Reagent-free mid-ir optical sensor for chloramine detection in water

Overview

This solution offers a reagent-free optical detection method for chloramine in water using mid-infrared (IR) absorption spectroscopy. Conventional chloramine detection relies on wet-chemical reagents and bulky instruments such as FTIR spectrometers, which limits their use to laboratory settings. By selecting specific mid-IR wavelengths where chloramine exhibits strong absorption (over 95%) while water absorbs very little (under 5%), the approach delivers highly selective and sensitive detection in a compact, low-cost footprint. The sensor is designed for seamless integration with existing water filtration and treatment infrastructure, enabling continuous, real-time monitoring without consumable reagents.

Technical specifications

Key features:

• Reagent-free operation — eliminates the need for chemical reagents, reducing cost, waste, and maintenance
• Mid-IR absorption principle — leverages the unique infrared absorption signature of chloramine molecules for selective identification
• Targeted wavelength selection — uses specific laser or LED emission wavelengths matched to chloramine's absorption band, minimizing interference from water
• Photodetector-based readout — measures transmitted IR light intensity through a water-carrying tube to quantify chloramine concentration
• Small form factor — designed for compact, in-line deployment rather than benchtop laboratory use
• Filtration system integration — can be embedded directly into water treatment and distribution pipelines

Technology readiness level

The concept is grounded in well-established IR absorption spectroscopy principles and validated by extensive prior use of FTIR for analyte identification in liquid samples via ATR techniques. The current stage focuses on adapting this proven detection chemistry into a miniaturized, field-deployable configuration. Next steps include building and testing a prototype with the identified mid-IR wavelengths, demonstrating detection sensitivity and selectivity against water background, and validating integration with representative water filtration systems.