Electrokinetic stacking of electrically neutral analytes with paper-based analytical device

Area of Science:

• Analytical Chemistry
• Microfluidics
• Biotechnology

Background:

• Paper-based analytical devices (PADs) offer low-cost, portable sensing solutions.
• Electrokinetic stacking (ES) is established for enhancing sensitivity of PADs with charged analytes.
• Detecting electrically neutral analytes on PADs remains a challenge for sensitivity improvement.

Purpose of the Study:

• To demonstrate and characterize electrokinetic stacking (ES) for electrically neutral analytes on paper-based analytical devices (PADs).
• To investigate the influence of electroosmotic flow (EOF), electrolyte, and surfactant concentrations on ES performance.
• To evaluate the enhanced sensitivity and potential for semi-quantitative analysis using smartphone-based detection.

Main Methods:

• Development of an ES method utilizing sodium dodecyl sulfate (SDS) micelles to trap neutral analytes.
• Characterization of ES performance using smartphone-based colorimetry and fluorescence detection.
• Optimization of parameters including EOF, background electrolyte concentration, and anionic surfactant concentration.

Main Results:

• Successful demonstration of ES for concentrating electrically neutral analytes (rhodamine B and Sudan III) on PADs.
• Significant enhancement in detection sensitivity: 30-fold for rhodamine B (fluorescence) and 6-fold for Sudan III (colorimetry).
• Achieved a fluorescence detection limit of 50 nM for rhodamine B and a colorimetric detection limit of 5.2 μM for Sudan III.

Conclusions:

• Electrokinetic stacking (ES) is a viable technique for sensitive detection of electrically neutral analytes on PADs.
• The developed method offers rapid, sensitive, and potentially semi-quantitative analysis using simple detection platforms.
• This advancement expands the applicability of PADs for a wider range of analytes.