Hello,

I´d like to know something about porosity, that i can´t find in any publication i´ve search.
I need to know if in HPLC in reverse phase,the analyte pass through the particle inside a pore or if simply it comes in, and goes out of the pore. Sorry, i hope you to understand me.. I´m not English.

Could anyone tell me where could i read something obout it?
Thanks,
Celia Granda.

The analyte passes through the particle by diffusion. Diffusion is a random process, and the pores inside the particle form a random network. some molecules move inside one pore and move out again, others diffuse inside the pore from one side to the other. Some will leave the pore to go to the one on top, others to the right or the left or the bottom.
There is a good description of the processes in Giddings' Dynamics of Chromatography on page 26ff, if you can get your hands on this book. It is full of equations, but he has done a wonderful job explaining things, so you can often ignore the equations.

A short answer:
Liquid-Phase Separation Terms (Glossary)
Stagnant mobile phase: The fraction of the mobile phase contained within the pores of the particle.
PETER

I am not completely comfortable with the definition from the glossary.
Most LC particles are porous. The particle porosity is defined as the pore volume divided by the particle volume.
There is also the total porosity of the column, which is defined as the elution volume of the unretained peak divided by the empty column volume.
Then there is the interstitial porosity, meaning the space between the particles. This is typically around 40% of the column volume for a standard column packed with spherical particles.

To your second question: the analyte goes through all the space explored by the unretained peak, i.e. the total porosity of the column.

A short description of what is going on within the pores or the interstitial space is given in
J. Chromatographic Science, Vol. 41,April 2003 p. 223-224
PETER