Development of a Strong Cation Exchange Method for Purification and HPLC Assay of Gibberellin-Sterol Inhibitors in Plant Tissue

An enhanced purification method is developed for the gibberellin-sterol inhibitor, paclobutrazol (PP333; [(2RS,3RS)- 1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4 triazol-1-yl) pentan-3-ol]), utilizing solid-phase, strong cation exchange (SCX) chromatography. Exogenous paclobutrazol is derived from treated apple foliage (Malus domestica Borkh.) and quantitated by C18 reverse-phase high-performance liquid chromatography (HPLC) following sample purification on C18 and SCX sorbents. Several methods are evaluated for the elution of paclobutrazol from an SCX column including counter ions (Ba, Ca, Na) with and without acetonitrile. The optimum elution system is ammoniacal—methanol at 60:40 (v/v). Addition of the SCX sorbent purification step in paclobutrazol analysis results in a high recovery rate and substantial degree of purity which easily facilitates separation and quantitation by HPLC.