Talanta 53 (2001) 915–925 Photochemical-spectrofluorimetric method for the determination of benzoylurea insecticides: applications in river water samples and in technical formulations M.D. Gil-Garcia a , M. Martı ´nez-Galera a , T. Lo ´ pez-Lo ´ pez a , J.L. Martı ´nez-Vidal a , M.C. Mahedero b, *, F. Salinas b a Department of Analytical Chemistry, Uniersity of Almerı ´a, 04071 Almeria, Spain b Department of Analytical Chemistry, Uniersity of Extremadura, 06071 Badajoz, Spain Received 17 March 2000; received in revised form 17 July 2000; accepted 25 July 2000 Abstract Ultraviolet (UV) irradiation was used to obtain fluorescent photoproducts from four non-fluorescent benzoylurea (BU) insecticides (flufenoxuron (FLF), lufenuron (LUF), hexaflumuron (HF) and triflumuron (TRF)). The effect of solvent, pH (in aqueous solutions), organic solvent percentage and UV irradiation time on the excitation and emission wavelengths and fluorescence intensity were investigated. The largest fluorescence signals and the shortest UV irradiation time were obtained in methanol, ethanol and 2-propanol. Linear calibration graphs were established in the interval between 0.025 and 1.000 g ml -1 from FLF and TRF and between 0.050 and 1.000 g ml -1 from LUF and HF with regression coefficients larger than 0.99. A method based on the use of the first-derivative of the spectra of photoproducts was applied to the determination of BU insecticides in river water samples and in technical formulations. The mean recoveries ranged from 95.0% to 110.0% in river water samples and from 92.0% to 101.0% in technical formulations, according to the compound. A preconcentration step, using LLE, allowed to reach the concentration levels established by the EU directive for pesticides in drinking water. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Photochemically-induced fluorescence; Benzoylurea insecticides; River water; Technical formulations www.elsevier.com/locate/talanta 1. Introduction Benzoylureas (BU) constitutes an important group of pesticides with herbicide or insecticide activity. BU insecticides belong to a class of pesti- cides whose activity is based on the interference with the formation of chitin in the insect’s cuticle, thus blocking the moulting process [1]. Their high selectivity with respect to many non-target insects makes them suitable for inclusion in the inte- grated pest control programs. On the other hand, their rapid degradation in soil and water and the acute low toxicity for animals has encouraged its * Corresponding author. Fax: +34-924-274244. E-mail address: mahedero@unex.es (M.C. Mahedero). 0039-9140/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S0039-9140(00)00528-2