The feasibility study on the colorimetric measurement of pH under acidic conditions using pH indicator papers and image analysis

Abstract

ABSTRACT This study investigates the colorimetric measurement of pH 1–3 using both RGB (red, green, and blue) and CMY (cyan, magenta, and yellow) color systems to address reliable pH measurement methods in aqueous solutions. The experiment utilized pH indicator papers to measure solutions with pH values ranging from 1 to 3. Six hundred measurements were taken for each pH level, and the resulting color changes were analyzed using a free image analysis software provided by the Korean Agency for Technology and Standards. Key findings from the RGB analysis show that for pH 1, R values predominantly fell between 172 and 227, while at pH 3, R values significantly decreased to a range of 71 to 144. In the CMY analysis, cyan values were consistently zero across all pH levels, while magenta and yellow values exhibited varying distributions depending on the pH. The study revealed that the R value in the RGB system is particularly useful for distinguishing between pH 2 and 3, while the M value in the CMY system proved effective in differentiating between pH 1 and 2. These results demonstrate the potential of colorimetric analysis using both RGB and CMY systems as a simple, cost-effective, and reliable method for pH measurement.