aluwihare and Meador, this volume. [Pg.1229]

Figure 1.10 HPLC analysis of organic acids in Cabernet Sauvignon wine using after sample preparation by C18 SPE followed by isolation of organic acids a 500-mg amine-quaternary resin (Figure 1.9). 1. tartaric acid, 2. malic acid, 3. lactic acid, 4. acetic acid, 5. citric acid, 6. pyruvic acid, 7. shikimic acid. Analytical conditions column C18 (250 x 4mm, 5 pun) at room temperature, detection at wavelength 210nm, sample volume injected 20p.L, solvent H3P04 5 x 10 3M with isocradc elution at flow rate 0.6mL/min (Flamini and Dalla Vedova, 1999)... Figure 1.10 HPLC analysis of organic acids in Cabernet Sauvignon wine using after sample preparation by C18 SPE followed by isolation of organic acids a 500-mg amine-quaternary resin (Figure 1.9). 1. tartaric acid, 2. malic acid, 3. lactic acid, 4. acetic acid, 5. citric acid, 6. pyruvic acid, 7. shikimic acid. Analytical conditions column C18 (250 x 4mm, 5 pun) at room temperature, detection at wavelength 210nm, sample volume injected 20p.L, solvent H3P04 5 x 10 3M with isocradc elution at flow rate 0.6mL/min (Flamini and Dalla Vedova, 1999)...
Reactions were quenched after 4 hr. In cases of treatment with resin, simple gravitation filtering was sufficient to isolate the resin from the sample. Subsequent assays for aldehyde (or peroxide) and boron were effected. When NaBH4 or (C2H5)4 NBH4 were used, samples were neutralized with excess aqueous hydrochloric acid. Organic and aqueous phases were separated when possible and both were subsequently analyzed for aldehyde (or peroxide). Weights of analyzed samples were noted percent reduction was calculated. [Pg.197]

Cycloaliphatic epoxy resins and epoxidized oils are prepared by epoxida-tion with peracids such as peracetic acid. The latter is low in cost, and few side reactions are encountered. Usually the peracid is not made in situ. Typically 25% peracetic acid in an organic solvent is used at -10 to - 15 C. The product is isolated by distillation after removal of the solvent, acetic acid and unreacted peracetic acid [13]. [Pg.102]

Isolation. Isolation procedures rely primarily on solubiHty, adsorption, and ionic characteristics of the P-lactam antibiotic to separate it from the large number of other components present in the fermentation mixture. The penicillins ate monobasic catboxyHc acids which lend themselves to solvent extraction techniques (154). Pencillin V, because of its improved acid stabiHty over other penicillins, can be precipitated dkecdy from broth filtrates by addition of dilute sulfuric acid (154,156). The separation process for cephalosporin C is more complex because the amphoteric nature of cephalosporin C precludes dkect extraction into organic solvents. This antibiotic is isolated through the use of a combination of ion-exchange and precipitation procedures (157). The use of neutral, macroporous resins such as XAD-2 or XAD-4, allows for a more rapid elimination of impurities in the initial steps of the isolation (158). The isolation procedure for cephamycin C also involves a series of ion exchange treatments (103). [Pg.31]

Phenol is produced through both natural and anthropogenic processes. It is naturally occurring in some foods, human and animal wastes, and decomposing organic material, and is produced endogenously in the gut from the metabolism of aromatic amino acids. Phenol has been isolated from coal tar, but it is now synthetically manufactured (EPA, 2002). Currently, the largest use of phenol is as an intermediate in the production of phenolic resins, which are used in the plywood, adhesive, construction, automotive, and appliance industries. Phenol is also used in the production of synthetic fibers such as nylon and for epoxy resin precursors such as bisphenol-A. [Pg.472]

The other isolation methods evaluated employed solid adsorbents to isolate the model solutes (6-8). The first of these used XAD-4, a macroreticular, polystyrene-divinylbenzene resin (Rohm and Haas), into which trimethylamine groups had been introduced (9). The purpose of the resulting quaternary ammonium functional groups was to allow more efficient adsorption of acidic compounds without an appreciable loss of capacity for hydrophobic compounds. This feature is important because the vast majority of the organic matter in potable water is neutral or acidic in nature (JO). [Pg.418]


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See also in sourсe #XX -- [ Pg.297 , Pg.298 , Pg.299 , Pg.300 , Pg.301 , Pg.302 , Pg.303 ]




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