Units in Mass Transfer k_t model - Forum


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TOPIC: Units in Mass Transfer k_t model

Units in Mass Transfer k_t model 19 Oct 2020 18:38 #1

I have a question about the units in the differential equations for the mass transfer model with k_t parameter. Although the units for all quantities are displayed when clicking on the info button, there seems to be something wrong. The left side of the first equation is in M/s while the other terms in that equation and also in the other two equations are in RU/s.
How is this handled when doing a calclulation? Can one translate molar concentrations to RU using the 10e9 factor which appears in the formulas of the k_m model?
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Units in Mass Transfer k_t model 20 Oct 2020 19:42 #2

Hi,
It is something like that.
Since the response is proportional to the molecular weight of the analyte, and, for dextran chips the relation of 1 RU = 1 pg/mm2 is valid. You can convert the response in RU to Molar.
1 RU = 1 pg/mm2 = 10 g/L → g/L divided by Mr (g/mole) → mole/L = M.

Main problem with writing the formula in concentrations (e.g. [LA]) is that we actual mean Response in RU. But this is how most of the formulas are published.

Kind regards
Arnoud

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Last Edit: by Arnoud.

Units in Mass Transfer k_t model 21 Oct 2020 10:52 #3

Thank you for your answer! Yes, that was exactly what confused me. Just using a factor of 10e9 RU/M would have been to simple because it doesn't take the molecule weight of the analyte into account.

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