Abstract
Indole-α-pyrone was used by A. Stoessl and M. A.Venis for the purpose of fluorometric determination of IAA.
In this work, analytical conditions have been studied to improve their method. The following analytical procedure is recommended : An aqueous solution of 1 ml contained 5× 10-51 × 10-7 mol/l of IAA is taken in a test tube and dried in a vacuum desiccator at room temperature. Then 0.5 ml of mixture (1 + 1 by vol.) of caproic anhydride and boron trifluoride (BTF) is added into the tube. After standing for 15 min. at 0°C, 5 ml of KHCO3(5% W/V) solution is added. After shaking, indolo-α-pyrone formed is extracted with 5 ml of n-butanol. The fluorescence is measured at 500 nm by using an excitation at 440 nm. By the proposed method, for intensity of the fluorescence is remarkably enhanced. This reaction depends on the catalytic action of Lewis acid. Interference by diverse indole compounds and inorganic ions was studied in mole ratio range from 10 to 100 times against 1 ml of IAA (5 × 10-7 mol/l). In the determination of IAA, many indole compounds except 5-hydroxy-IAA and indole-3-acrylic acid did not interfere.
