Label- and Reagent-Free Optical Sensor for Absorption-Based Detection of Urea Concentration in Water Solutions.

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Sensor Technology

Background:

• Accurate urea detection is crucial for chemical, biomedical, industrial, and automotive sectors.
• Existing methods for urea detection can be costly, require reagents, or involve physical contact.

Purpose of the Study:

• To develop a compact, low-cost, reagent-free, and contactless instrumental configuration for urea detection in aqueous solutions.
• To leverage urea's near-infrared absorption properties for quantitative analysis.

Main Methods:

• Utilized two near-infrared LEDs (1450 nm and 2350 nm) as light sources.
• Employed a hollow glass tubing with a 1 mm optical pathlength to contain aqueous samples.
• Compared photodiode and thermal optical power detector performance with varied signal processing techniques.

Main Results:

• Demonstrated a linear relationship between the ratio of transmitted light intensities at 1450 nm and 2350 nm and urea concentration.
• Achieved sensitive detection of urea in water solutions ranging from 0 to 525 mg/mL.
• Validated the system using commercial diesel exhaust fluid (AdBlue™) samples.

Conclusions:

• The developed near-infrared spectroscopic system provides a viable, cost-effective solution for contactless urea sensing.
• The method is reagent-free and suitable for real-time monitoring in diverse applications.
• The linear response across a wide concentration range ensures reliable urea quantification.