Anion latex agglomerated

Fig. 1. Simultaneous separation and detection of anions and cations on a latex agglomerate column. Column Dionex HPIC-CS5 cation exchange column (250X2 mm) with precolumn HPIC-CG5 (50 X 4 mm) eluent 0.5 mM copper sulfate, pH 5. 62 flow rate 0.5 ml/min sample volume 20 gl containing 0.1 m M of each ion detection two potentiomet-ric detectors equipped with different ion-selective electrodes in series. Peaks (1) chloroacetate, (2) chloride, (3) nitrite, (4) benzoate, (5) cyanate, (6) bromide, (7) nitrate, (8) sodium, (9) ammonium, (10) potassium, (11) rubidium, (12) cesium, (13) thallium. Reprinted with permission from [10].

Review of different latex-agglomerated anion exchangers... 

In 1994, Lamb et al. developed a series of cryptand-based anion separators. The biggest advantage of cryptand columns, used in gradient elution mode, is the ability to elute non-polarizable and polarizable anions in the same run, which is very difficult (or even impossible) with latex-agglomerated anion exchangers and aminated grafted polymers. ... 

Like anion exchangers, cation exchangers are divided into polymer-based cation exchangers (PS-DVB, EVB-DVB, polymethacrylate, and polyvinyl copolymers), latex-agglomerated cation exchangers, silica-based, and other (e.g., crown ether, aluminia materials).Modern cation exchangers contain sulfonic, carboxylic, car-boxylic-phosphonic, and carboxylic-phosphonic-crown ether functional groups. 

Latex cation exchangers were introduced by Dionex Corp. 10 years later than latex-agglomerated anion exchangers. These types of cation exchangers consist of a weakly sulfonated PS-DVB substrate with latex beads with a very small diameter agglomerated on its surface by both electrostatic and van der Waals interactions. 

Latex-agglomerated anion exchangers are chemically very stable. Even 4 mol/L sodium hydroxide is unable to cleave the ionic bond between the substrate particle and the latex beads. The selectivity is altered by changing the chemical... 

Review of Different Latex-Agglomerated Anion Exchangers... 

Armed with several anion-exchange columns and an eluent solution of 2.0 mM KHP (pH 5.0), Siriraks et al. set out to determine why the elution order they observed (Zn-Pb-Cu) was different than that reported by Jenke and Pagenkopf [20]. They studied the chromatographic behavior of Pb(II), Zn(II), and Cu(II) on four different anion-exchange columns in an attempt to elucidate the mechanism of retention for the three cations. The following columns were used in the study silica-bonded from Vydac (302.IC) polystyrene-divinylbenzene (PS-DVB) from Hamilton (PRPX-100) pol)miethacrylate from Waters (IC-Pak) and a latex agglomerated PS-DVB from Dionex (AS-4). 

When a large amount of anionic emulsifier was initially present in the reactor, many particles were formed. This number decreased during the latex preparation because not enough emulsifier was added with the monomer feed emulsion to keep the surface of the particles covered. Controlled agglomeration of polymer particles occurred to a stage where... 

The particle size distribution of various latices, prepared via the above monomer emulsion addition technique, was determined with the aid of an ultracentrifuge. It was found to be invariably of the log-normal type, as shown in Figure 6, independent of the way the particles are formed. This illustrates that the agglomeration of particles during latex preparation, when the initial reactor charge contained more than 15% of the anionic emulsifier, is a random and not a selective process. 

Latex-based anion exchangers are comprised of a surface-sulfonated polystyrene/divi-nylbenzene substrate with particle diameters between 5 pm and 25 pm and fully animated porous polymer beads of high capacity, which are called latex particles. The latter have a much smaller diameter (about 0.1 pm) and are agglomerated to the surface by both electrostatic and van-der-Waals interactions. A scanning electron micrograph of this material is shown in Fig. 3-12. Hence, the stationary phase features three chemically distinct regions ... 

By agglomerating acrylate-based latex beads on polystyrene/divinylbenzene substrates, a separation of chlorate and nitrate can also be achieved, which was previously not possible using conventional ion exchangers. These two anions exhibit the same interactions with both latex-based anion exchangers and directly aminated substrates and, thus, co-elute at these stationary phases. Therefore, ion-pair chromatography was used for this separation, which allows baseline separation of chlorate and nitrate due to their... 

Regarding the type of inorganic electrolyte, there was no marked difference in effectiveness between the monovalent cations, but preliminary experiments using SBR latexes with emulsifiers which, in contrast to oleate, do not form insoluble salts with divalent cations, demonstrated that in this case PEO was less effective. Findings in earlier sensitization experiments were similar (29, 30). As to the type of anionic emulsifier, a slight correlation between emulsifier surface activity and agglomeration rate was observed. 

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