A novel kinetic-spectrophotometry method is developed for the determination of trace amounts of silver nanoparticles (AgNPs) in groundwater samples based on their catalytic effect on the oxidation of indigo carmine by hexacyanoferrate (III) in acetate-acetic acid medium. The absorbance was measured at 612 nm with the fixed-time method. The optimization of the operating conditions regarding concentrations of the reagents and interferences was investigated. The calibration curve is linear over the concentration range 4.0– 300 μg mL−1 of AgNPs with good precision and accuracy. The proposed method is a highly sensitive, selective, and relatively rapid assay of AgNPs at trace level. The method was applied to the determination of AgNPs in groundwater and a synthetic sample.
