Binding of s-triazines to dissolved humic substances: Electrophoretic approaches using Affinity Capillary Electrophoresis (ACE) and Micellar Electrokinetic Chromatography (MEKC)

Binding studies were conducted between s-triazines and soil and water extracted fulvic and humic acids (FA and HA) using capillary electrophoretic methods. A first approach to estimate simultaneously the affinity of several s-triazines (hydroxyatrazine, ameline, atraton and ametryn) to dissolved humic substances (HS) was done with the affinity capillary electrophoresis (ACE) modus; the limits of the ACE method resulted in the measurement of the electrophoretic mobility of the pesticide-HS complexes. In a second approach, the partition of the s-triazines between the water and the dissolved humic substances was successfully described like in micellar electrokinetic chromatography (MEKC) using the humic substances as micellar phase. Similar to surfactants, humic acids (HA) behaved like ionic micelles in the aqueous running buffer at concentrations higher than a defined “humic critical micellar concentration” (HCMC). The low molecular weight acidic fulvic acids (FA) behaved the same but showing higher HCMC. These results confirm the micellar properties of HS and the hydrophobic type of interaction of the s-triazines with hydrophobic sites of humic and fulvic ionic micelles.