Solid Phase Extraction And Microextraction Based On Graphene Oxide And Its Application

Sample pretreatment is one of the most important steps in the analysis of complicated samples. Developing high efficient and selective pretreatment technology has been gained increasing attention. Graphene (G) has been widely used as sorbent in solid phase extraction (SPE) and soild phase microextraction (SPME) because of its huge surface area, good thermal and chemical stability. In this paper, a novel in-tube SPME based on graphene oxide (GO) was developed for selective extraction of triazine herbicides. Also GO coated SiO2nanoparticals (GO@SiO2) were prepared by chemical bonding method and used for efficient removal of antibiotics in water.A novel in-tube SPME based on GO was developed. Monolayer GO sheets were covalently bonded onto the inner wall of a fused-silica capillary using3-aminopropyltriethoxysilane (APTES) as a cross-linking agent. The GO coating was characterized by Raman spectra and scanning electron microscope (SEM). Results showed that the GO coating was-30nm in thickness, and possessed a homogeneous, porous, and wrinkled structure, two characteristic Raman peaks. Its performance was evaluated by the extraction of triazines aqueous solutions. Flow rate of the sample, sample volume, pH value, and ion strength were studied. The best results could be obtained with0.2mL/min of flow rate,15mL of sample volume, pH5-7, and1.0mol.L-1of ion strength. The high extraction efficiency mainly attributed to π-π stacking and hydrogen bonding interactions. It was stable for at least100replicate extractions. The in-tube SPME was used for the determination of triazines by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The achieved detection limits were0.5-5.0ng/L. The reproducibilities of single column and column-to-column were3.4-5.1%and5.5～9.5%for replicate extractions, respectively. The method was applied for the analysis of triazine herbicides in tap water, seawater, and river water, and the recoveries were82.8-96.8%,86.2-97.8%, and81.6-97.6%, respectively.Graphene oxide was successfully modified onto the surface of SiO2nanoparticles by using APTES as a cross-linking agent. The prepared GO@SiO2nanoparticles were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), elemental analyzer, and thermogravimetric analysis (TGA). Absorption experiments were carried out using five antibiotics, including tetracycline hydrochloride (TCH), ofloxacin (OFL), rifampicin (RFP), sulfamethoxazole (SFT), and chloramphenicol (CAM). The adsorption behavior of GO@SiO2nanoparticles to the antibiotics fitted Langmuir adsorption isotherm (R2>0.9960) and pseudo-second-order kinetics model. The absorption capacity of the GO@SiO2nanoparticles to TCH, OFL, RFP, SFT, and CAM were0.316mg/g,0.291mg/g,0.265mg/g,0.251mg/g, and0.209mg/g, respectively. Finally, the GO@SiC>2was used to absorb the five antibiotics in tap water, and the removing efficiencies were68.85%,60.76%,58.34%,51.72%, and47.58%, respectively.