An Ionophore-Based Anion-Selective Optode Printed on Cellulose Paper

Area of Science:

• Analytical Chemistry
• Environmental Science
• Materials Science

Background:

• Traditional anion-selective optodes often rely on hydrophobic polymers and plasticizers, limiting portability and cost-effectiveness.
• Developing portable, low-cost sensing platforms is crucial for widespread environmental monitoring applications.

Purpose of the Study:

• To introduce a general, portable, and cost-effective anion-sensing platform utilizing ion-selective optodes and smartphone detection.
• To demonstrate the platform's capability for selective fluoride detection in drinking water samples.

Main Methods:

• Development of a novel optode based on hydrophilic cellulose paper, inkjet-printed with an anion ionophore and a lipophilic pH indicator.
• Incorporation of a dried buffer onto the cellulose matrix to eliminate sample pH dependence.
• Utilizing a smartphone with a color analysis app for quantitative detection of color changes.

Main Results:

• The new cellulose paper-based optode successfully detected fluoride ions with high selectivity using an Al(III)-porphyrin ionophore.
• The platform demonstrated accurate fluoride measurements in real drinking water samples.
• The sensing mechanism is compatible with both Lewis acid-base and hydrogen bonding recognition principles.

Conclusions:

• The reported anion-sensing platform offers a portable, cost-effective, and user-friendly approach for environmental monitoring.
• The cellulose paper-based optode technology represents a significant advancement over traditional methods, enabling on-site analysis.
• This platform shows promise for the detection of various anions beyond fluoride, applicable in diverse environmental and health-related fields.