Advanced Mid-Infrared Sensor for the In Situ Detection of Disinfection Byproducts in Water

The disinfection of drinking water lowers pathogenic infection risks, but it may introduce chemical hazards from the formation of disinfection byproducts (DBPs), particularly via the reaction of the disinfectant with natural organic matter in the aqueous phase. Increased exposure to DBPs poses significant risks to human health, owing to their pronounced cytotoxic, mutagenic, and carcinogenic properties. Therefore, efficient real-time detection of these micropollutants remains a challenge. In this study, a portable sensing system for the simultaneous detection of multiple environmentally relevant DBPs in water was developed. Advanced mid-infrared fiber optic evanescent wave spectroscopy (MIR-FEWS) system facilitates the in situ simultaneous detection and quantification of multiple DBPs, including trihalomethanes, haloacetic acids, haloacetonitriles, oxyhalide compounds, and haloketones. The active optical transducer (an MIR-transparent silver halide fiber sensing element) was coated with a polymeric molecular recognition membrane (namely poly(styrene-co-butadiene)) mounted inside a micro-flow cell and coupled to a compact broadband Fourier transform infrared spectrometer. The hydrophobic polymer coating enriches non-polar DBPs within the penetration depth of the evanescent wave and improves the limit of detection of the fifteen tested DBPs. Linear calibration functions of simultaneously detected DBPs revealed limits of detection at low ppb concentration levels close to the EU regulatory limits of drinking water. Such an innovative label-free analytical platform with improved detection sensitivity is an essential tool for the safety of water sources. The developed MIR-FEWS sensing prototype was successfully tested in the first-field deployment study, demonstrating strong potential for long-term, real-time, low-ppb in situ detection of multicomponent DBPs.