Ratiometric fluorescence determination of Gd(III) using plumbagin: method validation and analysis of real samples

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Materials Science

Background:

• Gadolinium (Gd(III)) is a lanthanide with diverse applications.
• Developing sensitive and selective methods for Gd(III) detection is crucial.
• Plumbagin (PLB) is a natural compound with potential as a fluorescent probe.

Purpose of the Study:

• To investigate the spectroscopic interaction between plumbagin and Gd(III).
• To develop a ratiometric fluorescence method for quantitative Gd(III) determination.
• To validate the method for analyzing Gd(III) in real-world samples.

Main Methods:

• UV-vis and fluorescence spectroscopy were employed to study the Gd(III)-PLB interaction.
• A ratiometric fluorescence index (R = I530/I610) was established for quantification.
• Supporting techniques included 1H-NMR, ESI-MS, FT-IR, XPS, and DFT calculations.
• Method optimization involved pH, solvent composition, and excitation wavelength.

Main Results:

• Coordination of Gd(III) with PLB induced spectral changes and dual fluorescence emission at 530 nm and 610 nm.
• The 530 nm emission showed higher sensitivity to Gd(III), forming the basis for the ratiometric index.
• Spectroscopic and computational data confirmed the formation of the [Gd(PLB)3]+ complex.
• The ratiometric method demonstrated enhanced reliability against instrumental and matrix interferences.

Conclusions:

• A novel ratiometric fluorescence strategy for Gd(III) detection was successfully developed.
• The method proved effective for determining Gd(III) in fertilizer samples, showing good agreement with ICP-MS.
• This work highlights the potential of PLB-based ratiometric fluorescence for practical elemental analysis.