4-Quinolone-Carboxamide and Carbothioamide Compounds as Fluorescent Sensors. New Fluorimetric Methods for Cu2+ and Fe3+ Determination in Tap Water and Soil

Ion sensor properties of the carboxamide and carbothioamide compounds carrying 4-quinolone group were investigated by means of emission spectrometry in methanol-water (1:1). The compounds were selectively complexed with Cu2+, Pd2+, and Fe3+ among many metal ions. The complex stoichiometry and the stability constant were determined by fluorimetric measurements. The carboxamide compound having phenyl group (QPO) showed sensitivity for Fe3+ ion with a linear range between 0.1 and 0.7 mg/L. The new method was applied in the determination of iron in the spiked tap water samples and the sandy-soil reference material. A modified standard addition method was used to remove the matrix effect. Limit of detection was 0.03 mg/L for the Fe3+ determination method. The carboxamide compound with benzyl group (QBO) showed sensitivity for Cu2+ ion with linear range 0–0.4 mg/L. There was no matrix effect for copper determination in the spiked tap water samples. The detection limit of the method for Cu2+ ion was 0.05 mg/L. The quantification limits of the methods were low enough to determine iron and copper amount in drinking water samples according to EPA.