2020 Volume 69 Issue 12 Pages 693-706
The RGB-based reproducing method for absorption spectra was applied to colorimetric analysis with smartphone-captured digital color images. The present study demonstrates the reproduction of the spectra of aqueous potassium permanganate coexisting with glucose under a basic condition, phenol red solutions under various pH conditions, and aluminum-eriochrome cyanine R complexes coexisting with cationic surfactants. The reproduced absorption spectra were coincided with the spectra obtained by conventional spectrophotometry with high accuracy. We also applied the present method to water quality tests of environmental water samples, which determined chemical oxygen demand values, pH values and the cationic surfactant concentration. We have confirmed that absorptions spectra were also reproduced even with the environmental water samples. Moreover, the results obtained from the reproduced spectra were almost identical to those obtained from the spectrophotometric spectra, showing the potential of the present method for on-site ratiometric analysis with smartphones. The present method would enable the smartphone-based ratiometric analysis without any monochromatizing equipment such as gratings and imaging spectrometers.
