Enhanced sample pre-concentration by ion concentration polarization on a paraffin coated converging microfluidic...

Area of Science:

• Analytical Chemistry
• Materials Science
• Microfluidics

Background:

• Microfluidic paper-based analytical devices (μPADs) offer a low-cost alternative to traditional analytical methods.
• Limited sensitivity of conventional μPADs restricts their application scope.
• Ion concentration polarization (ICP) is a promising technique to enhance analyte preconcentration in μPADs.

Purpose of the Study:

• To develop a novel μPAD implementing ICP for improved analyte preconcentration.
• To investigate the efficacy of an off-shelf Nafion® membrane for ICP in μPADs.
• To analyze the impact of sample evaporation on preconcentration efficiency and reduce fabrication costs.

Main Methods:

• Fabrication of μPADs with a straight-to-circular channel geometry using a Nafion® membrane.
• Encasing the device with paraffin films to minimize electro-osmotic flow.
• Applying a DC electric field to induce ICP for analyte preconcentration.
• Evaluating preconcentration factors and the effect of sample evaporation.

Main Results:

• Achieved a maximum concentration factor exceeding 2000-fold for fluorescein sodium salt.
• Demonstrated the influence of sample solution evaporation on the preconcentration factor.
• Reduced fabrication cost to approximately $0.3 USD per device.

Conclusions:

• The developed ICP-μPAD effectively enhances analyte preconcentration, overcoming sensitivity limitations.
• The low-cost fabrication and high concentration factor show potential for diagnostic and environmental monitoring applications.
• The use of readily available Nafion® membranes simplifies device construction.