Implementation of a plasticized PVC-based cation-selective optode system into a paper-based analytical device for...

Area of Science:

• Analytical Chemistry
• Materials Science
• Biomedical Engineering

Background:

• Classical cation-exchange optodes are crucial for ion detection.
• Paper-based analytical devices (PADs) offer portable and cost-effective sensing platforms.
• Integrating optodes into PADs presents challenges in stability and sample handling.

Purpose of the Study:

• To implement a cation-exchange optode into a vertically-assembled paper-based analytical device (vPAD).
• To develop a stable and reliable system for colorimetric sodium (Na+) assays.
• To evaluate the performance of the vPAD system compared to conventional optodes.

Main Methods:

• Development of a vertically-assembled PAD (vPAD) incorporating an ion-selective optode (ISO) membrane.
• Inkjet deposition of ionophore-doped PVC membranes onto functionalized paper layers.
• Integration of a pH-buffering function and lamination for device stability.
• Capillary-driven liquid transport for automated pH adjustment and optical detection.

Main Results:

• Demonstrated successful implementation of a cation-exchange optode in a vPAD for sodium detection.
• Achieved stable ion-exchange equilibrium and sigmoidal response curves for Na+ from 10^-5 to 1 M at pH 5.0-7.0.
• Confirmed that whole device lamination prevents sample evaporation and maintains analyte concentration.

Conclusions:

• The vPAD system provides a stable and effective platform for ion-selective optical sensing.
• Cellulosic paper substrate influences optode response, requiring further investigation.
• This approach advances the development of portable and sensitive analytical devices.