Fluorescence Signaling of Zr⁴⁺ by Hydrogen Peroxide Assisted Selective Desulfurization of Thioamide

Thioamide derivative with a pyrene fluorophore was smoothly transformed to its corresponding amide by Zr⁴⁺ ions in the presence of hydrogen peroxide. The transformation was evidenced by ¹H NMR spectroscopy and the signaling was completed within 10 min after sample preparation. Interference from Ag⁺ and Hg²⁺ ions in Zr⁴⁺-selective fluorescence signaling was readily suppressed with the use of Sn²⁺ as a reducing additive. Discrimination of Zr⁴⁺ from closely related hafnium, which is a frequent contaminant in commercial zirconium, was not possible. Prominent Zr⁴⁺-selective turn-on type fluorescence signaling was possible with a detection limit of 4.6 × 10^–6 M in an aqueous 99% ethanol solution.