| Metal speciation analysis is a valuable tool for human health risk assessment,environmental monitoring and food quality control.Arsenic,mercury and lead are all toxic metals to human body,and their toxic properties are highly dependent upon the chemical forms of the three metals.Therefore,it is necessary to determine the speciation information of arsenic,mercury and lead.Developing reliable multi-elemental speciation analysis methods can save analytical time,reduce the analytical cost,and decrease solvent waste.High performance liquid chromatography coupled with inductively coupled plasma mass spectrometry（HPLC-ICP-MS）combines high separation selectivity of HPLC,and high sensitivity,wide linear range（7 to 9orders of magnitude）and low background of ICP-MS,drawing extensive interest from analytical community in multi-elemental speciation analysis.In the first chapter,the significance of speciation analysis is stated initially.The speciation of arsenic,mercury and lead and the single-elemental speciation analysis methods of the three metals are followingly reviewed.The chapter ends at the review on the advantages and advances of multi-elemental speciation analysis.In the second chapter,a HPLC-ICP-MS method for simultaneous speciation analysis of arsenic and mercury was developed.A homemade 5 cm reverse phase C18 column with two mobile phases of 4 mM TBAH（pH 6.0）and 20 mM Cys+4 mM TBAH（pH 6.0）was used for the simultaneous separation of four arsenic species（As（III）,MMA,DMA,As（V））and three mercury forms（Hg（II）,MeHg,EtHg）within 11 minutes.Sulfur-containing reagents presented in the mobile phases for the separation of mercury species may retard or even prohibit the elution of As（III）from the C18 column because they may complex with As（III）to to form insoluble As-complexes.To eliminate the interfering effect of Cys on As（III）,4 mM TBAH（pH 6.0）was fed to elute As（III）in the first one minute and then 20 mM Cys+4 mM TBAH（pH 6.0）was introduced to elute other As-and Hg-species in the following 11 minutes.The detection limits of As（III）,MMA,DMA,As（V）,Hg（II）,MeHg,and EtHg were 0.092,0.081,0.078,0.15,0.016,0.027,and 0.032μg L-1,respectively.The reproducibilities（in terms of RSDs）of peak height and peak area were all below 4%.The proposed method was successfully applied to the simultaneous speciation analysis of arsenic and mercury in fresh and dry-powdered lotus root.The contents of DMA and MeHg in all lotus samples were variable in the ranges of 3.5-7.9 and 0.6-1.0μg kg-1,respectively.In the third chapter,we developed a HPLC-ICP-MS method for the simultaneous speciation analysis of arsenic,mercury and lead.By using a 15 cm C18 column and two mobile phases of 2 mM TBAH（pH 5.0）as mobile phase A and 20 mM Cys+2 mM TBAH（pH 5.0）as mobile phase B,four arsenic compounds（As（III）,MMA,DMA,As（V））,three mercuric compounds（Hg（II）,MeHg,EtHg,PhHg）and three lead species（Pb（II）,TML,TEL）was successfully separated within 8 minutes with resolutions better than 1.6 under a gradient elution mode（0-1 min 100%A;1-8 min 100%B;8-10 min 100%A）.The precisions of the four arsenic species,the three mercury species and the three lead species were all below 5%for retention time,and peak height and area.The detection limits of As（III）,MMA,DMA,As（V）,Hg（II）,MeHg,EtHg,PhHg,TML,TEL and Pb（II）were 0.036,0.043,0.13,0.20,0.023,0.025,0.036,0.041,0.0076,0.016 and 0.10 ng mL-1,respectively.At the same time,it was successfully applied to the simultaneous speciation analysis of arsenic,mercury and lead in lotus seeds.The contents of DMA,methylmercury,ethylmercury and trimethyl lead in lotus root and lotus root powder were detected as 19.6-28.2,1.2-4.8,1.2-4.1 and 1.4-2.9μg kg-1,respectively.In the last chapter,we summarize all experimental results,and make a prospect to the further development of HPLC-ICP-MS methodologies for multi-elemental speciation analysis and its future application in environmental,food and biological fields. |
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