One-Step in Situ Preparation of Fe3O4/Carboxylated Multi-Walled Carbon Nanotube Hybrid for the Determination of Caffeine in Carbonated Beverages

Abstract

Abstract Magnetic carboxylated multi-walled carbon nanotubes (Fe3O4-MWCNTs-COOH) have been prepared via in situ preparation. The Fe3O4-MWCNTs-COOH composite was characterized by transmission electron microscopy, X-ray diffraction and vibrating sample magnetometer, and then was successfully applied for the determination of caffeine in carbonated beverages coupled with high performance liquid chromatography. Compared with cetyltrimethylammonium bromide modified magnetic nanoparticles (Fe3O4/CTAB), chitosan modified magnetic carboxylated multi-walled carbon nanotubes (Fe3O4-MWCNTs-COOH/Chitosan), magnetic hydroxylated multi-walled carbon nanotubes (Fe3O4 enclosure MWCNTs-OH) and a hybrid which was composed of magnetic carboxylated multi-walled carbon nanotubes and magnetic hydroxylated multi-walled carbon nanotubes (Fe3O4 enclosure MWCNTs-OH-MWCNTs-COOH), the Fe3O4-MWCNTs-COOH composite exhibited better extraction efficiency for caffeine. The main parameters affecting the extraction efficiency were optimized in detail. Under the optimal conditions, satisfactory performance was obtained. The calibration curve was linear over the concentration range of 7.0 to 600.0 ng mL−1 with correlation coefficients (r) between 0.9993 and 0.9995. The limit of detection was 2.0 ng mL−1. The recoveries were between 97.5% and 101.2% with relative standard deviations ranging from 1.8% to 3.7%. Overall, the proposed method was an effectual pretreatment and enrichment procedure and could be utilized for the analysis of caffeine in complex matrices.