白色発光ダイオードとRGBカラーセンサーを用いる簡易な光度滴定用検出器の開発と鉄鋼試料中クロム分析への応用

抄録

A simple photometric detector for titration was developed using a white LED and an RGB color sensor as the light source and detector, respectively. This detector could record the color change of the sample solution during titration. The color sensor has 12-bit resolution for each red, green, and blue channel. The detector included a magnetic stirrer, and the controller controlled the mixing of a sample solution. The RGB values were transferred to a PC via a USB port. They were automatically converted to absorbance and L*a*b* data, and the results were displayed as titration curves. However, the volume of titrant added to the sample must be manually entered into the PC. The detector is as compact as 125 mm × 90 mm × 90 mm. First, the analytical performance of the titrator was evaluated by standardizing the EDTA solution with calcium carbonate. Then it was applied to the determination of chromium ions in synthesized steel samples according to the method indicated in JIS G 1217:2017, Annex 1 (normative). This method uses ammonium peroxodisulfate oxidation followed by potassium permanganate titration. This detector's function is not only helpful for objectively identifying the endpoint of a titration but also valuable for transferring the veteran's skill in endpoint determination to a novice technician, since subtle color changes can be recorded as numerical data.