Electromembrane extraction based on carbon nanotubes reinforced hollow fiber for the determination of plant hormones

In this work, an electromembrane extraction (EME) technique based on carbon nanotubes reinforced hollow fiber (CNTs-HF) was developed and applied to determine two plant hormones in tomato samples. The CNTs-HF was prepared by a feasible physical method in which CNTs were dispersed in 1-hexanol and then immobilized into the wall pores of HF supported by capillary forces and sonication. Subsequently, the CNTs-HF was placed in tomato samples to extract plant hormones under electric field drive. In this mode, porous HF held the extractants and provided excellent sample clean-up ability. 1-Hexanol and CNTs held in the wall pores of HF served as a supported liquid membrane (SLM) and a sorbent, respectively, enabling the enrichment and migration of the analytes. The comparison between CNTs-HF-EME and HF-EME showed that CNTs could increase the overall partition coefficient of analyte in the membrane due to their large surface area and high adsorption capacity. In order to achieve the best extraction efficiency, optimal conditions of CNTs-HF-EME were obtained using 1-hexanol as the SLM, 105 V of applied voltage, pH 9 and 13 of the sample solution and the acceptor phase, respectively, an extraction time of 0.5 min and a stirring rate of 1200 +/- 24 rpm. Under these conditions, CNTs-HF-EME was able to provide higher enrichment factors and lower limits of detection and quantification within a shorter extraction time, compared to the HF-EME. This newly developed extraction method has been shown to be a rapid, feasible, and cost-effective sample pretreatment technique for trace analysis in complex matrices.