Anion-exchange sorbents

Keywords anion-exchange sorbents cation-exchange sorbents Chernobyl drinking... 

Anion-exchange sorbents are made by treatment of cation -exchange filters in H-form by water solution of polyethylenimine. Amine... 

The treatment of the cation-exchange sorbents by 1% solution of polyethylenimine at 25°C during 1 hour was selected as the optimal condition for the anion-exchange sorbents production. Capacity (Cr6+) of the sorbents is 2.0 meq/g. 

The produced cationic and anionic exchange fibroid sorbents on the base of polyacrylonitrilic fiber were used to produce household water filters. The cloths of cationic and anionic exchange sorbents with mass of 50 g each one were reeled on a perforated cylinder with diameter of 10 mm and length of 15 mm. This cartridge could be easily replaced. Initial tap water... 

Relative extraction efficiencies of polar polymeric neutral, cation, and anion exchange sorbents (HLB, MCX, and MAX) for 11 beta antagonists and 6 beta agonists in human whole blood were probed.109 Initial characterization of MCX and MAX for acidic and basic load conditions, respectively, showed that both the agonists and antagonists were well retained on MCX, while they were recovered from MAX in the wash with either methanol or 2% ammonia in methanol (see Table 1.6). Blood samples were treated with ethanol containing 10% zinc sulfate to precipitate proteins and the supernatants loaded in 2% aqueous ammonium hydroxide onto the sorbents. After a 30% methanol and 2% aqueous ammonia wash, the analytes were eluted with methanol (HLB), 2% ammonia in methanol (MCX), or 2% formic acid in methanol (MAX). The best recoveries were observed with MCX under aqueous conditions or blood supernatant (after protein precipitation) spiked sample load conditions (see Table 1.7). Ion suppression studies by post-column infusion showed no suppression for propranolol and terbutaline with MCX, while HLB and MAX exhibited suppression (see Figure 1.6). 

The magnitude of the diffusion coefficients given in Table I can be compared with a value of 3.3 X 10 5 cm.2/sec. determined experimentally by Stokes (26) for HCl in bulk solution at infinite dilution. The pore diffusion coefficients listed in Table I for HCl vary by a factor of (2 - 4) X 10"2 from that given by Stokes. McNeill and Weiss (15) have indicated that active carbon can be considered as a weak-base anion-exchange sorbent. According to Helfferich (13), diffusion coefficients in such resins can be several orders of magnitude less than the corresponding bulk solution coefficients. The Cl" ion probably limits the rate of diffusion, since its mobility in aqueous solution is much less than that of the H30+ ion. Further evidence to support this conclusion has been obtained in the present work from determinations of pore diffusion... 

Figure 2.28. Interactions between analytes and ion-exchange sorbents (a) strong cation-exchange sorbent and (b) strong anion-exchange sorbent.

Anion-exchange sorbents for SPE contain weakly basic functional groups such as primary or secondary amines which are charged under low-pH conditions or strongly basic quaternary ammonium groups which are charged at all pHs. Cation-exchange sorbents for SPE contain weakly acidic functional... 

FIGURE 12 Plots of the approach distance a (in angstroms) versus k for the protein human serum albumin (HSA) (pi = 5.85, Mr = 69,000) measured with the strong anion exchange sorbent, Mono-Q, under conditions of varying NaCI concentration to achieve smaller kf values at a flow rate of I mL/min and at a temperature of 298 K with (I) 20 mM piperazine buffer, pH 9.6 (2) 20 mM triethanolamine, pH 7.5 (3) bistris buffer, pH 6.5 and (4), 20 mM piperazine buffer, pH 5.5, as the eluents. Data selected from Ref. 542. 

FIGURE 36 Experimental data and theoretically generated concentration curves for the adsorption of HAS to a weak anion exchange sorbent DEAE-Sepharose FF at two different protein concentrations. As is evident from the data shown in this figure, the BAMcomb model used in this case predicted a slower adsorption rate during the earlier stages of the adsorption process when higher protein concentrations were employed. 

Pellicular anion-exchange sorbents may also consist of quaternized latex hydrophobically coated onto the surface of an unsulfonated polystyrene solid core. However, using hydro-organic mobile phases can easily wash off the latex particles held onto the particle surface by hydrophobic interactions. 

Chicz, R.M. Shi, Z. Regnier, F.E. Preparation and evaluation of inorganic anion-exchange sorbents not based on silica. J. Chromatogr. 1986, 359, 121-130. 

Figure 6.2. Examples of weak cation- and anion-exchange sorbents.

The ion, whose sign is the same as the ion exchanger (i.e., cations in an anion-exchange sorbent), is excluded much more than the ion that is exchanged (in this case the anion). 

Additives to diet cola—caffeine, saccharin, and sodium benzoate—represent several different classes of compounds that may be extracted on anion-exchange sorbents simultaneously. Caffeine and saccharin are neutral compounds and sodium benzoate is an organic anion (Fig. 6.14). Caffeine and saccharin sorb by van der Waals interaction on the silica-bonded ion-exchange sorbent and the sodium benzoate by anion exchange. The sorbent chosen is a strong anion exchange in chloride form. The sorbent is first cleaned and... 

The high affinity of Pd-chloro-complexes to strong anion exchange materials enables the use of various anion exchange sorbents for preconcentration of Pd with simultaneous elimination of cationic interferents. Especially styrene or acrylic polymers cross-linked with divinylbenezene can be applied for enrichment of PGE from large sample volumes (Matsubara et al. 2000 Kovacheva and Djingova 2002 Lesniewska et al. 2006). 

Propyl sulfonic acid -CH2.CH2.CH2 Si-O-Si-C Weak anion exchange sorbent Can be used with weaker cations Can be used with biological and other aqueous samples... 

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