Analytical Sciences

Tristimulus Colorimetry Using a Digital Still Camera and Its Application to Determination of Iron and Residual Chlorine in Water Samples

Yasutada SUZUKI,* Masatoshi ENDO,** Jiye JIN,*** Kenji IWASE,* and Masaaki IWATSUKI*

*Department of Applied Chemistry, Interdisciplinary School of Medicine and Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
**Department of Chemistry and Chemical Engineering, Faculty of Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, Yamagata 992-8510, Japan
***Department of Chemistry, Faculty of Science, Shinshu University, 3-1-1, Asahi, Matsumoto, Nagano 390-8621, Japan

Tristimulus colorimetry using a digital still camera (DSC) as a colorimeter has been developed. A photograph of a sample and standard solutions was taken simultaneously with the DSC, and it was transferred to a PC. On the PC, the colors of the sample and of the standard solutions were analyzed and L^* (brightness), a^* (red-green component), and b^* (yellow-blue component) values were determined with laboratory-made software. A dedicated light-box containing white-color LEDs as light source was made of white acrylic to make constant exposure at each photograph. Various settings of the DSC, such as exposure mode, white balance, and so on, that affect analytical figures, were studied with determination of iron with 1,10-phenanthroline. This method was successfully applied to the determinations of iron in a river water sample and of residual chlorine in tap water samples with N,N-diethylphenylenediamine (DPD).

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