Ultraviolet Photo-Induced Fluorescence Followed by Laser Excitation (UV-PIF-LE) for the Determination of Pesticides in Natural Waters

Abstract

A new method was developed for determining trace amounts of pesticides, using an ultraviolet (UV) lamp to obtain photo-induced fluorescent (PIF) compounds, and then using laser excitation (LE) by a tunable source to excite and simultaneously characterize their fluorescence over a short acquisition time using an intensified charge-coupled device camera. This new UV-PIF-LE method was applied to determine isoproturon, oxadiazon, and fipronil in natural waters. This approach represents an improvement on the previously published direct laser photo-induced fluorescent (DL-PIF) approach that utilized the inclusion of a supplementary UV irradiation device in the experimental setup, permitting the separation of the formation and detection steps for the PIF analytes. This evolution improves the selectivity and increases the sensitivity while maintaining a short analysis time. The UV-PIF-LE method gave very good results with satisfactory analytical performance for the determination of the selected pesticides. This approach also demonstrated good reproducibility, with relative square deviation values between 3.3% and 6.3%, for spiked river water and seawater samples with detection limits in the ng mL⁻¹ range.

Keywords:

• Fipronil
• isoproturon
• laser excitation
• oxadiazon
• pesticides
• photo-induced fluorescence

Additional information

Funding

We thank the Service of Cooperation and Cultural Action of the French Embassy in Senegal for J.P. Bakhoum Ph.D. grant financial support.