Determination of Acidity Constants of p-Rosolic Acid and Bromoxylenol Blue by Solution Scanometric Method

Recently, solution scanometry, as a new, simple, fast, portable, and economic method has been introduced for determination of acidity constants of indicators and dyes. In this study, a method was applied for the determination of the acidity constant of p-Rosolic acid (RA) and Bromoxylenol blue (BXB) indicators. The method is based on scanning of Plexiglas® sheet containing colored solutions with a flatbed scanner. The obtained images were analyzed to red, green, and blue (RGB) values using software written in visual basic 6. For comparison, the acidity constants of the indicators were determined by spectrophotometric method using the Hypspec program. The corresponding distribution diagrams were also drawn through the Hyss2009 program. The comparison between the presented and traditional UV-Vis spectrophotometric method was performed, and similar trends were observed in the results of both methods. The obtained values of pKa by solution scanometric and spectrophotometric methods showed a good agreement with the corresponding values reported in the literature.