Simultaneous determination of cytokinins by high performance liquid chromatography with resonance Rayleigh scattering and mechanism discussion.

A reliable, highly sensitive and highly selective method of high performance liquid chromatography associated with resonance Rayleigh scattering (HPLC-RRS) was developed to detect three cytokinins, namely, 6-benzylaminopurine (BA), kinetin (KT) and zeatin (ZT). In this work, Pd(ii) is added into the system to form ternary ion association complexes for the first time, which results in a lower limit of detection and extends the application of HPLC-RRS. The experimental conditions were optimized. In order to investigate the reaction mechanism, the ternary ion association complexes were characterized by ultraviolet-visible spectrophotometry, dynamic light scattering, scanning electron microscopy and density functional theory calculations. In a HAc-NaAc buffer solution (pH = 4.1), a ternary complex of cytokinin : Pd(ii) : EryB (1 : 1 : 2) was formed. The detection limits (S/N = 3) of BA, KT, and ZT were 0.9, 1.5 and 2.3 ng mL, respectively. In addition, this method was applied for the simultaneous detection of cytokinins in real samples with satisfactory results.