Development of Graphene Oxide Functionalized Cotton Fiber Based Solid Phase Extraction Combined with Liquid Chromatography-Fluorescence Detection for Determination of Trace Auxins in Plant Samples

In this work, a convenient and sensitive solid phase extraction (SPE) method was developed based on graphene oxide functionalized cotton fiber (GO-CF), a SPE sorbent followed by liquid chromatography-fluorescence detection (LC-FLD) for determination of trace indole acetic acid, indole propionic acid, indole butyric acid and naphthalene acetic acid. GO-CF was synthesized via covalent bonding method on the surface of cotton fiber, and exhibited higher extraction capacity in comparison with that of cotton fiber. The conditions affecting the extraction efficiency, including sample pH, elution solvent, elution volume, extraction time, and sample volume, were optimized to obtain high extraction recoveries. Under optimal conditions, the calibration curves were linear over the concentration ranging from 2 to 200 ng mL −1 with correlation coefficients between 0.9987 and 0.9998 for all the analytes. The limits of detection were lower than 0.371 ng mL −1 for the four auxins. The intra- and inter-day relative standard deviations (RSDs) were less than 3.5 and 7.1%, respectively. The mean recoveries ranged from 73.5 to 105.4% with RSDs lower than 12.6%. The developed GO-CF–SPE–LC-FLD method has been successfully applied to the analysis of four auxins in real plant samples, including mung bean stalk, mung bean sprout, and tobacco leaf samples. Graphical abstract