Determination of benzoylureas in ground water samples by fully automated on-line pre-concentration and liquid chromatography-fluorescence detection

An on-line pre-concentration method for the analysis of five benzoylureas (diflubenzuron, triflumuron, hexaflumuron, lufenuron and flufenoxuron) in ground water samples was evaluated using two C Is columns, and fluorescence detection after photochemical induced fluorescence (PIF) post-column derivatization. The trace enrichment was carried out with 35 mL of ground water modified with 15 mL of MeOH on a 50 turn x 4.6 turn I.D. first enrichment column (C-1) packed with 5 mu m Hypersil Elite C-18. Retention properties of pesticides and humic acids usually contained in ground water were studied on C-I at concentration levels ranging between 0.04 and 14.00 mu g/L in water samples. The results obtained in this study show that the pesticides are pre-concentrated in the first short column while the humic acids contained in the ground water samples are cluted to waste. Pesticides recoveries ranged between 92.3 and 109.5%. The methodology proposed was used to determine benzoylureas in ground water samples at levels lower than 0.1 mu g/L (maximum levels established by the European Union). (c) 2005 Elsevier B.V. All rights reserved.