ONLINE DIALYSIS COLUMN LIQUID-CHROMATOGRAPHY FOR THE DETERMINATION OFPOLAR PESTICIDES IN WATER SAMPLES CONTAINING HUMIC SUBSTANCES

The potential of the on-line combination of dialysis, for the re-oval of interfering humic substances from environmental samples, and trace enrichment on a precolumn packed with C18-bonded silica for the determ ination of polar pesticides by column liquid chromatography with UV de tection is investigated, using six phenylurea herbicides as model comp ounds. The influence of the membrane material, thickness and molecular weight cut-off value, the configuration of the system - i.e. planar o r hollow-fibre membranes - and, especially, the sample volume on analy te recovery and removal of humic substances is studied. Systems which allow the determination of the test compounds at the 1.0 mug/l level i n river and lake water and at the 0.1 mug/l level in tap water are pre sented.