Electromembrane extraction using stabilized constant d.c. electric current--a simple tool for improvement of...

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Electromembrane extraction (EME) is a sample preparation technique.
• Traditional EME often uses constant voltage, which can lead to instability.
• Improving the repeatability and stability of EME is crucial for reliable analysis.

Purpose of the Study:

• To present an experimental approach for enhancing analytical performance in EME.
• To investigate the use of stabilized constant direct current (d.c.) electric current in EME.
• To compare the performance of EME at constant current versus constant voltage.

Main Methods:

• Developed an EME method utilizing a high voltage power supply for stabilized constant d.c. electric current (down to 1μA).
• Employed current-controlled ion transfer through a supported liquid membrane (SLM).
• Applied the method to EME-capillary electrophoresis (EME-CE) analyses of basic drugs and amino acids in various matrices.

Main Results:

• Achieved significantly improved repeatability for EME at constant electric current compared to constant voltage.
• Demonstrated a two-fold improvement in relative standard deviation (RSD) for EME-CE analyses (2.8-8.9% vs. 3.6-17.8%).
• Observed no statistically significant differences in detection limits, linear ranges, or correlation coefficients between the two EME modes.
• Eliminated SLM instabilities commonly seen with EME at constant voltage.

Conclusions:

• Stabilized constant d.c. electric current offers superior repeatability for EME.
• The current-controlled EME approach enhances the reliability of EME-CE for analyzing drugs and amino acids in complex samples.
• This method provides a more stable and reproducible alternative to voltage-controlled EME.