Ion Exchange Chromatography,Defination, principle and advantages disadvantages.

Table of Contents

Ion exchange chromatography is a technique that allows the separation of ions and polar molecules based on their affinity to the ion exchanger. It can be used for different charged molecules including large proteins, small nucleotides, and amino acids.

This method of separation is based on the use of ion-exchange resins as packing materials in a glass column. The ion exchange resin is a cross-linked organic polymer of styrene-divinylbenzene and some polar groups at intervals that are responsible for the ion exchange properties. The reactive group containing the exchangeable ion determines a resin’s characteristics. The amount of divinylbenzene determines how porous the bead will be.

Ion Exchange Chromatography Resin Types

There are two types of resins based on the group attached to them.

  1. Cation Exchange Resin: These are inert polymeric compounds that contain acidic groups like -SO3H, -COOH, etc. These groups are capable of exchanging H+ ions with the cations present in solutions.
  2. Anion Exchange Resin: These are polymeric compounds that contain basic groups like quaternary ammonium salts{-N+(CH3)3OH}, amines, etc. These are capable of exchanging -OH ions with anions present in the solution.

Types of Ion exchange chromatography

On the basis of the types of resin used, Ion exchange chromatography can be classified into two types.

  1. Cation exchange chromatography: In this type, the stationary phase contains a resin having acidic groups and hence positively charged molecules are exchanged with H+ ions of resin.
  2. Anion exchange chromatography: In this type, the stationary phase contains a resin having basic groups, and hence negatively charged molecules are exchanged with -OH ions of resin

Basic Principle of Ion exchange chromatography(Working of ion exchange chromatography)

The ion-exchange chromatography is based on the principle of exchange affinity of ions present in the mobile phase (solution of mixture) with the resin of the stationary phase. The resin may be cationic or anionic depending on the separation of cations or anions.

When the mobile phase containing a mixture of charged ions or polar molecules is applied to the column containing resin, the interaction between a charged group of resin and charged molecules/ions present in the solution takes place. The -H+ ions and -OH ions of resin are replaced by the ions or molecules of the mixture according to their ion-exchange affinity. Different ions have different capacities to undergo exchange with different ion exchangers. This fact enables the separation of a mixture of ions. Finally, attached ions are separated from the resin using suitable solvents, such a process is called elution.

At low concentration and room temperature, the extent of exchange increases with increasing valency or charge of exchanging ions. For example: Na+<Ca2+<Al3+<Th4+

At low concentration and room temperature, if ions have constant valency then the extent of exchange increases with an increasing atomic number of exchanging ions. For example Li+<Na+<K+

The relative exchange capacity of different ions depends on their value of activity coefficients. The greater the value of the activity coefficient, the greater is the exchange capacity. Moreover, the exchange capacity of -H+ ion and -OH ion varies with the nature of the functional group. The stronger the acid and base, the lower is the exchange capacity of the resin.

Ion Exchange chromatography Experiment

The ion-exchange chromatography uses the column method. Generally, a glass column Is used as support for the stationary phase. The resin which is being used as a stationary phase must have a small particle size. Therefore, it provides a large surface area for the interaction of the solution and the resin.

  1. First of all, the desired resin is dissolved in the distilled water and made slurry and any large particles are removed.
  2. The glass tube is filled with distilled water and all air is displaced so that the air bubble doesn’t interfere experiment. The water is filled to about three- a quarter of the tube. The sintered glass disc can be fitted at the lower end of the tube.
  3. The slurry of fully swollen resin is poured along with the wall of the tube. The setting of the resin is enhanced by gently tapping the tube, but an air bubble should not be developed in the packed column.
  4. The mixture to be separated is applied on the top of the column using water as solvent or buffer of an aqueous solution of suitable pH.
  5. Elution is done by using a salt gradient solution or using a suitable buffer solution.
Apparatus/ procedure / process for ion exchange chromatography

Uses of Ion exchange chromatography

  1. Ion exchange chromatography can be used in softening of hard water.
  2. It is used in the separation of similar ions from one another.
  3. It is used in the removal of interfering ions. For example, phosphate ion is the interfering radical in the estimation of Ca++or Ba++ ions. Phosphate ions can be removed by passing the solution of Ca++or Ba++ ions through a sulphonic acid cation exchanger.
  4. It is suitable for the fractionation of compounds having ionized groups.
  5. In the separation of the lanthanoids and also of other cations of very similar properties.
  6. In the purification of proteins/ amino acids
  7. In the purification of DNA

Advantages and disadvantages of Ion exchange chromatography

Advantages of ion exchange chromatography

  1. The separation can be altered by changing pH of the buffer, salt gradient, or by changing the nature of ion exchange resin.
  2. This technique has high selectivity because it can separate molecules having small differences in charges
  3. Separation time is short hence large sample volumes can be separated in a short period of time.
  4. It has a low maintenance cost.
  5. Inorganic metal ions can be separated and detected

Disadvantages of Ion exchange chromatography

  1. This technique is only limited to the separation of charged ions or polar molecules.
  2. The resin used in this technique may get damaged by some materials.
  3. It requires a large volume of samples.
  4. The instrument is expensive and requires expensive chemicals such as buffers

Difference between affinity and Ion exchange chromatography

Ion exchange chromatography Affinity chromatography
In ion-exchange chromatography, the separation of ions and polar molecules is based on their affinity to the ion exchanger.In affinity chromatography, the separation of mixture is based on the special affinity of one of the components with the other.
Only charged molecules can be separated.Both charged and uncharged molecules can be separated.
Acidic or basic functional groups of resin act as binding sites.Ligand acts as binding sites.

FAQs

What is ion-exchange chromatography?

Ion exchange chromatography is a technique that allows the separation of ions and polar molecules based on their affinity to the ion exchanger.

What are the types of ion-exchange chromatography?

There are two types of ion-exchange chromatography: cation exchange chromatography and anion exchange chromatography

Ion-exchange chromatography resin types

Cation exchange resin and Anion exchange resin are the two types of ion-exchange chromatography.

What are the differences between affinity and ion-exchange chromatography?

In ion-exchange chromatography, the separation of ions and polar molecules is based on their affinity to the ion exchanger, while the separation of mixture is based on the special affinity of one of the components with the other in ion-exchange chromatography.

Apparatus/ procedure / process for ion exchange chromatography

Share this to:

Leave a Reply

Your email address will not be published. Required fields are marked *