Quantitation of indole-3-acetic acid by LC with electrochemical detection in etiolated hypocotyls of Lupinus albus

The objective of this work was to develop a simple procedure to determine the level of the plant hormone indole-3-acetic acid (IAA) in etiolated lupin hypocotyls using liquid chromatography with amperometric detection. A C18 reversed-phased column was used with a potential of +0.85V applied to the carbon electrode. We used two different auxin extraction procedures from lupin hypocotyl and similar quantities of indole-3-acetic were obtained. The method was capable of determining indole-3-acetic acid with a limit of quantification of 2.2 pg. The identity of the indole-3-acetic acid in lupin was confirmed by GC-MS. The content of this hormone in three zones of hypocotyl (apical, central, and basal) was estimated and a concentration gradient: apical > central > basal, was observed with mean values of 657 ng IAA/g FW 261 ng IAA/g FW and 145 ng IAA/g FW respectively.