Separation of a mixture of hydrophilic and hydrophobic herbicides by ion-interaction reversed-phase HPLC

An ion-interaction reversed-phase chromatographic method is presented for the separation of 2,4-dichlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid, 2,4,5-trichlorophenoxyacetic acid, 4-(2,4-dichlorophenoxy)butyric acid, 4-chloro-o-tolyloxyacetic acid, 4,6-dinitro-o-cresol, and 5-bromo-3-sec-butyl-6-methyluracil. These herbicides, which do not belong to the same functional classes, are characterized by different chemical properties, particularly in terms of hydrophilicity. The effect of mobile phase pH, organic modifier, ion-interaction reagent, and stationary phase packing material on analyte retention is investigated and discussed. The method permits detection at concentration levels less than 12 μg/L without preconcentration or pretreatment steps and is applied to the analysis of river water samples.