High-Sensitivity Sensor for Palladium Detection in Organic Solvent

A tandem UV-Vis and fluorescence spectroscopy method was developed for the detection of Pd(II) ions in ethanol. The formation of a complex between Pd(II) ions and tropaeolin OO (TR OO) is accompanied by a change in the color of the solution and evolution of the characteristic UV-Vis as well as fluorescence spectra. The optimal detection conditions were achieved at a 3:1 (mL/mL) volume ratio of Pd(II) to TR OO, at 50 °C. UV-Vis spectroscopy enabled the detection of complex formation process over time, while fluorescence spectroscopy allowed a rapid response within 10 min. The limit of detection (LOD) of Pd(II) ions using UV-Vis spectrophotometry was 10 μmol/dm³ at 535 nm. For spectrofluorimetric detection, the LOD was 10 μmol/dm³, with an emission signal observed at 630 nm after 10 min. The kinetics studies showed a stepwise complex formation pathway, supported by DFT calculations. The performance of the method was verified in the presence of interfering metal ions, including Li(I), Na(I), Al(III), Ni(II), Mg(II), Ca(II), Co(II), and Zn(II), confirming its applicability in complex matrices. This approach provides efficient palladium determination in organic solvents, contributing to sustainable practices in metal recycling.