96-Well liquid membrane extraction of weakly acidic compounds

Area of Science:

• Analytical Chemistry
• Separation Science
• Sample Preparation

Background:

• Three-phase liquid membrane extraction (LME) is used for acid extraction but faces challenges with high pKa acids.
• Extreme pH conditions or polar organic solvents can compromise stability and chromatographic compatibility.
• Existing methods struggle with efficient extraction of weakly acidic compounds (pK_a > 9-10).

Purpose of the Study:

• To develop an improved three-phase liquid membrane extraction system for weakly acidic analytes.
• To overcome limitations of traditional alkaline acceptors in LME.
• To enhance the applicability and stability of the liquid membrane system.

Main Methods:

• Extraction of nine weakly acidic model analytes (phenols, bisphenols) using commercial 96-well plates.
• Comparison of an alkaline acceptor system with a novel dimethyl sulfoxide (DMSO)-water acceptor system.
• Evaluation of different liquid membranes and study of extraction kinetics.
• Application of both systems to human plasma samples.

Main Results:

• The novel DMSO-water acceptor system overcame limitations of alkaline acceptors, avoiding extreme pH requirements.
• Exhaustive extraction of analytes was achieved in both systems when applied to human plasma.
• The DMSO-water system demonstrated satisfactory analytical performance with high linearity (r² > 0.990) and good precision (RSD ≤ 15%).

Conclusions:

• The developed aqueous-organic-organic system offers a milder approach for liquid membrane extraction.
• This method broadens the scope of extractable neutral species in three-phase systems.
• It provides a viable alternative to established ionization modes for analyzing weakly acidic compounds.