Resins & LC Separation Media

Ion Exchange Resins by Type for Strong or Weak Anion or Cation Exchange

We offer a wide range of research-scale separation and purification resins and media from leading manufacturers, including Dow Chemical, Rohm & Haas, Mitsubishi, and Lanxess. In addition to our extensive product offering, we also provide custom media processing and packaging services for many resins to meet unique customer application requirements.

Ion exchange resins are highly ionic, covalently cross-linked, insoluble polyelectrolytes supplied as beads. The beads have either a dense internal structure with no discrete pores (gel resins, also called microporous resins) or a porous, multichannel structure (macroporous or macroreticular resins). They are commonly prepared from styrene and various levels of the cross-linking agent divinyl benzene, which controls the porosity of the particles. Porous beads can be made also by adding homopolystrene, which is soluble in the monomer mixture, and leaching it out later, with toluene, for instance. The PS-DVB precursor beads are post-functionalized to yield the finished resin. Acrylic-based ion exchange resins are also available.

These ionic polymers contain two types of ions: those which are bound within the structure and the oppositely charged counter ions, which are free. The property of ion exchange is a consequence of Donnan exclusion. When the resin is immersed in a medium in which it is insoluble, the counter ions are mobile and can be exchanged for other counter ions from the surrounding medium. Ions of the same type of charge as the bound ions do not have free movement into and out of the polymer.

Ion exchange resins are classified based on the charge on the exchangeable counterion (cation exchanger or anion exchanger) and the ionic strength of the bound ion (strong exchanger or weak exchanger). There are four primary types of ion exchange resins:

1. Strong cation exchange resins contain sulfonic acid groups or the corresponding salts.
2. Weak cation exchange resins contain carboxylic acid groups or the corresponding salts.
3. Strong anion exchange resins contain quaternary ammonium groups. There are two types of strong anion exchange resins:
a) Type I resins contain trialkyl ammonium chloride or hydroxide.
b) Type II resins contain dialkyl 2-hydroxyethyl ammonium chloride or hydroxide.
4. Weak anion exchange resins contain ammonium chloride or hydroxide.

An additional type of ion exchange resin-mixed bed resins-include blends of cation and anion exchange resins.

A resin that contains both an anion and a cation as bound ions is said to be ampholytic. Some ion exchange resins are prepared with chelating properties making them highly selective towards certain ions. In addition to their use in ion exchange, organic polymer supports, many of which are based on PS-DVB resins, are being used as polymeric catalysts in the expanding research area involving heterogenization of homogenous catalysts and as polymeric supports and reagents in combinatorial chemistry.

Learn More
Resin Selection Guide
Inorganic Adsorbents Selection Guide
Custom Resin Processing & Packaging
Custom Packed Columns or Cartridges

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