Determination of atrazine, its degradation products and metolachlor in runoff water and sediments using solid-phase extraction

In order to determine the fate of the herbicides atrazine (as well as some of its degradation products) and metolachlor in water and sediments, a method was developed to extract and analyse these compounds. The two matrices were separated completely by centrifugation followed by filtration using nylon filters (0.45 mum). Sediments were extracted with a mixture of methanol-0.1N hydrochloric acid (50:50, v/v) using a wrist-action shaker. Filtered water and extracts of sediments were adjusted to pH 4, then concentrated and purified onto two solid-phase extraction cartridges using in tandem C(18) bonded phase column atop sulfonic acid bonded column (SCX). Atrazine, deethylatrazine, deisopropylatrazine and metolachlor retained by the C(18) column were eluted with ethyl acetate. Chlorodiaminotriazine and hydroxyatrazine retained by the SCX column were eluted with a 50:50 (v/v) acetonitrile-0.1M Na(2) HPO(4) aqueous solution (pH 8.5). The extracts were quantified by high performance liquid chromatography with diode array detector (HPLC-DAD) and by gas chromatography with nitrogen-phosphorus detector (GC-NPD). Overall percent recoveries were about 75% and detection limits were between 0.05 and 0.15 microg/l., and 0.5 and 1.5 microg/kg for water and sediments, respectively.