Diol functionality, size-exclusion

Protein-Pak packings are designed for the size exclusion chromatography of proteins and related compounds. They are based on silica, which is deactivated with glycidylpropylsilane. The diol function prevents the interaction of the target analytes with the silica surface. However, because coverage of the silica surface is always incomplete, residual acidic silanols can interact with the analytes. For this reason, most applications are carried out with a salt concentration above 0.2 mol/liter, which eliminates the interaction of analytes with surface silanols. Protein-Pak packings are stable from pH 2 to pH 8. 

There is a wide diversity of available trade names, synthetic nuances, or geometric ones such as column size and shape. However, over three-fourths of HPLC is done with chromatographic columns prepared as porous silica derivatives with bonded alkyl functional groups. Other bonded groups that are noteworthy include diol functionality for aqueous size exclusion and bonded counterions for ion-exchange. The result is an increasingly well focussed interest in relatively few, but widely used, column types. It is known that nominally identical column types do not exhibit identical separation behavior in practice. This nonuniformity has provoked user interest in the question of the extent to which sorptive reproducibility occurs from column to column and, similarly, among different manufacturers. 

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