Ionic liquid-based slab optical waveguide sensor for the detection of ammonia in human breath

Area of Science:

• Chemical Sensors
• Optical Sensing
• Analytical Chemistry

Background:

• Gaseous ammonia detection is crucial for environmental monitoring and medical diagnostics.
• Optical waveguide sensors offer high sensitivity for trace gas analysis.
• Ionic liquids and indicator dyes provide a basis for novel sensing materials.

Purpose of the Study:

• To develop and characterize a novel slab optical waveguide sensor for sensitive gaseous ammonia detection.
• To investigate the use of an ionic liquid (trihexyl(tetradecyl)phosphonium chloride) and bromothymol blue (BTB) as the sensing medium.
• To evaluate the sensor's performance, reusability, and applicability to real-world samples like human breath.

Main Methods:

• Fabrication of a slab optical waveguide sensor with an ethyl cellulose-supported ionic liquid film containing bromothymol blue.
• Exposure of the sensor to varying concentrations of gaseous ammonia.
• Measurement of changes in bromothymol blue absorbance due to ammonia diffusion.
• Testing the sensor's response, reproducibility, and reusability.
• Application of the sensor for detecting ammonia in human breath samples.

Main Results:

• The sensor demonstrated fast and reproducible responses to gaseous ammonia.
• Accurate detection of ammonia was achieved in the range of 100-1800 ppb, with a detection limit of 69 ppb.
• The sensor exhibited reversible gas sorption/desorption dynamics, indicating reusability.
• Successful application in determining ammonia content in human breath was achieved.

Conclusions:

• The developed optical waveguide sensor is a sensitive and reusable platform for gaseous ammonia detection.
• The combination of ionic liquids and bromothymol blue in an optical waveguide configuration is effective for trace ammonia analysis.
• The sensor shows promise for non-invasive medical diagnostics and environmental monitoring applications.