Feasibility Study of Purple Sweet Potato (Ipomea batatas L.) Beet Extract as An Acid Base Titration Indicator Sura Menda Ginting (a), Ezra Winnerita Malau (a)
(a) Chemistry Education, University of Bengkulu
Abstract
Acid Base titration is an analytical method for acid or base concentration determination. Acid-base indicators is often used to determine the endpoint of the titration where it shows a contrast colour change. For acid-base titrations, these changes should be near or at the pH range of equivalent point of the titrant and the analyte. Plant extract contains anthocyanin can be used as acid-base indicators as anthocyanin can form flavylium (AH+) which has red color in acid condition and deprotonated into carbinol followed by quinoidal base in base condition, which has pale color and bluish purple respectively. Purple sweet potato beet extract can be used as an alternative of acid-base indicators as it contains anthocyanin. However, to use it as acid-base titration, the color change must be at the pH range of the equivalent point. The extract shows the color change from pink/purple in acid condition, to colorless and then to green followed by yellow when tested with solution from pH 1-14. Further investigations by spectrophotometer UV-Visible shows changes in λ-max from 518-558 nm (purple/pink) at pH range from 1-9 to 600-616 nm (green/blue) at pH range of 10-11. Application of this indicator to the titration process shows that the concentration difference between calculation and the actual concentration is between 0,1-0,9 % where it is concluded that the performance of the indicator is effective for titration process
