Fluorescein spectrofluorometric quenching detection of chloride and iodide using eight-Blue-LEDs excitation and dual solar cells

This study presents a novel, custom‑built fluorescence detector for the precise determination of chloride and iodide ions based on their quenching effect on fluorescein. The detection system incorporates eight blue LEDs irradiation sources arranged at 0-90° angles relative to twin solar cell detectors connected. Two fluorescence quenching strategies were developed. The injected‑mixture mode (IMFQ) exhibited linear ranges of 0.00-1.00 mM for Cl⁻ and 0.00-1.25 mM for I⁻, with detection limits of 20 µM and 10 µmol L⁻¹, respectively. The continuous‑flow mode (CFFQ) demonstrated superior sensitivity with a dispersion factor of 1.33, wider linear ranges (0.1-6.0 mM for Cl⁻ and 0.05-6.0 mM for I⁻), and lower detection limits (10 µM and 5 µM, respectively). Both strategies rely on Stern‑Volmer kinetics and were successfully applied to real samples (table salts and detergents) with excellent recoveries (95.7-108.1%).