Novel Smartphone Paper Sensor for One Health: Monitoring Free Chlorine in Water and Exhaled Breath Condensate

Area of Science:

• Environmental Science
• Analytical Chemistry
• Biotechnology

Background:

• Disinfection is crucial for water safety and hygiene in various settings.
• Conventional chlorine monitoring methods are lab-based and not suitable for decentralized use.
• There is a need for portable, user-friendly chlorine detection methods.

Purpose of the Study:

• To develop a novel paper-based colorimetric biosensing platform for free residual chlorine detection.
• To translate the ISO 7393-2 standard (DPD method) into a portable format.
• To enable rapid, on-site chlorine analysis for environmental and clinical applications.

Main Methods:

• Integration of N,N-diethyl-p-phenylenediamine (DPD) chemistry into a paper-based sensor.
• Development of a reagent-free, portable device for point-of-need chlorine monitoring.
• Utilizing smartphone-based image acquisition for quantitative analysis within 3 minutes.

Main Results:

• The paper-based sensor successfully implemented the ISO 7393-2 standard in a portable format.
• Achieved a detection limit of 12 μM for sodium hypochlorite.
• Validated in real samples (bottled water, exhaled breath condensate) with satisfactory recoveries.
• Demonstrated excellent stability over 30 days at 4 °C and 23 °C, negating the need for refrigeration.

Conclusions:

• The developed paper-based sensor is the first portable implementation of the ISO standard for chlorine detection.
• It offers a user-friendly, rapid, and stable solution for decentralized chlorine monitoring.
• The sensor is suitable for both environmental and clinical matrices, enhancing water safety and hygiene protocols.