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Quantitative Determination of Indole‐3‐Acetaldehyde. II.
Author(s) -
Lahsen Poul
Publication year - 1966
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1966.tb07063.x
Subject(s) - chemistry , acetaldehyde , reagent , indole test , chromatography , indole 3 acetic acid , ether , aldehyde , acetonitrile , nuclear chemistry , organic chemistry , biochemistry , ethanol , auxin , gene , catalysis
The method by Larsen and Klungsöyr (1964) for the quantitative determination of indole‐3‐acetaldehyde (IAAld) was modified for the purpose of eliminating the need for filtration after oxidation of the IAAld to indole‐3‐acetic acid (IAA). The essentials of the modified method are as follows: Samples of IAAld or IAA containing 0.015 to 0.15 μmol (ca. 2.5 to 25 μg) dissolved in peroxide‐free ether are evaporated to dryness and redissolved in 1.5 ml 0.02 M Ag2SO4. The oxidation is carried out in dim light by adding 0.5 ml 0.12 N NaOH. After 1.5 min, 2 ml of a modified Salkowski reagent are added. The optical density at 525 nm is read on a spectrophotometer after 75 min. The modified Salkowski reagent consists of 100 ml 0.05 M Fe2(SO4)3 in 1.5 N H2SO4; 240 ml H2O; and 160 ml cone. H2SO4 (sp. gr. 1.84). O.D. readings are identical for equal samples of IAAld and IAA (the latter used as a standard) up to 0.08 μmol (O.D. = 0.32). Larger quantities of IAAld may be determined when using pure IAAld as a standard, but at 0.20 μmol the O.D. for IAAld is lower than for IAA (0.69 as against 0.72). Indole‐3‐acetonitrile, tryptophol, indole‐3‐carboxylic acid, and indole‐3‐aldehyde all give O.D. values lower than 0.1 when tested at 0.20 μmol under the same conditions as described for IAAld and IAA.