Concentration Enrichment in a Dissolving Microdroplet: Accessing Sub-nanomolar Electroanalysis

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Nanotechnology

Background:

• Traditional concentration enrichment methods require large sample volumes.
• Electrochemistry offers robust probing of attoliter (10^-18 L) volumes.
• Ultramicroelectrodes are key to sensitive electrochemical measurements.

Purpose of the Study:

• To develop a new concentration enrichment strategy using microdroplet dissolution.
• To achieve highly sensitive electrochemical detection at the attoliter scale.
• To demonstrate the quantification of analytes at sub-nanomolar concentrations.

Main Methods:

• Utilizing a microdroplet of 1,2-dichloroethane on a gold ultramicroelectrode (radius ~6.25 μm).
• Employing a microinjector for precise droplet placement.
• Monitoring droplet dissolution optically and electrochemically.
• Measuring the concentration of a redox probe (Cp₂*(Fe)^II) during dissolution.

Main Results:

• Demonstrated robust electrochemical detection down to 800 pM (sub-nanomolar) concentrations of Cp₂*(Fe)^II.
• Achieved voltammetric quantification in the sub-micromolar (sub-μM) regime.
• Showcased the method's potential in a single-blind study for determining unknown concentrations.

Conclusions:

• Microdroplet dissolution on ultramicroelectrodes is an effective concentration enrichment strategy.
• This methodology enables highly sensitive electrochemical quantification at ultra-low volumes.
• The technique holds significant promise for various analytical applications requiring trace-level detection.