Chromatography Forum

I made a column to determine the intracrystalline diffusity of a component on an adsorbent. In all articles concerning this topic they plot the first moment µ (mean retention time) vs 1/εv (v=cm/sec, ε=pososity). With me, the line doesn't go through the origin,while in all articles it does. Why is this, doesn't mean i had channeling of the liquid through the adsorbent? Detector signal was not good? Determination of dead volume was wrong?

A couple of thoughts:

1. How are you defining/measuring porosity? If you are using the total porosity of the bed, I would expect a zero intercept. If you are using the porosity of the particles, then I would intuitively expect the intercept to be related to the interstitial volume of your column.

2. How are you defining/measuring dead volume?