Solid phase extraction interactions

This sample preparation involved, firstly, an extraction and the elimination of the solid matrix by filtration and, secondly, a concentration procedure employing a solid phase extraction cartridge. The compounds of interest were separated solely by dispersive interactions with the reversed phase. In the example given, the corn meal was spiked with the aflatoxins. 

Solid phase extraction (SPE) involves the separation of components of samples in solution through their selective interaction with and retention by a solid, particulate sorbent. SPE depends on differences in the affinities of the various components of the sample for the sorbent. The mechanisms of the interactions are virtually identical to the sorption processes that form the basis of liquid chromatographic separations (p. 80). The choice of solvent, the pH and ionic strength of aqueous solutions, and the chemical nature of the sorbent surface, especially its polarity, are all of importance in controlling the selectivity and efficiency of an extraction. 

Agonists are particularly suited to reversed-phase solid-phase extraction due, in part, to their relatively nonpolar aliphatic moiety, which can interact with the hydrophobic octadecyl- and octyl-based sorbents of the cartridge (472, 473, 475, 480,486, 487). By adjusting the pH of the sample extracts at values greater than 10, optimum retention of the analytes can be achieved. Adsorption solid-phase extraction using a neutral alumina sorbent has also been described for improved cleanup of liver homogenates (482). 

As mentioned above, most MIPs are synthesized in organic solvents to preserve the hydrogen and electrostatic interactions between template and monomer. However, for the application to solid-phase extraction (SPE) where the target is most of the time in water samples or in biological fluids, a lot of studies have been carried out to examine the influence of binding media parameters (solvent polarity and composition, buffer pH, concentration, ionic strength, etc.) with the aim of attenuating non-specific adsorption of the analyte due to hydrophobic interactions which predominate in such media. For a recent review, see Tse Sum Bui and Haupt [95]. 

B. Law, Secondary interactions and mixed-mode extraction, in N. J. K. Simpson, ed., Solid-Phase Extraction Principles, Techniques, and Applications, Marcel Dekker, New York, 2000, pp. 227-242. 

V. Marko, L. Soltes, and I. Novak, Selective solid-phase extraction of basic drugs by Cl8-silica. Discussion of possible interactions, J. Pharm. Biomed. Anal., 5 297-301 (1990). 

Solid-phase extraction (SPE) is a purification technique based on the extraction of a compound (or a mixture of compounds) from a solution through absorption on a solid support The main physical principles involved in the extraction process are ionic interactions between acidic and basic species, and polar and/or nonpolar... 

---