Preparation and measurement of standard organic gases using a diffusion method and a NASICON-based CO₂ sensor combined with a combustion catalyst

The development of new analytical methods for the detection of volatile organic compounds (VOCs) requires the preparation of standard gases at various concentrations. In this study, using a diffusion method where liquid samples were heated and vaporized under a carrier gas flow, we prepared standard organic gases containing acetone or 2,6-diisopropylphenol (propofol), which are breath markers for diabetes and anesthesia depth, respectively. A Pt/Al ₂O₃ combustion catalyst was used in conjunction with a NASICON (Na₃Zr₂Si₂PO₁₂; Na ⁺ conductor)-based CO₂ sensor for the continuous determination of organic concentrations in the sample gas streams; the catalyst allowed for conversion of ppm concentrations of acetone or propofol to CO ₂. The results demonstrate that the present system is feasible for the preparation and concentration determination of standard VOC gases.