Rapid analysis of six cytokinins in tomato plants using phenylboronic acid and ionic liquid functionalized monolithic...

In this study, 4-vinylphenylboronic acid, ionic liquid, and dipentaerythritolhexakis(3-mercaptopropionate) were used as functional monomers to prepare monolithic column in fused-silica capillaries by thermally induced sulfhydryl-alkenyl click polymerization. Based on the properties of 4-vinylphenylboronic acid and ionic liquid, the monolithic capillary column (VPBA-SH-IL) exhibited excellent permeability and chemical stability with the ability to efficiently enrich trace amounts of cytokinins from complex substrates via B←N coordination, π-π interactions, cation-π interactions, S-π interactions and hydrophobic interactions. Under the optimal adsorption conditions, the adsorption efficiency of VPBA-SH-IL for six cytokinins could reach more than 95 %, and the adsorption capacities ranged from 0.18 to 0.99 mg·m^-1. A reliable and sensitive method for the determination of six cytokinins in organs of tomato (root, stem, leaf and fruit) was established by using the monolithic capillary column as in-tube solid-phase microextraction coupled with UHPLC-MS/MS. The developed method showed a wide linear range (0.010-10.0 μg·L^-1) and low limits of detection (1.6-3.3 ng·L^-1). The recoveries of the six cytokinins in spiked samples ranged from 80.6 % to 108 % with the relative standard deviations of 2.4-8.7 % (n = 5). The VPBA-SH-IL shows good potential for extraction and analysis of trace cytokinins in complex matrices such as plants, which is of great significance in exploring the mechanism of plant growth and development.