Direct and reverse micellar-enhanced photo-induced fluorescence determination of fenvalerate in senegalese surface and groundwater

Abstract

Direct micellar-enhanced photo-induced fluorescence (DME-PIF) and reverse micellar-enhanced photo-induced fluorescence (RME-PIF) methods were developed to determine fenvalerate in aqueous medium. The analytical parameters that affect the sensitivity of the DME and RME-PIF methods were optimized. Fenvalerate exhibited a primary excitation and emission band in the 278–317 nm and 325–365 nm regions, respectively. The optimum pH conditions for each medium are as follows: water and Brij-700 (pH = 12), CTAOH (pH = 10), CTAC (pH = 8), SDS (pH = 7). However, the optimal irradiation time varies between 2 and 14 min depending on the solvent. The micellar association constant (Km) of surfactants was determined at different temperatures (298 to 348 K). The Km values increase with temperature, indicating more favorable micellization at higher temperatures. In all cases, a negative value of ΔG° was obtained, indicating that the association reactions of fenvalerate with the surfactants used are spontaneous. Additionally, the RME-PIF method was used to establish the calibration curves of fenvalerate in all micellar media including CTAOH-CH3CN. The linearity of the calibration curves was evaluated by variance analysis (p-value ≤ 5 %), which indicates a significant regression. The RME-PIF method showed significantly enhanced sensitivity with LOD values ranging from 0.006 to 48 ng mL−1. The mixture CTAOH-CH3CN produced the lowest LOD value (0.006 ng mL−1). The SPE procedure yielded satisfactory recovery rates varying between 84.2 and 104.3 % in natural waters. The improved RME-PIF method is better suited for analyzing insecticide residues in environmental matrices due to its analytical interest.