I am studying the extraction thermodinynamics of Am(III) and Eu(III) for two different extracting systems.

In the first case, I have a lipophilic extractant for the selective trivalent An extraction dissolved in kerosene/1-octanol mixture. Both ligand and nitrate concentrations are higher compared to that of metals, therefore the simplified formula to calculate Kex can be used (Kex = D/cost, cost = [NO3-]3 x [L]x, x = complex stoichiometry found by slope analysis). To obtain the thermodynamics parameters (ΔH and ΔS) I must plot Ln(Kex) vs. 1/T.

I am wondering if I must perform slope analyses at different temperatures to obtain the “x” to be used in the formula to calculate the extraction constants (Kex) at different temperatures. In several articles it seems that the authors calculate just one complex stoichiometry (at one temperature), and they use it in the whole range of temperature considered.

The second system I am studying is a hydrophilic complexing agent for the selective An stripping from a loaded organic phase containing a lipophilic extractant. Do you think that in this case, 2 extractants present at the same time, such simplified method is still applicable?

Thanks in advance for any help you can give me