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-2[¹³C] 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.