Investigations On The Solid Phase Micro-extraction And Sensing Of Bisphenol A With Graphene Oxide-based Composites

As a two-dimensional carbon material,graphene has excellent mechanical,electrical,optical,thermodynamic and chemical properties.Meanwhile,it can be combined with other materials through surface modification to obtain functional composites.Therefore,graphene has been widely used in the fields of materials,electronics,sample pretreatment and sensing.In present study,two different graphene-based composites have been prepared and applied to bisphenol A(BPA)extraction/separation and sensing.By virtue of the large surface area of graphene oxide(GO),TpBD-GO composite is obtained by monomer-mediated modification of covalent organic skeleton material TpBD on the surface of GO,and the obtained TpBD-GO composite is characterized by scanning electron microscopy,Raman spectroscopy,infrared spectroscopy,X-ray diffraction,thermogravimetry,and N2 adsorption-desorption techniques.The results indicated that TpBD grows uniformly vertically on the surface of GO,and the TpBD-GO composite has the structural characteristics of GO and TpBD,and exhibits good thermal stability and micropore structure.The composite is coated on the surface of quartz fiber and used for the adsorption,separation and enrichment of BPA in the water phase,Subsequently in situ mass spectrometry analysis and detection are performed.With an adsorption time of 5min,the established solid phase microextraction process offers enrichment factor of 184 for BPA.Methanol solution containing 0.1%ammonia as desorption agent and an flow rate of 10 ?L/min,BPA in the range of 0.1-10 ?g/L is accurately detected,and the detection limit is 17 ng/L.The RSD of inter and intra extraction fiber are 4.9%and 6.4%,respectively.The established separation-enrichment-in-situ mass spectrometry detection process is applied to the detection of BPA in water samples,giving the recoveries between 91.6-115.6%.Thereafter,Rh2O3 nanoparticles are prepared by hydrothermal method,and Rh2O3-GO composite is then prepared by ultrasonic mixing method.The obtained materials are characterized by scanning electron microscopy and X-ray diffraction.The results show that Rh2O3 are uniform nanoparticles,and wrapped by GO after being combined with GO.A novel electrochemical sensor is thus developed by coating the Rh2O3-GO composite onto the surface of glassy carbon electrode for the cyclic voltammetry analysis of BPA.Under the optimal detection conditions(reduction potential of-1.2V,reduction time of 120s,scanning rate of 0.1v/s),the linear range for BPA detection is 0.6-40 ?mol/L,and the detection limit is 0.12?mol/L.This sensor is applied to the analysis of BPA contents in beverage samples,giving satisfactory recoveries of 93.0%-99.0%.