A novel determination method for Ag(I) in environmental samples based on reduction of absorbance and fluorescence quenching of Eosin Y

Abstract

Ag(I) and Eosin Y (EY) can interact directly under weakly acidic conditions to form a sparingly soluble ionic association which results in absorbance reduction and fluorescence quenching of EY. New spectrophotometry and fluorescence quenching methods have been developed for the determination of Ag(I) within the ionic association of EY-Ag, with detection limits of 0.17 µM and 2.2 nM, respectively. The fluorescence quenching method offers high sensitivity, good selectivity, high accuracy, and ease of operation, making it suitable for the analysis of silver ions in surface water samples and wastewater samples as well as Ag(I) standard samples. Through the analysis of the absorption spectrum, density functional theory (DFT) theoretical calculations and Nuclear Magnetic Resonance (NMR) spectroscopy, it was found that under weakly acidic conditions, the Ag(I) coordinates with the carboxyl functional group of EY, forming a 1:1 sparingly soluble ionic association that induces static fluorescence quenching.