RESUMO
A simple and rapid method was developed for the determination of three free cytokinins, namely, N(6)-(Δ(2)-isopentenyl)adenine, zeatin, and dihydrozeatin, in plants using TurboFlow on-line cleanup liquid chromatography combined with hybrid quadrupole-Orbitrap high-resolution mass spectrometry. The samples were extracted using acetonitrile, and then the extract was purified on a C18-p column, in which the sample matrix was removed and the analytes were retained. Subsequently, the analytes were eluted from the extraction column onto the analytical column (Hypersil Gold C18 column) prior to chromatographic separation and hybrid Q-Orbitrap detection using the targeted-MS(2) scan mode. The linearity was satisfactory with a correlation coefficient of >0.999 at concentrations ranging from 5-5000 pg/mL. The limits of quantification for the analytes ranged from 4.2-5.2 pg/mL. The intra- and inter-day average recoveries of analytes fortified at three levels ranged from 85.4-108.2%, and the intra- and inter-day relative standard deviations ranged from 4.04-8.57%. The method was successfully applied for the determination of free cytokinins in different tissue samples of Oryza sativa and Arabidopsis thaliana.