13C6-[benzene ringj-indole-3-acetic acid: A new internal standard for quantitative mass spectral analysis of indole-3-acetic acid in plants

Abstract

Indole-3-acetic acid (IAA) labeled with 13C in the six carbons of the benzene ring is described for use as an internal standard for quantitative mass spectral analysis of IAA by gas chromatography/selected ion monitoring. ['3C6jIAA was compared to the available deuterium labeled compounds and shown to offer the advantages of nonexchangeability of the isotope label, high isotopic enrichment, and chromatographic properties identical to that of the unlabeled compound. The utility of I'3C46IAA for measurement of endogenous IAA levels was demonstrated by analysis of IAA in Lemna gibba G-3.