Amberlite® XAD resins

POLYMERIC SORBENTS are frequently used in environmental analytical schemes for the isolation and/or preconcentration of trace organic contaminants from air and water matrices. Commercially manufactured polymeric sorbents such as Amberlite XAD resins, Ambersorb XE resins, Tenax (diphenyl-p-phenylene oxide), and polyurethane foam (PUF) have been used extensively for the collection of trace organic contaminants from ambient air, process streams (i.e., flue gas), and a variety of aquatic matrices including industrial effluents, ground water, surface water, and potable water supplies. Currently, these materials... 

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). 

Ambersorb XE Resins. All instrumental analyses were identical to those employed in the analysis of the Amberlite XAD resins as described previously (2). 

Amberlite XAD Resins. Amberlite XAD resins are synthetic adsorbents structurally composed of a styrene-divinylbenzene copolymer. Because of the polymeric production process, users are cautioned that these resins do contain significant quantities of preservatives and monomers as received from the manufacturer, Rohm and Haas (3,4). 

Table I. Chemical Characterization and Quantitation of Organic Contaminants Extracted from Amberlite XAD Resins...

Various separation methods have been used to isolate, fractionate, and characterize humic materials. Originally it was fractionation, based on solubility differences of humic components in diluted alkalis and acids, which laid the ground work for the first classifications of humic substances (HS) in the 19th century (Mulder, 1861 Sprengel, 1837) and provided for operational definition of HS (Kononova, 1966). And now, alkali extraction is the method of choice for isolating HS from solid humus-containing substrates like soil, peat, coal, and so on (Swift, 1996), while hydrophobic resins (e.g., Amberlite XAD resins) are typically used to extract HS dissolved in natural waters (Aiken, 1985). Initial research on HS began with the used simple separation methods to prove, examine, and define characteristics of components of humic matter (Oden, 1919).Today, however, advances in HS research require ever more sophisticated techniques of separation combined with structural analysis (Orlov, 1990 Stevenson, 1994). 

Amberlite XAD resin Amberlite XAD resin will remove a broad range of relatively lower molecular weight organic contaminants. Unlike carbon, toxicants can often be recovered from XAD resin using methanol or other solvents. Samples are passed through a column (or mixed as a slurry) containing the resin, and the pH re-adjusted to pH i prior to testing. 

Tomas-Barberan, F.A. Blazquez, M.A. Garcia-Viguera, C. Ferreres, F. Tomas-Lorente, F. 1992. A comparative study of different Amberlite XAD resins in flavonoid analysis. Phytochem. Anal. 3 178-181. 

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. 

Andersson K, Levin JO, Lindahl R. 1982. Sampling of ethylene glycol and ethylene glycol derivatives in work-room air using amberlite XAD Resins. Chemosphere 11(11) 1115-1119. 

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... 

Various materials have been used to adsorb organochlorine compounds from natinal waters. They include activated charcoal urethane foam plugs polyurethane foam coated with adsorbents a porous polymer (Tenax GC) a mixture of activated chmcoal powder, MgO powder and refined diatomaceous earth Carbowax4000 and n-undecane on Chromo-sorb DMCS Serdolit and Amberlite XAD resins (references were given in the second edition). The last material has been used most successfully (IOC, 1993). The use of XAD resin has been described in some detail by Dawson (1976). Problems initially encountered with cleaning of this adsorbent have been solved in the meantime. Extremely low blank values can now be obtained for XAD-2 columns. Their use allows reliable determinations of CBs present in seawater at levels as low as 0.005-0.1 pg/L. 

Cationics. XAD resin has been successfully used for concentration of cationics from water (55). Kawabata and coworkers have found that a specially prepared resin material of poly(hydroxystyrene) highly crosslinked with divinylbenzene is a superior adsorbent for cationic surfactants (67). The mechanism appears to be acid-base reaction rather than ion exchange, since inorganic cations are not adsorbed. The cationic is recovered and the resin regenerated by elution with methanol. The capacity of this resin for cationics is higher than that of Amberlite XAD resins as well as traditional cationic exchange resins. The presence of salts or alkali in the matrix increases the capacity. 

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