Discussion Forum

Hello all,

I am trying to simulate 1D time dependent study of isotachophoresis (a type of electrophoresis) in Comsol. Its a preconcentration technique that allows focusing and separation of analyte ions based on difference in electrophoretic mobility of leading, analyte and trailing ions.

I have compiled my setup in Nernst-Planck Equation interface (under Chemical Species Transport module) as shown in this link - https://www.comsol.com/blogs/exploring-the-4-basic-modes-of-electrophoresis/

In my setup, concentration of my analyte ion is too small [1e-3 mM] compared to concentration of leading and trailing ions [50 mM]. Theory (and experimentally validated) suggest that analyte ion must focus at interface of leading and trailing ion but in my simulation, I do not see any change in concentration of analyte ion, rather I get convergence error. I have noticed that the simulation runs fine when the initial analyte concentration is 1 mM.

I have tried function smoothening to eliminate numerical oscillation and noise, applied mesh refinement at initial leading and trailing ion interface location and played around with consistent and inconsistent stabilization method but the problem persist.

I wonder if I am using the correct interface as Comsol offers two other interfaces (Transport of Diluted Species and Electrophoretic Transport)? I wish to ask what really is the difference among the three interfaces as their description is pretty much the same.

Any suggestions or input will be greatly appreciated. Thanks.

Best Adi