The Foundation of Separation is Preparation-Chromatography
Throughout the development of Science, chromatography is a common method used for analysis and research. Especially in pharmaceutical companies, chromatography is used for separation, identification, and purification of components of mixtures, both qualitatively and quantitatively. It is prominently used in Drug Purification and to trace contaminants.
Chromatography is a biophysical technique to separate different components in a mixture. The molecules travel through the medium, each component may be separated on basis of molecular weight, polarity, size, shape, and binding capacity. Technically there are different types of chromatography namely, Column chromatography, Ion-exchange chromatography, Gel-permeation (molecular sieve) chromatography, Affinity chromatography, Paper chromatography, Thin Layer Chromatography, Gas chromatography, Dye-ligand chromatography, Hydrophobic interaction chromatography, Pseudo affinity chromatography, and High-pressure liquid chromatography (HPLC). On the whole, all types of Chromatographic separation work on the same principle. Among these Column chromatography and Thin Layer Chromatography are performed widely on a commercial scale.
What is Column Chromatography?
Column Chromatography is a method used to isolate single compounds to form a mixture. It is primarily based on differential adsorption to the adsorbent material (e.g. Silica gel and Aluminum oxide). The mixture is stacked into the column filled with adsorbent and a blend of solvents is allowed to pass. This process is also known as a solid-liquid technique.
Before Separation in column chromatography, it is preferred to be optimized first in Thin Layer Chromatography. This can distinctly show the results of how it will perform in column chromatography.
Phases of the Thin Layer Chromatography
There are primarily two phases of Thin Layer Chromatographic separation.
- Stationary phase
The stationary phase is the solid phase. The most common solids used in this phase are silica gel and Aluminium Oxide. Silica gel is more advantageous because of multiple reasons.
- Mobile phase
The mobile phase is liquid. Varied blends of solvents that moves through the column or Thin Layer Chromatography plate. It acts as a developing agent and introduces the mixture into the column.
Now, the Success of the chromatography is based on the selection of the stationary phase. Few things to keep in mind before the preparation of the stationary phase are the Number of components to be separated, affinity difference between the components, and quantity of the adsorbent used.
Silica Gel preparation for TLC
Thin Layer chromatography plate preparation is done by selecting the optimal size of plates for the application of silica gel. The slurry is prepared by mixing silica gel and a little amount of gypsum and water. The slurry is applied on the plate by pouring, dipping, spreading, or spraying method. It is dried and activated by heating in an oven for 30 minutes at 110°C.
Generally, Silica gel is preferred commonly for the stationary phase in Column and Thin Layer Chromatography. Silica gel is an amorphous form of silica (SiO2). It is very porous. It is formed by aggregation of colloidal silica or by polymerization of silicic acid. The aggregate acts as an excellent adsorbent with pore size in the range of 6- 25 nm and great surface area which makes ideal for Thin Layer Chromatography plate preparation.
Here listed are few advantages of silica gel for chromatographic separation.
Advantage of Silica gel
- Silica powder mesh sizes are available a whole range of sizes (30 - 600).
- It offers a good stream rate and best adsorption capacity than any other counterparts.
- It gives a quality result at a cost-effective rate.
- It isolates the components in the blend in a distinct way.
- The Batch and cluster reports are reproducible; hence it is reliable for research and commercial scale.
- Low cost of instrumentation.
Silica Gel has a novel place in the pharmaceutical and food industries. May it is a simple separation of biomolecules or drug purification, Silica gel is an integral component in chromatographic separation.
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