ONLINE AND OFF-LINE SOLID-LIQUID EXTRACTION AND LIQUID-CHROMATOGRAPHIC ANALYSIS AT TRACE LEVELS, FOR MONITORING OF HERBICIDES AND THEIR DEGRADATION PRODUCTS IN RIVER AND FLUVIO-ESTUARINE FRESH-WATER-SEAWATER INTERFACES

Monitoring of trace levels of phenylurea and chlorotriazine herbicides and their metabolites deisopropylatrazine (DIA) and deethylatrazine ( DEA) was performed on river, estuarine and coastal seawater by off-lin e (n-octadecyl silica, C-18) and on-line (styrene-divinylbenzene copol ymer-based, PRP1) preconcentration techniques using reversed-phase chr omatography and UV and electrochemical detection. It is shown that off -line and on-line technology fit monitoring of trace-level phenylurea and triazine analysis (detection limit 10-50 ng/l) in freshwater as we ll as seawater and in natural water with high dissolved organic carbon (DOC) content. Clean-up was unnecessary for most of the surface water sample for both off-line and one-line techniques. Samples of surface water originating from various rivers (Seine, Charente, Garonne), cana ls (Marennes-Oleron) and estuaries (Charente, Seudre salinity gradient up to 30 parts per thousand) were analysed. Dissolved organic carbon (DOC) contents varied from <1 to 15 mg/l and provided numerous interfe rents and a major 'hump' whose intensity is correlated with the DOC co ntent, suggesting that a major part of the organic matter, namely humi c substances, is retained on the solid phase and eluted as polar compo unds.