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Size Exclusion Chromatography (SEC) is the separation technique used primarily for analytical assays and semi-preparative purification. In this method molecules in solution are separated by their size and by molecular weight. Tosoh Corporation (Toyo Soda) was the first company to introduce its first SEC columns in 1973. The basic principle of Size Exclusion Chromatography is given as below.

Principle of Size Exclusion Chromatography

In this technique the stationary phase is polymeric substance containing numerous pares of molecular dimensions. The mobile phase containing analytes as solvated molecules are separated according to their size, by their ability to penetrate a sieve like structure ( the stationary phase) Larger molecules that will not fit into the pores remain in the mobile phase and are not retained.

This method is mostly suited to separation of mixtures in which the solvents very considerably in molecular size. The mobile phase in this type may be either liq. or gaseous. This tech is mostly used for preparative separation of Micro molecules of biological origin as well as for the purification of synthetic organic polymers.

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