On-line and off-line solid-liquid extraction and liquid chromatographic analysis at trace levels, for monitoring of herbicides and their degradation products in river and fluvioestuarine freshwater-seawater interfaces

Abstract

Monitoring of trace levels of phenylurea and chlorotriazine herbicides and their metabolites deispropylatrazine (DIA) and deethylatrazine (DEA) was performed on river, estuarine and coastal seawater by off-line ( n-octadecyl silica, C 18) and on-line (styrene-divinylbenzene copolymer-based, PRP1) preconcentration techniques using reversed-phase chromatography 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 well 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 on-line techniques. Samples of surface water originating from various rivers (Seine, Charente, Garonne), canals (Marennes-Oléron) and estuaries (Charente, Seudre salinity gradient up to 30‰) were analysed. Dissolved organic carbon (DOC) contents varied from <1 to 15 mg/1 and provided numerous interferents and a major ‘hump’ whose intensity is correlated with DOC content, suggesting that a major part of the organic matter, namely humic substances, is retained on the solid phase and eluted as polar compounds.