Chemically modified polymeric resins for solid-phase extraction and group separation prior to analysis by liquid or gas chromatography
Polystyrene divinylbenzene (PS/DVB) was chemically modified by the introduction of acetyl, sulfonic acid, and quaternary ammonium groups for solid-phase extraction (SPE). These groups increase the hydrophylicity of the resin surface, making it more efficient for the extraction of polar organic molecules from liquid samples;A resin functionalized with an acetyl group was impregnated in a polytetrafluoroethylene membrane and used for the extraction and concentration of phenolic compounds from aqueous samples. The introduction of the acetyl group created a surface easily "wetted", making it a very efficient adsorbent for polar compounds in water. The membrane stabilized the resin bed, allowing for more efficient kinetics and thus higher flow rates and larger sample volumes;Partially sulfonated high surface area resins are used to perform an extraction and group separation of an aqueous mixture of neutral and basic organics. The bases are adsorbed electrostatically to the sulfonic acid groups on the resin. The neutrals are adsorbed hydrophobically onto the unreacted surfaces of the resin. A two-step elution process is then used to separate the two fractions. The neutral fraction is first eluted with an organic solvent, followed by the basic fraction with a basic organic eluant. Similar separations are performed in non-aqueous eluant;A partially functionalized anion exchange resin is used to concentrate and separate organic acids and phenols from neutrals. The acids are adsorbed electrostatically to the quaternary amine groups on the resin. The neutrals are adsorbed due to hydrophobic interactions with the unreacted surfaces of the resin. The pH of the aqueous solution is raised sufficiently to ensure that the acids are present in their anion form, causing them to be electrostatically bound to the anion exchange groups on the resin. The neutrals are eluted first with an organic solvent, followed by the acids in an acidic organic eluant. Carboxylic acids are analyzed by HPLC and phenols are analyzed by GC. Similar separations have been performed in nonpolar media, with the neutral fraction being unretained.