Intrinsic UV absorption spectrometry observed with a liquid core waveguide as a sensor technique for monitoring ozone in water

Abstract

The industrial use of ozone as a sanitizing agent in water treatment and food processing in recent years calls for sensor technologies for monitoring ozone in water for process control. Ozone molecules absorb UV light with a peak absorption wavelength at 254 nm. This property has been used in this work to develop a simple sensor technology for online, real-time continuous monitoring of trace ozone in water. A Teflon AF2400 tube filled with pure water forms a liquid core waveguide (LCW), which is used as a long-path-length optical absorption cell. This pure water filled tube was deployed into a water sample. Ozone molecules dissolved in the water sample permeate through the Teflon AF2400 tube wall and dissolve in water filled in the tube. This prevents interference species from entering the LCW, and eliminates interferences. The optical absorption signal of the long-path-length cell at 254 nm measured by guiding light through the LCW is used as a sensing signal. This simple structured sensor does not involve any chemical reagent, is reversible, and has a response time <4.5 minutes. It can be used to detect ozone in water samples down to 3.6 × 10⁻⁹ mol L⁻¹.