INFLUENCE OF DISSOLVED HUMIC MATERIAL AND IONIC-STRENGTH ON C8 EXTRACTION OF PESTICIDES FROM WATER

A mixture of twelve intermediate polarity pesticides, mostly carbamate -type, have been chromatographied on an octadecyl-silica bonded-phase column using acetonitrile-water gradient mobile phase and UV detection . Pesticides were extracted from aqueous matrix by solid-phase extract ion. The extraction system consisted of a glass microcolumn containing octyl-silica solid-phase conditioned with methanol and water. The elu tion was by acetonitrile-dichloromethane (50:50). Studies of extractio n factors like volume of sample, addition of 10 % sodium chloride and presence of dissolved humic material are investigated. After extractio n optimization, it was applied to waters from Lake La Albufera (Valenc ia, Spain). Some pesticides used in rice crops were found at concentra tions above those allowed by the EEC for natural waters (1-3 mu g L(-1 )).