Determination of chlorotriazines in aqueous environmental samples at the ng/l level using preconcentration with a cation exchanger and on-line high-performance liquid chromatography

Abstract

On-line precolumn sample handling was applied to preconcentrate chlorotriazines in aqueous samples prior to their high-performance liquid chromatographic separation. Chlorotriazines are ionizable compounds (p K a between 1.6 and 2) and a strong cation exchanger is used for their concentration. As the direct percolation of large aqueous sample volumes through a cation-exchange precolumn is impossible owing to the high concentrations of inorganic cations in natural waters, a two-step preconcentration has to be carried out. First, triazines are trapped in their neutral form by direct percolation of the aqueous sample through a first precolumn packed with the copolymer-based PRP-1 sorbent. In the second step, the PRP-1 precolumn is coupled to a second precolumn packed with a cation exchanger. A small volume of deionized water—acetonitrile mixture at pH 1 allows the triazines to be desorbed from the PRP-1 precolumn and concentrated on the cation exchange precolumn in their protonated form. The content of the cation exchange precolumn is analysed on-line using an acetonitrile—water gradient. As the PRP-1 precolumn also acts as a powerful filter to many neutral interferents, detection limits are below the 10 ng/l level in drinking water.