Magnetic reduced graphene oxide functionalized with β-cyclodextrin as magnetic solid-phase extraction adsorbents for the determination of phytohormones in tomatoes coupled with high performance liquid chromatography.

A β-cyclodextrin (β-CD) functionalized magnetic reduced graphene oxide composite (Fe3O4/RGO@β-CD) has been prepared and its application as a selective adsorbent for the determination of the two naphthalene-derived phytohormones (1-naphthalene acetic acid (NAA) and 2-naphthoxyacetic acid (2-NOA)) has been investigated. Magnetic reduced graphene oxide composite (Fe3O4/RGO) was first synthesized via in situ chemical precipitation method and then β-CD was applied to further functionalize the resultant Fe3O4/RGO composite. The as-prepared Fe3O4/RGO@β-CD was characterized by Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Compared with Fe3O4/RGO, the as-prepared Fe3O4/RGO@β-CD showed better molecular selectivity and higher extraction efficiency for NAA and 2-NOA by dint of the size complementarity brought by the introduction of β-CD. Response surface methodology (RSM), a multivariate experimental design technique, was used to optimize experimental parameters affecting the extraction efficiency in detail. Under the optimal conditions, good performance data was obtained. The calibration curves were linear over the concentration ranging from 2 to 600 ngg(-1) with correlation coefficients (R(2)) between 0.9995 and 0.9997 for all the analytes. The limits of detection (LODs) were 0.67 ngg(-1) for both NAA and 2-NOA. The intra- and inter-day relative standard deviations (RSDs) were less than 6.02% and 7.34%, respectively. The recoveries ranged from 91.45% to 95.89%. Taken together, the proposed method was an efficient pretreatment and enrichment procedure and could be successfully applied for selective extraction and determination of naphthalene-derived phytormones in complex matrices.