duely noted

methoxy-subbed alks lend themselves well to separation, perhaps a solvent partition method would be
more accessible for most nexians.

you can find those values on either chemicalize or chemspider.

i like that graphical interface, it looks familiar

Alright, so I ran the logD values at the pH's where the charges are -1, 0, and +1 for hordinine. pH 6.5, 9.7, 12.5 respectively.

Here are the results:

pH: logD Hordenine logD Gramine
6.5 -0.77 -0.68
9.7 1.65 1.88
12.5 -0.05 2.01

These results would indicate that at pH 12.5 gramine is far more soluble (~100 times) in NP solvents compared to hordenine. This makes sense because the charge of hordenine at pH 12.5 is -1 and the charge of gramine at pH 12.5 is 0. Obviously this is an estimate and doesn't apply to all NP solvents but I think it would be worth a try to separate before performing IEX. Hope this helps.

Are all of those values found on chemicalize or chemspider? I thought they only put out literature values, not predicted values. Not sure though to be honest.

Looks like you can't specify the pH for the logD values on chemicalize or chemspider. With just a quick look. Also, I can change the ionic strength of the solution with the software I have. Varying the concentrations of Cl- and Na+ ions.

Would you mind sharing the name of the software you are using?

Good to have you here

looks like Marvin Beans, particularly Sketch. it has pKa/pI calculation functions.

Yup, that was marvin sketch with the calculator plugins (I have an academic license).

Oh cool, I actually have that on an old computer, courtesy of some pointers from benz...minus the calculator of course

I've never had time to sit down and really dive into it. Glad there are people with much better working knowledge than I. Looking forward to your collaborations and contributions!