Question

Why are gas chromatographic stationary phases often bonded and cross-linked? What do these terms mean?

Short answer

To provide a long-lasting stationary phase

Step-by-step solution

Introduction

The commercial columns have bonded or cross-linked stationary phases. Their purpose is to provide a long-lasting stationary phase that is not disrupted during temperature programming.

Step 2: 

In bonding, a monomolecular layer of silica is attached to the silica surface of the column by some chemical reactions.

Cross-linking is performed in situ. The column is coated with a layer of polymers. In cross-linking, the peroxide is incorporated into the original solution. As the film is heated, the reaction between the methyl groups is initiated by the free radical mechanism. The polymers get cross-linked through carbon-carbon bonds that result in greater thermal stability of the film.