ION-EXCHANGE CHROMATOGRAPHY

Chromatography is a kind of separation technique and is used when a component is required to be purified from a mixture of components. There are various types of Liquid Chromatographs; Ion-exchange chromatography is one of the important among them, here the purification of components is done on an Ion basis, thus it is termed as Ion-exchange chromatography. It is also used for inorganic cations like Sodium, Potassium, etc as well as inorganic anions like Chloride, Sulfate, etc. It has a long history of discovery, dating back to the 1850s. However, in the year 1975 Hamish Small, Timothy S. Stevens, and William C. Bauman, introduced Ion-exchange chromatography in modern form.

INSTRUMENTATION 

Instrumentations that are required during ion-exchange chromatography are:

1. Pump- It is also known as an IC pump and helps in enabling the flow of eluent constant and continuously through the IC column, injector and detector. 
2. Injector- Introduction of the sample can be obtained in numerous ways. Mostly it is done by using injection value. The possibility of the injection of the liquid sample which the injector would provide should be between the ranges of 0.1 to 100 ml of volume, under high pressure along with high reproducibility. 
3. Columns – The smooth flow of Ion-exchange chromatography is based on the columns, the length of the column should be around 3cm to 50cm depending upon its purpose and the diameter should be between 2mm to 5cm. The material might vary from glass, stainless steel, inert plastic, or glass. 
4. Suppressor- It helps in the reduction of chemical background conductivity, which is generally used to elute samples from the column, thus helping in the improvement of the conductivity measurement of the ions. They convert the ionic eluent to water. 
5. Detectors- The process of Ion-exchange chromatography is based on an Electrical Conductivity detector.
6. Data system- Pre-programmer computing integrators are generally used. At certain times more intelligent devices are used.

PRINCIPLES 

 As we already know that the technique of Ion-exchange chromatography is mostly done to separate charged biomolecules. The charged molecules are in the crude sample, which is used as the liquid phase. To the oppositely charged site, the molecules get bind generally, when the liquid is made to pass through the chromatographic column in the stationary phase. 

With the help of solutions of varying ionic strength, the molecules which were previously been separated based on their charge ie, either positive or negative are eluted. Highly selective separation of molecules based on their positive or negative charge occurs when the

the solution is passed through the column. 

APPLICATION OF ION-EXCHANGE CHROMATOGRAPHY

There are various applications of ion-exchange chromatography; some of the typical applications are listed below:

• Demineralization or purification of water: A lot of dissolved salt of Calcium, Magnesium, etc are present in the water. This process is used to remove all the unwanted and harmful Cations and Anions. The water is first passed through Cation Exchanger, which replaces the Cation with an H+ ion. In the second part, through the Anion Exchanger, the water is passed, which helps in the replacement of Anions present in the water with OH- ions. Thus purifying the water. 
• Separating Amino Acids: Separations of Amino Acid are done through Ion-exchange chromatography is based on the charges. In the first step preparation of charged resin beads column is required. In the second step through the column, the amino acid mixture is run and by lowering the pH, the amino acid is made stuck to the column. In the third step, the salt concentration is increased and the amino acids are knocked off the column. Asp, Ser, and Lys will elute serially. As they elute off the column, fractions of set volume are collected and analyzed, and an elution profile is created.
•  The application of ion-exchange chromatography is super beneficial in not only analyzing lunar rocks but also rare trace Earth’s elements. 
• Ion-exchange chromatography is also used in analyzing hydrolysis’s product of nucleic acid. Details are obtained about the molecular structures and their related biological functions as hereditary information carriers.
• Hard water softening- Transformation of the hard water by ion-exchange chromatography is based on H+ resin or acid resin which helps in absorption of cation of the salt that is dissolved in hard water. 

MgCl2 + 2H+                       Mg – Resin + 2HCl

CaCO3 + 2H+                     Ca – Resin + H2CO3

CONCLUSION

To summarize the above article, ion-exchange chromatography is one of the greatest inventions of the century in the field of Bioinstrumentation; it has been proven to be super beneficial in today’s modern science. Its application in the drug and pharmaceutical industry to mainly stabilize and improve the solubility of molecular properties of active pharmaceutical drugs has been a game-changer. It not only has a massive contribution in the industrial field but also serves clinical purposes. The simplicity and uncomplicated process of ion-exchange chromatography make it more suitable to be frequently used not only in small laborites but also in industrial places.