A photo-induced fluorescence (PIF) method was developed for the determination of two benzoyl- and phenylurea pesticides, namely diflubenzuron (DFB) and fenuron (FEN). The photoconversion under UV irradiation of both pesticides into strongly fluorescent photoproducts was performed in several media (methanol, ethanol, acetonitrile, pH4 aqueous solution and pH4 water-methanol (30:70, v/v) mixture). PIF parameters were optimized. Analytical figures of merit for the PIF determination of DFB and FEN were satisfactory, with rather wide linear dynamic range (LDR) values of one to two orders of magnitude, relatively low limit of detection (LOD) values of, respectively, 9-24 ng/mL for DFB and 1-28 ng/mL for FEN, and limit of quantification (LOQ) values of, respectively, 30-80 ng/mL for DFB and 4-95 ng/mL for FEN, according to the medium. Relative standard deviation (RSD) values were in the range 1.7-5.6%. PIF was validated by comparing its analytical performances to those of a standard UV absorption spectrophotometric method. The optimized PIF method was applied to the quantitative analysis of both pesticides in various spiked natural water samples collected in a Senegal agricultural area by the standard addition procedure prior to extraction steps in dichloromethane, with satisfactory mean recovery percentage values (97.0-105.3 for DFB and 98.3-102.8% for FEN). An interference study of foreign species, including pesticides and inorganic ions, likely to be present in natural waters, was also carried out.

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Diflubenzuron (DFB) and fenuron (FEN) are benzoylurea and phenylurea pesticides, widely used in Senegal, that do not exhibit any natural fluorescence, but can be determined by means of photoinduced fluorescence (PIF) methods. Photodegradation of DFB and FEN yielded a number of fluorescent and non-fluorescent photoproducts. For both pesticides, at least 10 photoproducts were detected and identified by gas chromatography-mass spectrometry (GC/MS). To identify the formed fluorescent DFB and FEN photoproducts, their fluorescence spectra were compared with those of standard compounds, including phenol and p-hydroxyaniline. KEYWORDS diflubenzuron and fenuron pesticides, fluorescent photoproducts, gas chromatography-mass spectrometry (GC-MS), photoinduced fluorescence (PIF)

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A new spectrofluorimetric method was developed in this study for simple determination of cadaverine (CD) (1,5-diaminopentane) in flesh of mackerel fish. This method required homogenization of the flesh, solid phase extraction (SPE) with 0.4M HCl/methanol or water/methanol (25/75v/v), centrifugation and derivation with orthophthalaldehyde (OPA). Physico-chemical parameters that affected the sensitivity of the fluorescence signal of the cadaverine-dihydrochloride/orthophthalaldehyde complex (CD/OPA), were optimised; these included reaction time, temperature, solvent system, pH and reactants concentrations (OPA/CD). The study was conducted in acetate buffer (pH 3.5 and 7) and showed low limits of detection (LOD), 0.6 and 25.5 ng. mL -1 respectively. The limits of quantification (LOQ) obtained were 3.5 ngmL -1 (pH 3.5) and 122 ngmL -1 (pH 7). The sensitivity of the results allowed its satisfactory application for quantification of cadaverine in fish.