Morning, This should be fairly straightforward, at least in model definition. I think it would be easier to have the measurements for each compartment as their own column of data, e,g, c_plasma, c_brain, c_liver. Choose a base model e.g. 2 compartments and then once you have chosen "edit graphical" you can right click in your model to add extra observations and compartments as required.
I would look at the NLME examples guide, to become more familiar with the model building e.g. Graphically create a peripheral elimination model (page 177 in v8.1 documentation)
and also look at some of the recorded PML school webinars e.g.
https://support.cert...onal-antibodies.
Try and that and if you get stuck post the project file back here and we can try to advise further.
Simon.
Edited by Simon Davis, 21 January 2019 - 08:33 AM.