Usefulness of cyclodextrin media for the determination of alpha-cypermethrin by photochemically induced fluorescence: analytical applications to natural waters.

The photochemically induced fluorescence (PIF) spectral properties of alpha-cypermethrin in organic solvents (hexane, dichloromethane, acetonitrile, ethanol) and in cyclodextrin aqueous solutions (beta-CD and 2-hydroxypropyl-beta-CD, 2-HP-beta-CD) were investigated. The photolysis kinetics of alpha-cypermethrin were evaluated in the various media. The PIF signal was found to be significantly enhanced in the CD media relative to the organic solvents. The stoichiometry and the formation constants of the alpha-cypermethrin inclusion complexes formed with the CDs were determined. The analytical performances of the PIF method were improved in the presence of HP-beta-CD relative to the other media, and a CD-enhanced PIF analytical method was developed. The limits of detection and limits of quantification ranged, respectively, between 6 and 98 ng/mL and between 24 and 343 ng/mL, depending on the medium. Application to the analysis of tap water and Senegal natural water samples collected close to agricultural areas and spiked with alpha-cypermethrin yielded satisfactory recoveries going from about 77% to 98%. An interference study of foreign species, including pesticides and inorganic ions likely to be present in natural waters, was also carried out.