Fluorescent sensing and selective Pb(II) extraction by a dansylamide ion-exchanger

Area of Science:

• Analytical Chemistry
• Environmental Science
• Materials Science

Background:

• Selective metal ion extraction is crucial for environmental monitoring and remediation.
• Fluorescent sensors offer sensitive detection methods for heavy metals.
• Sulfonamide-based ligands are explored for metal ion complexation.

Purpose of the Study:

• To develop a selective extraction method for lead ions (Pb(II)) from aqueous solutions.
• To investigate the use of a (bis)dansylated sulfonamide as a selective Pb(II) extractant.
• To correlate fluorescence quenching with Pb(II) extraction and complex formation.

Main Methods:

• Selective liquid-liquid extraction of metal ions using (bis)dansylated sulfonamide 1.
• Quantification of metal ion distribution ratios using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
• Monitoring fluorescence quenching of the sulfonamide upon metal ion extraction.

Main Results:

• The (bis)dansylated sulfonamide 1 exhibited high selectivity for Pb(II) extraction over other divalent metal ions (Co(II), Ni(II), Cu(II), Zn(II), Cd(II)).
• Distribution ratios for Pb(II) were 133-1410 times higher than other metals.
• Selective Pb(II) extraction resulted in concentration-dependent fluorescence quenching, confirmed by a non-fluorescent monodansylated control.

Conclusions:

• The (bis)dansylated sulfonamide 1 is an effective and selective extractant for Pb(II) via an ion-exchange mechanism.
• Fluorescence quenching serves as a direct indicator of Pb(II) coordination and extraction.
• The selectivity is attributed to the formation of a stable, low-coordinate binary Pb(II)-sulfonamido complex in the organic phase.