| 摘要 |
PROBLEM TO BE SOLVED: To precisely measure the IPA concentration in an aqueous solution containing a very small amount of IPA. SOLUTION: Light of a beam 6a is reflected by a dichroic mirror 10 to introduce only the light of a short wavelength band having a wavelength shorter than 200 nm into the aqueous sample solution in a cell 2. The light in a short wavelength side having a wavelength shorter than 190 nm out of the light is absorbed by water in the sample solution, only the light in a wavelength band of 190-200 nm is reflected by total refrectance mirrors 14a, 14b to be transmitted again through the sample solution in the cell 2, and the light is converged by a lens 16 in a detector 18 to be detected. The light is absorbed therein by the IPA in the sample solution. A reference beam expressing light source intensity not affected substantially by the absorption of the IPA by the light reflected by a reflection mirror 12 of the beam 6b is measured to determine the IPA concentration in the aqueous sample solution based on a difference (differential absorbance) therebetween.
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