Measurement of indolebutyric Acid in plant tissues by isotope dilution gas chromatography-mass spectrometry analysis

An internal standard, ¹³C]indole-2]-indole-3-butyric acid, was synthesized from indole-2¹³C] and was shown to be effective for the quantitative determination of indole-3-butyric acid from plant tissue. When this standard was used along with ¹³C₆]indole-3-acetic acid, both indolic auxins could be quantified from the same tobacco (Nicotiana tabacam) leaf sample by isotope dilution analysis using selected ion monitoring gas chromatography-mass spectrometry for detection.