Particle size in preparative columns

[DJ]

One typically operates under "overloaded" conditions in semi/preparative chromatography. There is a point (mass load) beyond which the gain in resolution provided by smaller particles is lost. Correct?

Besides back pressure, what are the practical differences between a 22 x 150 mm column packed with 3, 5, 10, or 20 micron resin?

[Gerhard Kratz]

Hi DJ,

first question - yes, you are right. In principal it is recommended to run on an analytical column the separation and increase the concentration up to the overload, or break through.

If you keep column dimensions the same and reduce particle size from 10µm to 5 µm back pressure will be double.

To increase the column load with product you can increase ID of the column, reduce length and particle size and you can operate even with 3µm particles.

[HPLCaddict]

If you keep column dimensions the same and reduce particle size from 10µm to 5 µm back pressure will be double.

Unfortunately, it will increase even four-fold.

[DJ]

For instance, Waters offers < 3 micron material in 22 mm ID format.

At what point (in an over-loaded run) is the advantage gained in resolution by the small particle "drowned out"