Photometric starch-iodine determination in plant materials as influenced by ascorbic acid. Critical remarks

• Main Authors: Bogusław Samotus, Elżbieta Doerre, Adam Świderski, Andrzej Ścigalski
• Format: Article
• Language: English
• Published: Polish Botanical Society 2014-01-01
• Series: Acta Societatis Botanicorum Poloniae
• Subjects: Starch-iodine complex; ascorbic acid; interference
• Online Access: https://pbsociety.org.pl/journals/index.php/asbp/article/view/1082

Following the work of Sharma et al. (1990) on the interference of ascorbic acid (AA) with starch-iodine reaction, the present authors repeated it, giving a proper explanation of the influence of AA in this reaction. AA oxidizes iodine-iodide (I-KI) reagent which makes impossible to form the blue complex with starch. Three measures are suggested to overcome the interference of AA: 1) to titrate starch solution with I-KI reagent and thus work out an I-KI amount for development of blue coloration, 2) to remove from plant material AA (and other reducing soluble substances) by washing the material with cold water or ethanol, and 3) starch solution could be treated with alkali (pH about 9), which destroys AA in 15 minutes. After acidifying the solution and adding I-KI reagent the blue complex can be determined.