Facile preparation of amino-functionalized polyacrylonitrile/graphene oxide electrospun nanofibers for extraction of plant growth regulators in tomato.

In this study, amino-functionalized polyacrylonitrile/graphene oxide nanofibers (NH2-PAN@GO NFs) was prepared and applied as adsorbents for the extraction of plant growth regulators (PGRs) in tomato. A miniaturized and efficient sample pretreatment method, syringe filter-based solid-phase microextraction (SF-SMPE), was developed by packing the prepared NH₂-PAN@GO NFs into a syringe filter. PAN@GO NFs was firstly fabricated via co-electrospinning, followed by amination with hydrazine hydrate to obtain NH2-PAN@GO NFs. The prepared NH2-PAN@GO NFs showed superior adsorption performance for PGRs, which was attributed to the GO incorporation and amino-functionalization. Isothermal adsorption and adsorption kinetic experiments revealed that the adsorption of PGRs by NH₂-PAN@GO NFs conformed to the Freundlich thermodynamic model and the pseudo-second-order kinetic model, respectively. The Box-Behnken experimental design was employed to optimize the operating conditions of SF-SMPE. The optimal conditions were determined to be a solution pH of 7, an adsorbent mass of 7 mg and 1 mL of 15% formic acid-methanol (v/v) as the eluent. The developed SF-SMPE coupled with high performance liquid chromatography equipped with a fluorescence detector (HPLC-FLD), achieved limits of detection and quantification ranging from 0.033 to 0.125 ng mL⁻¹ and 0.109 to 0.415 ng mL⁻¹ for four PGRs, respectively. The developed method was successfully applied to detect PGRs in tomato, 3-indoleacetic acid was identified in original samples. The recoveries of spiked samples ranged from 87.38% to 100.51%, with relative standard deviations of 0.71%-2.62%.