Off-line sample preparation by electrophoretic concentration using a micropipette and hydrogel

Area of Science:

• Analytical Chemistry
• Separation Science
• Electrochemistry

Background:

• Traditional sample preparation methods for trace analyte detection can be time-consuming and introduce errors.
• Concentrating analytes is crucial for achieving lower detection limits in complex matrices like environmental water.

Purpose of the Study:

• To develop and demonstrate an off-line electrophoretic sample concentration technique for charged analytes in aqueous samples.
• To evaluate the technique's applicability to various water types (purified, drinking, river) and optimize parameters.

Main Methods:

• An electrophoretic concentration method using a hydrogel-plugged micropipette was employed.
• Charged analytes (anions) were migrated and concentrated from a large sample volume (10 mL) into a small electrolyte volume (20 μL) under an electric field.
• The concentrated analytes were subsequently analyzed using capillary electrophoresis.

Main Results:

• The technique successfully enriched nine different anions, including inorganic ions and organic compounds.
• Achieved limits of detection (LODs) ranged from 1-19 ng/mL for purified water, 4-133 ng/mL for drinking water, and 18-80 ng/mL for river water.
• Demonstrated high linearity (R² of 0.993-1.000) and good repeatability (intraday ≤7.4%, interday ≤14.0%) with concentration factors of one to two orders of magnitude.

Conclusions:

• The developed electrophoretic concentration technique is effective for charged analytes in aqueous samples.
• It offers a simplified sample preparation workflow, eliminating steps like evaporation or reconstitution.
• The method shows promise for improving the sensitivity of analytical techniques for water quality monitoring.