# Affinity chromatography in CADET-Process

**URL:** <https://forum.cadet-web.de/t/affinity-chromatography-in-cadet-process/1000>\
**Category:** Chromatography Modeling\
**Created:** [July 22, 2024, 2:56pm UTC](https://forum.cadet-web.de/t/affinity-chromatography-in-cadet-process/1000 "2024-07-22T14:56:31Z")\
**Posts on this page:** 1\
**Showing post:** 15

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**Author:** ![alters](https://forum.cadet-web.de/user_avatar/forum.cadet-web.de/alters/32/294_2.png) [@alters](https://forum.cadet-web.de/u/alters)\
**Post date:** [August 31, 2025, 5:54pm UTC](https://forum.cadet-web.de/t/affinity-chromatography-in-cadet-process/1000/15 "2025-08-31T17:54:23Z")

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What you are calling k\_{eq} is the kinetic rate constant k\_{kin}, which you can fix at 1e8 and not fit this parameter. What are the values of lnKe and Bpp you are using? Also your values for mass transfer params are unrealistic. k\_{film} and D\_p should be on the order of 1e-4 and 1e-10 for pH, respectively, then 1e-5 and 1e-12 for mAb. I would recommend you take a look at my post on transport parameters estimation (below). Also, if you want to achieve a better fit to the front of the BT curve, it is recommended to fit D\_p or obtain D\_p from correlation and fit D\_s (this is more physically consistent but also complicates things).

I also noticed the values for your porosities are very strange. Where are you getting these values? It actually matters a lot because it changes how the phase ratio is defined and significantly affects model parameter estimation.

[Spreadsheet for Calculating Transport Parameters](https://forum.cadet-web.de/t/spreadsheet-for-calculating-transport-parameters/1214)

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