| Polycyclic aromatic hydrocarbons(PAHs)are one of the most widely distributed and the most hazardous persistent organic pollutants(POPs)in the environment.Since PAHs pollutants in environmental samples are generally present in low concentration,the preconcentration of the target analyte and reduction or elimination of the interferences originally present in the samples become one of the most critical steps in the entire analytical process.Solid phase extraction(SPE)has been widely used in extraction and preconcentration of many trace organic compounds due to its advantages of convenient operation,high extraction efficiency and low consumption of organic solvents.Whether the choice of adsorbent is suitable decided the recovery rate and enrichment factor.This dissertation aims at synthesizing and screening adsorbents for the enrichment and determination of trace PAHs in water,optimizing the influencing factors of enrichment efficiency,and establishing an analytical method for the SPE-HPLC-UV of low detection limit,high precision and high accuracy of PAHs pollutants in environmental water samples.The contents of the study are as follows:Graphene/sepiolite(G/Sep)nanocomposites were prepared and characterized by electron microscope.The SPE-HPLC-UV analysis method was established for the detection of polycyclic aromatic hydrocarbons(PAHs)using graphene/sepiolite(G/Sep)as solid phase extraction adsorbent,and achieved high accuracy and sensitivity determination of polycyclic aromatic hydrocarbons(PAHs).Firstly,the instrument conditions of liquid chromatography were optimized,and the mobile phase,gradient elution conditions and detection wavelength of UV detector were determined.Based on this,the influence of the conditions during solid phase extraction(SPE)was studied which are solvent type,elution volume and sample volume.Under the optimal conditions,the target analyte showed a good linear relationship,with the correlation coefficient ranging from 0.999 to 1.000,the LODs were between 0.0005 and 0.0015?g/L,and the relative standard deviations were less than 1.16%.The method was applied to the analysis samples with 76.7%?102.2%recoveries.The method has been successsful applied to the analysis of PAHs in real water samples.Magnetic graphene oxide nanocomposites were prepared by chemical precipitation and investigated their potential as adsorbents in solid phase extraction.The structure of magnetic graphene oxide was characterized by electron microscope.Magnetic graphene oxide was used as adsorbent to enrich and extract PAHs in water samples,and combined with HPLC to detect and analyze them.Under optimized chromatographic experimental conditions,the influence of the conditions in solid phase extraction(SPE)was investigated which are desorption solvent,p H value and ionic strength,and adsorbent dosage.Under the optimal conditions,the linear correlation coefficient was between 0.999 and 1.000,the detection limit was between0.0004 and 0.0013 ?g/L,and the relative standard deviation was less than 2.52%.For the actual water sample detection,the standard recovery rate was 76.3%?94.6%.The results indicated that as a SPE adsorbent,magnetic graphene oxide has a great potential for the preconcentration of PAHs in water samples.Two novel nanocomposites prepared in this paper were compared.Firstly,the adsorption properties of PAHs were compared between graphene/sepiolite and magnetic graphene oxide.According to the recovery data of the actual water sample,the adsorption effect of graphene/sepiolite was better than that of magnetic graphene oxide.In addition,the preparation of graphene/sepiolite composites is simpler,cheaper,faster and can be done directly in the laboratory.More importantly,the desorption step using graphene/sepiolite composites can be carried out with an aqueous solution of a non-ionic surfactant,making the SPE process green and environmentally friendly.Therefore,the method based on graphene/sepiolite composites is more suitable for the analysis of PAHs in environmental waters samples. |
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