Detection of Organic Molecules Dissolved in Water Using a γ-Al₂O₃ Chemiluminescence-Based Sensor

Abstract

A new method is proposed for recognizing organic molecules dissolved in water using a chemiluminescence-based sensor made with a γ-Al₂O₃ catalyst. When a mixture of air and organic molecules, e.g. ethanol and acetone vaporized from a solution, flows around the sensor, chemiluminescence (CL) is emitted during its catalytic oxidation. The CL spectra consist of subbands peaking at the same wavelengths independent of the type of vapors. The peak wavelengths of these subbands are the same as those for CL with a CaCO₃ catalyst. The relative CL intensity of each band, however, depends on the type of the vapor and the temperature of the sensor. This implies that CL originates in the same kinds of luminous species produced during the course of catalytic oxidation. By keeping a sample gas around the sensor in a state of laminar flow and by keeping the catalytic oxidation on the sensor under the diffusion-controlled condition, the CL intensity becomes stable and reproducible. The CL intensity is proportional to the concentration of these organic vapors in the gas phase within the concentration range of from 1 - 500 ppm.