An anion exchanger based on MFE-Polymer (hydroxy-ethylmethacrylate, HEMA) containing quaternary ammonium functional groups has been used to pack a 150 × 4.6 mm id steel column, and the efficiency of this ion exchanger to preconcentrate phenoxy acid herbicides residues has been studied. The phenoxy acid herbicides studied were 2,4-dichlorophenoxy acetic acid (2,4-D), 4-(2,4-dichlorophenoxy)-butanoic acid (2,4-DB), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T), 2-(2,4,5-trichlorophenoxy)-propanoic acid (2,4,5-TP), and 4-chloro-2-methylphenoxy acetic acid (MCPA). Dicamba (3,6-dichloro-2-methoxybenzoic acid), a benzoic acid herbicide usually used in technical products in mixtures with some of the related phenoxy acids, has also been included in the study. Retention of these herbicides on the referred ion exchanger is possible in aqueous acidic medium, probably because of the high polarizing power of the quaternary ammonium groups over the studied herbicides.