Liquid chromatographic determination of endogenous phytohormones in vegetable samples based on chemical derivatization with 6-oxy(acetylpiperazine) fluorescein.

In phytohormone analysis, mass spectrometry (MS)-based methods are primary and powerful tools. However, complex sample preparation and high cost are problems for their application. As a complement for MS-based methods, a new fluorescent labeling reagent for carboxylic acids, 6-oxy(acetylpiperazine) fluorescein (APF), has been used for the determination of endogenous phytohormones, including indolebutyric acid, 1-naphthaleneacetic acid and 2,4-dichlorophenoxyacetic acid. The derivatization yield was maximized by optimizing derivatization conditions in detail, and the derivatives of three phytohormones could be separated completely in 15 min on a C18 column with fluorescence detection at lambda(ex)/lambda(em) = 467/512 nm. The derivatization limits could reach 0.1 microM, and the detection limits (signal-to-noise ratio = 3) were 4.43-14.2 nM. The proposed method has been applied to the determination of the exogenous phytohormones in the crude extracts of vegetable samples without extra purification and enrichment with recoveries of 94.2-102.4%.