Charge amphoteric surface with complexation

An understanding of the chemical behaviour of the element can aid in the choice of appropriate techniques and methods, the application of which would not disrupt the interaction of the element with associated constituents. For example, in the study of aluminium some relevant information may include its amphoteric nature, its ability to form predominantly ionic complexes, its tendency to form hydroxides, and the stability of aluminium complexes formed with biological ligands. It is clear that in order to maintain the ionic interactions the pH, ionic strength and, of lesser importance, the ionic composition of the medium used for sample preparation should be similar to that found in vivo. In addition, highly charged surfaces should not come into contact with the sample. 

Fig. 3 Experimental points of net proton surface excess amounts from the reversible backward titration cycles of sodium montmoril-lonite at different NaCl concentrations. The different lines represent the results of numerical fitting (FITEQL [28]) using the diffuse-double-layer option of the surface complexation model assuming reactions of and Na" ions with permanently charged ion-exchange sites in parallel with protonation/deprotonation reactions on amphoteric edge sites...

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