Study On New Methods For High Sensitive Detection Of Heavy Metal Elements In Water Based On Laser Induced Breakdown Spectroscopy

With the development of industry and agriculture and the acceleration of urbanization,large amounts of industrial,agricultural and domestic waste containing heavy metal elements are discharged into water.Therefore,heavy metal contamination of water body is a growing problem.Heavy metal elements in water,which even in small concentrations could be harmful to health through drinking or food chain.Therefore,the detection of heavy metal elements in water is of great significance.In this thesis,laser-induced breakdown spectroscopy(LIBS)was applied to quantitative analysis of Cu,Mn,Cr(?)and Cr(VI)in water in the form of matrix conversion using resins as a new solid-phase support.The specific research contents are as follows:1.LIBS was applied to detect concentrations of Cu and Mn in aqueous solution using chelate resins as a solid-phase support.The parameters,such as laser energy,delay time,laser focus position,flow rate of sample solution for preconcentration and pH of sample solution,were investigated.The quantitative analysis for Cu and Mn was carried out.The linear correlation coefficients of the two elements were 0.993 and 0.991,and the limits of detection were 0.03 mg/L and 0.098 mg/L,respectively.The results show that the detection of Cu and Mn in water can be achieved by using chelate resins as a solid-phase support with high detection sensitivity.Then,natural water samples were obtained to verify the feasibility of the present method and the recoveries were evaluated.The recoveries of Cu and Mn at different concentration levels of natural water samples were in the range of 93.88%-108.09% and 91.99%-103.88%,which indicates that the proposed method is also applicable to the detection of natural waters.Finally,based on the pH adsorption thresholds of Cu and Mn are different,the separation and detection of Cu and Mn was achieved by adjusting the pH value of the mixed solution.2.Chelate resins and anion exchange resins were used as the adsorbents for Cr(?)and Cr(VI),respectively.The valence state separation and LIBS detection of these two elements was achieved.The calibration models of Cr(?)and Cr(VI)were established,and the limits of detection were calculated to be 0.088 mg/L and 0.27 mg/L,the relative errors between predicted values and true ones were in the range of 2.0%-13.5% and4.5%-15.8%,respectively.These results indicate that the limits of detection of Cr(?)and Cr(VI)obtained by the proposed method are rather lower and the accuracy of calibration models is rather higher.In addition,separation of Cr(?)and Cr(VI)in the mixed solution was achieved by the separation and preconcentration.Comparative analysis of the results came from the mixed solution and the single Cr element solution(containing only Cr(?)or Cr(VI))was carried out and the relative errors ranged from 2.98% to 13.93%.It shows that the separation and detection of Cr(?)and Cr(VI)can be achieved by the sample pretreatment method proposed in this thesis.