Application Of Magnetic Nitrigen-doped Graphene In Environmental Water Samples Analysis

Firstly,Fe₃O₄-grafted nitrogen-doped graphene nanomaterials were synthesized by chemical co-precipitation method,which was characterized by XRS,SEM and VSM.The adsorption performance of Fe₃O₄/N-G to ten organic pollutions including chlorobenzenes,polychlorinated biphenyls,phenols and anilines was evaluated.The results demonstrated that Fe₃O₄/N-G displayed high adsorption efficiency for TCS,HCB and PCB-153.In order to further explore the adsorption mechanism of Fe₃O₄/N-G as adsorbent,the isotherms and kinetics parameters of the other seven compounds on adsorbents were evaluated.The results showed that the adsorption of PCMX,2-TBP,2,4-DTBP and aniline on Fe₃O₄/N-G is not limited to uniform monolayer adsorption,which may exist in the nonuniform multi molecular adsorption,while 2-MA,3-CA and N,N-DMA were uniform monolayer adsorption.The adsorption kinetics of seven compounds followed the pseudo-second-order kinetic mode.Secondly,an ultrasound-assisted magnetic solid-phase extraction with Fe₃O₄/N-G as the magnetic adsorbent has been developed for the determination of four compounds including TCS,PCMX,HCB and PCB-153 in environmental water samples,in combination with gas chromatography coupled to tandem mass spectrometry.Several factors related to extraction efficiencies,such as the amount of adsorbent,extraction time,sample pH and desorption conditions were investigated.Under the optimized conditions including 6.0 mg of magnetic adsorbent,15 s of extraction time,5 mL of elution solvent and 15 s magnetic separation,an excellent linearity was observed in the range of 0.1¹0 ng/L for the four compounds,with the correlation coefficients ranging from 0.9983 to 0.9999.The limits of detections（S/N=3）ranged from 0.05 to 0.6 ng/L and the limits of quantity（S/N=10）ranged from 0.2 to 2.4 ng/L.The mean recoveries at three spiked levels ranged from 68.2⁹9.6%.The relative standard deviations（RSDs）of intraday and interday varied from 3.3% to 6.9% and from 3.4% to 9.4%（n=6）,respectively.The proposed method was demonstrated to be simple and feasible for the trace analysis of antimicrobial agents and organochlorine contaminants in environmental water samples.In addition,through the analysis of response surface methodology,we can obtain the conclusion that the interaction between amount of absorbent and ultrasonic extraction time is obvious,while the interaction is not obvious between amount of absorbent and water sample pH,and ultrasonic extraction time and water sample pH.Finally,an ultrasound-assisted magnetic solid-phase extraction with Fe₃O₄/N-G as the magnetic adsorbent has been developed for the determination of four compounds including aniline,2-MA,3-CA and N,N-DMA in environmental water samples,in combination with gas chromatography coupled to tandem mass spectrometry.Several factors related to extraction efficiencies,such as the amount of adsorbent,extraction time,sample pH and desorption conditions were investigated.Under the optimized conditions including 10.0 mg of magnetic adsorbent,15 s of extraction time,6 mL of elution solvent and 15 s magnetic separation,an excellent linearity was observed in the range of 0.5¹0 ng/L for the four compounds,with the correlation coefficients ranging from 0.9983 to 0.9999.The limits of detections（S/N=3）ranged from 1.58 to 21.8 ng/L and the limits of quantity（S/N=10）ranged from 4.74 to 65.4 ng/L.The mean recoveries at three spiked levels ranged from 54.8 to 84.9%.The relative standard deviations（RSDs）of intraday and interday varied from 4.9% to 6.4% and from 6.7% to 65.4%（n=6）,respectively.In addition,through the analysis of response surface methodology,we can obtain the conclusion that the interaction between amount of absorbent and ultrasonic extraction time is obvious.