Preliminary Study Of The Trace Analysis Based On The Application Of Several Modified Materials

As the most commonly used composite materials,silica gel and graphene oxide(GO)have many advantages,such as large surface area,strong adsorption capacity,and so on.Especially,they are used for separation and enrichment in complex matrix or trace components,because possessing convenient,fast,low cost,and so on.In order to improve the adsorption efficiency and selectivity,the surface of these materials is usually modified by physical or chemical methods.This paper is devoted to the synthesis of new modified silica gel and GO,which were used for separation and enrichment of trace amounts of noble metals and heavy metal ions;and gold nanoparticles decorated GOtodetect traceconcentration of nitrite ions.The main contents are as follows:PartⅠ: A solid phase extractant(2-amino-5-mercapto-1,3,4-thiadiazole modified silica gel)was prepared,which was characterized by Fourier Transform Infrared Spectrometer(FTIR Spectrometer).It could be use to separate,enrich and detect trace gold combined with XRF technique.We optimized the experimental conditions,including pH value,elution volume,maximum adsorption capacity and maximum enrichment ratio.The results show that the optimal pH value is 1.0;the content of adsorbent is 50 mg;Different concentrations of Fe(III),Ni(II),Co(II)and other elements almost did not influence the current response of nitrite;2 mL eluent with hydrochloric acid and thiocarbamide solution could be completely eluted;adsorption capacity of this adsorbent is 7 mg/g the factor of enrichment time is 125;the detection limit is 0.017 μg/mL and the relativestandard deviation(RSD)of thesamples is 4.3%.The results are satisfactory.Part II: A solid phase extractant(L-cysteine modified silica gel)was prepared by FTIR spectroscopy and used to separate and enrich trace gold,and then analyzed by XRF.Under the optimal conditions,the results show that the maximum enrichment factor of gold element is 100,the maximum enrichment factor of the gold element is 100 and detection limit is as low as 0.017μg/mL.The method used in gold concentrate in the determination of the recovery rate is more than90%.Part Ⅲ: Firstly,a new solid phase extraction agent,L-cysteine modified graphene oxide(SH-GO),was successfully synthesized.GO was fabricated by a modified Hummers’ method,and then characterized by FTIR spectroscopy,Raman spectra,X-ray diffraction(XRD),XRF.It was used to determine the concentration of trace gold,combined with ICP-AES.Further,the effects ofpH,the type of eluent,the volume of elution,the maximum adsorption capacity,and the amount of eluent were optimized.The results show that the maximum enrichment factor is 50,the detection limit is 0.035 μg/mL,and the maximum adsorption capacity is 44 mg/g.Then this method is used for separation,enrichment and detection of trace gold in the standard samples and water samples,and the results aregood.Part Ⅳ: GO was fabricated by a modified Hummers’ method,After decorated with Fe3O4,the trimethylenetetramine was further modified and characterized by IR,Raman,XRD,XRF,etc.It was used to determine the concentration of lead.Combined with ICP-AES,the parameters such as pH,the type of eluent,the volume of elution,the maximum adsorption capacity,the maximum enrichment,and other factors were optimized.Under the condition of excellent conditions,the maximum enrichment factor of lead element is 50 and the maximum adsorption capacity is 78mg/g.The method is applied to the separation,enrichment and detection of lead in standard sample and water sample,and theapplication effect is fine.Part Ⅴ: Graphene,as a two-dimensional material with superior properties,has been widely used in electrochemical sensing.This chapter synthesizes SH-GO according to the previous part of the method,and then through a mild method to synthesize the gold-decorated SH-GO,which was characterized by UV,Raman,SEM and cyclic voltammetry.Compared with undecorated gold-,Au/SH-GO,decorated modified graphene has a better conductivity and more effectively promotes the electron transfer between the substrate molecules and the probe molecules and the electrodes.Based on its excellent electrocatalytic performance for nitrite ions,we have established a new sensor tousefor detection in theactual sample,and the application effect is Well.