Chromatography Forum

Hello,
My question relates to the size of the particles and the size of the pores of the particles of the column hplc (before and after bonding). I would like to know which is the impact of the size of the particles and/or the pores of the particles on an analysis. I would like to also know if there is a relationship between the size of the particles and the size of the pores of the particles. Lastly, I would like to know if there is information available on this subject on WEB .
Thanks.

To a good first approximation, the particle size affects primarily the efficiency (band broadening) in the column and has little effect on retention or selectivity. Pore size affects primarily retention and selectivity, with a weaker effect on efficiency (primarily for large molecules).

I don't mean to sound patronizing, but if you don't understand what I mean by "efficiency", "retention", and "selectivity", check out some of the on-line courses referenced here for more background information:
http://www.lcresources.com/wiki/index.p ... Q:MoreInfo

There have been number of discussions of particle size effects here on the Forum. Click on the "Search" button (near the upper left cornere of your screen, just under the Chromatography Forum logo). Use "particle size" as the search term, and then get a cup of coffee and settle in for a lot of reading.

For the majority of packings, the pore size is independent of the particle size (typical pore sizes might be 10-30 nm, a typical particle size might be 2 - 10 μm). Pore sizes are specified for the silica substrate before bonding. In the case of something like a C18 column, the bonded phase could conceivably fill a substantial fraction of something like a 10nm pore.

The pore size is inversely related to the specific surface area of the packing (usually expressed in m^2/g). Larger-pore materials have less surface area, hence provide less retention and (usually) different selectivity compared to smaller-pore materials.