Not just a background: pH buffers do interact with lanthanide ions-a Europium(III) case study

Area of Science:

• Biochemistry
• Analytical Chemistry
• Inorganic Chemistry

Background:

• Europium(III) is a lanthanide ion with unique luminescent properties.
• Biological and biochemical research often utilizes pH buffers like HEPES, PIPES, MES, MOPS, and TRIS.
• Understanding ion-buffer interactions is crucial for accurate experimental results.

Purpose of the Study:

• To investigate the interaction between Europium(III) ions and common pH buffers.
• To determine the binding affinity and interaction sites of Eu(III) with Good's buffers and TRIS.
• To provide recommendations for buffer selection in lanthanide-based studies.

Main Methods:

• Solution Nuclear Magnetic Resonance spectroscopy (NMR)
• Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS)
• Determination of complex stability constants

Main Results:

• Good's buffers (HEPES, PIPES, MES, MOPS) show significant interaction with Eu(III).
• Interaction sites involve morpholine and piperazine nitrogen atoms in Good's buffers.
• TRIS buffer exhibits negligible affinity for Eu(III) ions.

Conclusions:

• Good's buffers interfere with Eu(III) ions, affecting experimental outcomes.
• TRIS buffer is the preferred choice for studies involving Eu(III) and other lanthanides.
• Buffer selection is critical to avoid artifacts in lanthanide spectroscopy and assays.