Page 217 - Vogel's TEXTBOOK OF QUANTITATIVE CHEMICAL ANALYSIS

ACTION OF ION EXCHANCE RESINS 7.2

Table 7.1 Comparable ion exchange materials

TY pe Duolite Rohm & Haas Dow Chemical Bio-Rad Labs
International Ltd Co., USA Co., USA Ltd, Watford, UK
Strong acid Duolite C225 Amberlite 120 Dowex 50 AG5OW
cation Duolite C255 Amberlite 200* AGMP-50*
exchangers Duolite C26C*
Weak acid Duolite C433 Amberlite 84 Bio-Rex 70*
cation Duolite C464* Amberlite 50
exchangers
Strong base Duolite A1 13 Amberlite 400 Dowex 1 AG 1
anion Duolite A1 16 Amberlite 410 Dowex 2 AGMP-1 *
exchangers Duolite A 161 * Amberlite 900*
Weak base Duolite A303 Amberlite 45
anion Duolite A378* Amberlite 68
exchangers Amberlite 93 *
Chelating Duolite ES466* Amberlite 718* Chelex 100
resins
* Macroporous/macroreticular resins.

bonded-phase packings (Chapter 8) with the ion exchange groups being
subsequently introduced into the organic backbone. The small particle size
(5-10pm diameter) and narrow distribution of such packings provide high
column efficiencies and typical applications include high-resolution analysis of
amino acids, peptides, proteins, nucleotides, etc. These silica-based packings are
preferred when column efficiency is the main criterion but, when capacity is the
main requirement, the resin microparticle packings should be selected. The
chromatographic properties of ion exchange packings for analytical separations
have been c~mpared.~~

7.2 ACTION OF ION EXCHANGE RESINS
Cation exchange resins* contain free cations which can be exchanged for cations
in solution (soln).
(Res.A- )B + + C + (soln) e (Res.A - )C + + B + (soln)
If the experimental conditions are such that the equilibrium is completely
displaced from left to right the cation C+ is completely fixed on the cation
exchanger. If the solution contains several cations (C+, D+, and E+) the
exchanger may show different affinities for them, thus making separations
possible. A typical example is the displacement of sodium ions in a sulphonate
resin by calcium ions:
2(Res.SO;)Na+ + Ca2+ (soln) e (Res.SO,); Ca2+ + 2Na+ (soln)

*These will be represented by (Res.A-)B+, where Res. is the basic polymer of the resin, A- is the
anion attached to the polymeric framework, B + is the active or mobile cation: thus a sulphonated
polystyrene resin in the hydrogen form would be written as (Res.SO;)H+. A similar nomenclature
will be employed for anion exchange resins, e.g. (Res. NMe;)Cl-.