What is selectivity in ion exchange?

What is selectivity in ion exchange?

Ion exchange resins, when placed in a solution, reach an equilibrium state between ions in the solution and ions on the resin. These selectivity coefficients are a measurement of a resins preference for an ion. The greater the selectivity coefficient, the greater the preference for the ion.

What factors affect the selectivity of ion exchangers?

The selectivity series observed in ion chromatography seems to be best explained by the interplay of two components: electrostatic attraction (ES) and the enforced-pairing (EP) that is brought about by hydrophobic attraction and by water-enforced ion pairing.

What is selectivity of resin?

of ion exchange resins. The selectivity coefficient of resins is defined in the ion exchange reactions page. The affinity of the resin for an ion is governed by the size of its hydrated form as well as its charge. The larger the ion, the more the resin bead must expand to accommodate it in the structure.

What is selectivity coefficient?

A selectivity coefficient is the equilibrium constant for the reaction of displacement by one ligand of another ligand in a complex with the substrate. Binding selectivity is of major importance in biochemistry and in chemical separation processes.

What are the factors affecting ion exchange resin?

The factors that affect separation during ion exchange chromatography include the surface area of the stationary phase (resin bead size); the density of exchange sites on the stationary phase surface (cross-linkage); the flow rate of the mobile phase (resin bead size and column geometry; system pressure in high- …

How does ion exchange chromatography increase selectivity?

Ion-exchange chromatography (IEX) emerged as an analytical technique for the separation of ions and ionizable analytes in 1975, when Small et al. described a novel approach to suppress counter ions in the mobile phase prior to conductivity detec- tion [1].

What is exchange capacity of resin?

In general terms, the capacity of an ion exchange resin can be expressed as the quantity of ions that can be taken up by a specific volume of the resin. A measured quantity of caustic (NaOH) is then passed through the resin so as to totally exhaust the resin.

What is resin in ion exchange?

An ion-exchange resin or ion-exchange polymer is a resin or polymer that acts as a medium for ion exchange. It is an insoluble matrix (or support structure) normally in the form of small (0.25–1.43 mm radius) microbeads, usually white or yellowish, fabricated from an organic polymer substrate.

What is selectivity coefficient in ion-selective electrode?

The selectivity coefficient is a numerical measure of how well the membrane can discriminate against the interfering ion. To put this in perspective, if an electrode has equivalent responses to the two ions, then kij = 1.0.

What does a high selectivity coefficient mean?

For reference: Definition of selectivity coefficient Higher concentrations of target ions result in the interfering ions having a smaller effect, and conversely, lower concentrations result in them having a larger effect. An ion selective electrode has its own operable pH range.