# Pore and Film Diffusion and Multicomponent Colloidal Model

**URL:** <https://forum.cadet-web.de/t/pore-and-film-diffusion-and-multicomponent-colloidal-model/1309>\
**Category:** Chromatography Modeling\
**Created:** [September 8, 2025, 2:34pm UTC](https://forum.cadet-web.de/t/pore-and-film-diffusion-and-multicomponent-colloidal-model/1309 "2025-09-08T14:34:48Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![sasha\_onfleek1](https://forum.cadet-web.de/letter_avatar_proxy/v4/letter/s/53a042/32.png) [@sasha\_onfleek1](https://forum.cadet-web.de/u/sasha_onfleek1)\
**Post date:** [September 8, 2025, 2:34pm UTC](https://forum.cadet-web.de/t/pore-and-film-diffusion-and-multicomponent-colloidal-model/1309/1 "2025-09-08T14:34:49Z")

</div>

Hello everyone!

I am fitting my ALC gradient elution data using the Multi Component Colloidal model and the GRM model with success. However I have a question regarding the Pore and Film Diffusion. I’m simulating the elution of 3 different species and I’m using pH dependence. The parameters I am fitting are kinetic\_rate\_constant and logkeq\_ph\_exponent on the isotherm perspective. However, my 3 different species elute very differently from a peak sharpness/ shape perspective and so I also fitted the film and pore diffusion parameters to my data. It looks good and its making quite accurate predicitions. But I question how correct this is, or if there is a better way to regress these parameters. I was wondering if anyone has experience with this and what you recommend I do. I’ve used and Excel that someone has shared on here on how to make estimations of these parameters, but they don’t apply to my situation.

And also more specifically about the Multicomponent Colloidal Model: Should I also introduce the kappa terms and the bpp\_ph\_exponent to the fitting script? I’m not sure I understand 100% what the kappa terms involve, although I’ve already read about them. If someone could help me with this I would appreciate it.

Thanks a lot!