Anion exchange stationary phase

Qiu, H., Jiang, S., and Liu, X., N-Methylimidazolium anion-exchange stationary phase for high-performance liquid chromatography, /. Chromatogr. A, 1103, 265-270,2006. 

Figure 4.5—Schematic showing successive exchanges of an analyte anion A and a counter anion E in the mobile phase in contact with an anion exchange stationary phase. Initially, the counterion E fixed on the stationary phase is exchanged with A present in the mobile phase. Then the elution inverses the phenomenon and regenerates the stationary phase with the E ions.

Lammerhofer et al. [127] demonstrated the use of a strong anion-exchange stationary phase, prepared in a monolithic format, for the separation of a mixture of four NSAIDs—ibuprofen, naproxen, ketoprofen, and suprofen. The separation, presented in Figure 29, was achieved in 13 min with high column efficiencies of up to 231,000 plates/m. 

Separations of common inorganic anions were carried out on three different surfactant-coated columns converted into anion exchange stationary phases by equilibration with cationic surfactants [26]. Several polarizable anions were analyzed under IPC conditions via sulfonium and phosphonium IPRs that showed distinct selectivity toward the anions based on the chaotropic or kosmotropic attitudes of both the anion and the IPR [27]. 

Fig. 1.5. High-performance liquid chromatographic separation of phosphorus compounds determined in soil leachate using a strong anion exchange stationary phase. Reprinted from Espinosa etal. (1999) with permission from the American Society of Agronomy.

The separation of nucleic acids by using strong anion-exchange stationary phases has become very popular (Gait et al., 1982 McLaughlin and Romanuik, 1982). The separations depend on the charge of... 

Buchberger (Buchberger, 1988) determined I- (among other ions) in water samples using an anion-exchange stationary phase (Vydac 302-IC) and methanesulphonic acid solution as the mobile phase. A post-column reaction detector was developed based on the reaction between iodide or bromide, chloramine-T and 4,4 bis (dimethylamino)diphenylmethane. The detection limit was ca. 20 pg iodide injected. 

Ions that are most commonly determined in food samples are inorganic anions, carboxylic acids, metal ions, and organic cations. Some anion-exchange stationary phases do not always allow a baseline-resolved separation of all inorganic and organic ions under isocratic conditions. 

Because of the development of analytical methods for determination of MC, especially in last decade, the most widespread analytical techniques for their determination are commercialized enzyme-linked immunosorbent assays and HPLC with diode array detectors of anion-exchange columns for this purpose were only sporadically reported with UV detection and isocratic or gradient ° elution. For anion-exchange stationary phase functionalized with diethylaminoethylene groups, better resolution for LR and YR was reported than for Cl8 columns.For separation of cyanobacterial toxins, including MC-LR and -RR, hydrophilic interaction HPLC with gel Amide-80 column and amide C16 column providing comparable resolution to that of conventional reversed-phase Cl8 columns were applied. 

Anion-exchange stationary phases described in Section 3.4.1.4 are based on colloidal anion-exchange particles (the so-called nanobeads or latex particles) that are electrostatically bound to the surface of nonporous surface-sulfonated or sur-face-carboxylated PS/DVB and EVB/DVB copolymer beads. This approach to stationary-phase design provides a number of advantages including the following ... 

Fig. 9. Molecular properties of a typical anion-exchange stationary phase.

---