Determination of phenoxy acid herbicides frm aqueous samples by improved clean-up on polymeric precolumns at high pH.

An improved procedure for the determination of phenoxy acid herbicides in environmental water samples is reported. The procedure consists in solid-phase extraction (SPE) of 60 ml water samples on a polymeric pre-column at pH 2.8, a clean-up step at high pH and subsequent desorption and ion-pair LC separation at pH 8.8. The main improvements are in the basic clean-up step and in the LC eluent composition. The release of compounds which are electrostatically bound to the precolumn is favoured by a washing step with 0.1 mol