Interactions of hydroxy-s-triazines with sodium dodecyl sulfate-micelles investigated by micellar capillary electrophoresis

The electrophoretic behavior of fourteen 4,6-diamino-s-triazines was invest igated in the presence of an anionic surfactant (sodium dodecyl sulfate, SD S) using micellar capillary electrophoresis (MCE). The measurements were pe rformed at the pH of zero charge of the hydroxytriazines and the existence of strong ionic and H-bond interactions of hydroxy-s-triazine species with the anionic micelles could be shown. Their migration behavior was compared to the n-octanol-water partition coefficients (log K-ow) measured with reve rse-phase HPLC and calculated with different fragment contribution methods. A partition model was proposed to understand the interactions of the three major hydroxy-s-triazine species: cationic, anionic and neutral (presentin g enol and keto forms) with the charged SDS micelles taken as model for cha rged natural polyelectrolytes like humic substances. These results strongly indicate that hydroxy-s-triazines are polarized in the presence of the cha rged micelles and that they are essentially present in their keto form in t he micellar phase (and enol form in the water phase), confirming previous s tudies suggesting the presence of zwitterionic resonance structures at a ne utral pH around their isoelectric point.