Graphene oxide composites for magnetic solid-phase extraction of trace cytokinins in plant samples followed by liquid chromatography-tandem mass spectrometry

In this work, an easy, effective, and sensitive method based on graphene oxide@silica@magnetite composites as adsorbent of magnetic solid-phase extraction combined with liquid chromatography and tandem mass spectrometry, was established and validated for the trace analysis of cytokinins in different plants. The prepared magnetic composite was characterized by infrared spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, and magnetic hysteresis. Under the optimized conditions, good linearities in the range of 0.5-100 ng/mL were obtained with the corresponding linear correlation coefficient >0.9989 for the investigated four cytokinins, and good sensitivity levels were achieved with low detection limits ranging from 93 to 120 pg/mL. The established magnetic solid-phase extraction with liquid chromatography and tandem mass spectrometry method has been validated in the separation and analysis of four cytokinins in plant samples with good recoveries between 78.9 and 97.3% for four cytokinins with the relative standard deviations lower than 13.5%.