Analytical Sciences

Direct Detection of Aqueous CO₂ by Infrared Waveguide Spectroscopy with an Amorphous Fluoropolymer Coating Rod

Hiroki HOTTA,* Yuko MIKI,** Yukiko KAWAGUCHI,** Kin-ichi TSUNODA,** Atsuko NAKAOKA,*** Sho KO,*** and Takashi KIMOTO***

*Department of Chemistry, Nara University of Education, Takabatake, Nara 630-8528, Japan
**Department of Chemistry and Chemical Biology, Gunma University, Tenjin-cho, Kiryu 376-8515, Japan
***Kimoto Electric Company, Ltd., 3-1 Funahashi-cho, Tennoji, Osaka 543-0024, Japan

Infrared waveguide spectroscopy using a sapphire rod coated with an amorphous fluoropolymer (Cytop, Asahi Glass Co., ltd, Japan) has been developed in order to directly observe CO₂ in aqueous solutions. Since the amorphous fluoropolymer has a relatively high gas-permeability and hydrophobic feature, the aqueous CO₂ transmits into the amorphous fluoropolymer coating film, but water cannot penetrate into the film. Good linearity of calibration curves for CO₂ in the gas and the aqueous solution were obtained.

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