Amberlite XAD copolymers in reversed phase gravity flow and high pressure liquid chromatography

Abstract

Rigidly porous Amberlite XAD copolymers with large surface areas were Investigated as packings for chromatographic applications and were shown to differ In adsorption power. Batch distribution coefficients and retention volumes (capacity factors) were determined for substituted benzenes, anilines, phenols, benzoic acids, sulfonic acids, and phenoxyacetlc adds at different experimental conditions. Variables that influence the Interactions between organic molecules and the copolymers Include: pH, type and concentration of organic solvent mixed with water or with other organic solvents, type, number, and position of substituents In the organic molecule, and the concentration of added electrolyte. Electrolyte and pH are the most significant variables for organic acids and bases. These data provide a basis for choosing eluting conditions and adsorbent for separation, stripping, and concentrating applications In reversed phase gravity flow and high pressure liquid chromatography.The commercially available Amberlite XAD series of copolymers, which have large surface areas and rigid, near permanently porous structures, have been shown to be good adsorbents for a wide variety of organic compounds. Many examples are available in the literature which describe the removal of impurities in sugars, meat products, and water, and the isolation of steroids, carotenoids, toxic drugs, and other biologically important compounds from urine or blood, utilizing a stripping column usually made with XAD-2 macroparticles (1-7). XAD-2 stripping columns are now routinely used in screening urine for drugs of abuse (8-10). Recently, the use of XAD-2 for stripping drugs and related compounds from urine, blood, tissue samples, and stomach contents was reviewed (11). In general, the conditions utilized for stripping were derived empirically.The XAD copolymers have not been extensively used in analytical columns in liquid chromatography. Macro XAD-2 particles and gravity flow elution were used in the separation of chlorinated and nitrated phenol derivatives (1) while micro XAD-2 particles and high pressure elution were used in the separation of aniline and pyridine derivatives (12). Subsequently, XAD-7 columns were used to separate phenols (13) and IV-methyl anilines and methyl substituted phenols were separated on XAD-2 columns ( 14) by HPLC. The nature of the interaction between the XAD copolymers and organic compounds was also considered in these (1,(12)(13)(14) and other studies (15,16).In this report, experiments which demonstrate the significance of the parameters that influence the sorption of organic compounds on XAD columns, are described. These include: structure of the XAD copolymer and of the organic compounds being separated, pH, salt concentration, and type and concentration of the solvents in the eluting system. With these data it should be possible to predict optimum conditions for stripping and quantitative separations and to serve as a basis for suggesting other polymeric structures that might be useful as chromatographic packin...

A micromethod for the isolation of drugs from blood using Amberlite XAD-2

“…Optimal recoveries were obtained by careful selection of the extraction conditions. A decrease of the recovery was found if acidic drags were adsorbed to the resin from alkaline media or basic drags from acidic media, an effect already attributed by other authors [6,[12][13][14][15][16][17] to be due to the unpolar structure of the resin which preferably adsorbs unpolar unionisized compounds. Therefore, the drugs were divided into two groups, one containing the basic and neutral drags, which were adsorbed from alkaline blood, and another containing the acidic ones, which were adsorbed from slightly acidic blood.…”

Literature Review and Evaluation of Solid Sorbents for Water Sampling of Explosives

“…The acrylate esters are expected to show higher capacity for polar sorbates than the styrene divinylbenzene resins (Pietrzyk and Chu, 1977). Chromosorb 104, an acrylonitrile divinylbenzene resin, has shown some success at sampling nitro compounds in air (Pellizzari et al, 1975a).…”

“…The space between the agglomerated microspheres is continuously porous. These resins are nonpolar and exhibit high sorbent capacity for nonpolar sorbates (Pietrzyk and Chu, 1977). The structure of a typical styrene divinylbenzene resin, one of the Amberlite XAD series, is shown in Figure 1.…”

“…The structures for the other resins are similar. Because of the polarity of the acrylic esters, these resins exhibit a greater affinity for polar sorbates than the styrene divinylbenzene resins (Pietrzyk and Chu, 1977).…”

Determination of equilibrium constants from chromatographic and electrophoretic measurements

“…In chromatography, an effect of fast equilibria can be treated using a concept of limiting retention factors that has been used in reversed phase [17][18][19][20][21][22] as well as in ion-exchange [23] separation modes. Let's assume, for example, that fast equilibrium according to Eq.…”