Partial isotope fractionation during high-performance liquid chromatography of deuterium-labelled internal standards in plant hormone analysis: A cautionary note.

Deuterium-labelled indole-3-acetic acid, abscisic acid and phthalimido-1-aminocyclopropane-1-carboxylic acid were found to separate from the unlabelled compounds on reverse-phase high-performance liquid chromatography (HPLC). A similar separation was found for the methyl esters of these compounds on normal-phase HPLC. Such separations may lead to substantial errors when these compounds are used as internal standards for quantitation by gas chromatography-mass spectrometry/selective ion detection, unless the complete chromatographic peaks are collected.