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INTRODUCTION

Develop and evaluate a sensitive FIA-PIF method for α-cypermethrin detection in Senegal waters, showcasing analytical performance and applications in natural water samples.

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INTRODUCTION

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  1. Determination of α-Cypermethrin Insecticide Residues In Senegal Waters By A Flow Injection Analysis - Photochemically Induced Fluorescence (FIA-PIF) Method Jean-Jacques Aaron1, Moussa Mbaye1,2, Mame Diabou Gaye Seye1,21 Laboratoire Géomatériaux et Environnement (LGE), Université Paris-Est Marne-la-Vallée, France 2 Laboratoire de Photochimie et d'Analyse, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal

  2. INTRODUCTION • α-cypermethrin: the most widely used pyrethroid insecticide in Sénégal • As a consequence, serious problems of contamination of natural waters by α- cypermethrin • Chromatographic methods applied to the identification and determination of α-cypermethrin and other pesticide residues in natural waters, but several drawbacks (expensive equipment & chemicals; time-consuming optimization and derivation procedures) • Recent development of a sensitive and simplephotochemically-induced fluorescence (PIF) method in stationary solution to transform by UV irradiation non-fluorescent α-cypermethrin into strongly fluorescent photoproduct(s)

  3. GOALS OF THE WORK ✓ Development and optimisation of a PIF method combined with flow injection analysis (FIA-PIF method) for determination of α-cypermethrin, using organic solutions and cyclodextrin (CD) media ✓ Evaluation of the analytical performances of the FIA-PIF method for α-cypermethrin ✓Application of the FIA-PIF method to the quantitative analysis of α-cypermethrin in natural waters collected in Sénégal

  4. α- CYPERMETHRIN STRUCTURES

  5. EXPERIMENTAL ✓ On-line FIA-PIF system: peristaltic pump + injection loop + Knauer photoreactor (low pressure UV lamp) + Kontron SFM-25 spectrofluorimeter + PC ✓ [-cypermethrin] = 40-4170 ng mL-1 in all media under study ✓ CD concentrations: [-CD] = 8x10-3 M; [HP--CD] = 10-2 M ✓ PIF excitation and emission λ = 285 and 333 nm in acetonitrile ; 288 and 318 nm in CD media ✓ Injected volumes: 100-280 L; Flow rate : 0.3-1.8 mL min-1; Reactor length: 100-240 cm; FIA mobile phase: de-ionized water ✓ Analytical applications performed by the direct spiking procedure : tap water and natural water samples collected in Sénégal (Niayes agricultural area) & fortified with 41-416 ng mL-1 of -cypermethrin

  6. RESULTS • Optimization of the FIA parameters Flow rate effect on the FIA-PIF signals✓ Smaller optimal flow rates (maximum PIF-FIA signals) in CD media (0.7 & 0.3 mL min-1 in -CD & HP--CD, respectively) than in acetonitrile, indicating : • Longer exposure time of -cypermethrin in the photoreactor, so that the photoreaction can take place with a larger photoconversion yield in CD media

  7. Flow rate effect on the FIA-PIF signal of -cypermethrin Conditions: 10-5 M α-cypermethrin in 10-2 M HP-β-CD solution, after on-line UV irradiation. Injected volume = 140 µL; photoreactor length = 200 cm

  8. Reactor length effect on the FIA-gram Conditions: 10-5 M α-cypermethrin in 10-2 M HP-β-CD solution, after on-line UV irradiation. Injected volume = 140 µL; flow rate = 0.7 mL min-1 • Well-resolved FIA-PIF peaks • Higher FIA-PIF signal for a reactor length of 200 cm in all media under study

  9. Injection volume effect on the FIA-PIF signal of -cypermethrin Conditions: 10-5 M α-cypermethrin in 8 x10-3 M β-CD solution, after on-line UV irradiation. Flow rate = 0.7 mL min-1; photoreactor length = 200cm • Weak variation of the FIA-PIF intensity with the injection volume in CD media✓Optimal injection volumes = 140 L in β-CD medium and 196 L in acetonitrile and in HP-β-CD

  10. Optimum analytical parameters for the FIA-PIF determination of α-cypermethrin 10-5 M in various media

  11. FIA-PIF analytical performances of α-cypermethrin in different media ✓ Good precision of the calibration curves : “r” close to unity ✓ Good sensitivity of the method FIA-PIF: low LOD values ✓Rather wide concentration LDR: 1 to 2 orders of magnitude ✓ Satisfactory reproducibility : small RSD values

  12. Analytical applications in natural waters ✓Satisfactory recovery values for natural water samples ✓ No significant interference from the background resulting from inorganic and/or organic compounds probably present in the natural water samples under study

  13. C O N C L U S I O NS ✓ Simplicity and low cost of the FIA-PIF method ✓Enhancement of the sensitivity of the FIA-PIF method in HP-β-CD ✓ Higher frequency of samples/hour with the FIA-PIF method than with stationary PIF ✓ Detection of -cypermethrin residues at the ng mL-1 level in spiked tap water and natural waters, using HP-β-CD media ✓ Possible use of FIA-PIF as a routine method for determination of -cypermethrin in polluted surface waters and ground waters.

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