| With the development of heavy industry,the geographical location shifts from the city to the suburbs,heavy metal pollution had more and more serious impact on the surrounding environment.At present,the sources of water environment pollution were man-made waste water,waste water from metallurgical and papermaking industries,and illegal leaked sewage from chemical industry.Therefore,it had become an urgent problem for researchers to detect the types and contents of heavy metals in ecological water samples.Solution cathode glow discharge atomic emission spectrometry(SCGD-AES)was a new technology with the advantages of rapid detection,simple operation and real-time monitoring.In recent decades,it had been widely used in the detection of mineral water,rivers and lakes,wine,tap water,industrial wastewater,salt water,blood samples and hair samples.SCGD source had a good application prospect in element determination,but its sensitivity and detection limits(DLs)still need to be improved.This thesis mainly does the following research work:Firstly,an improved SCGD-AES method for the determination of elements was proposed.The effects of temperature characteristics and surface oxide formation rate on the metal anode were studied in the cooling temperature range of 10 °C-30 °C,and the variation of plasma characteristic parameters at different refrigeration temperatures was analyzed.It was found that most of the changes of the above parameters are related to the refrigeration temperature,while the excitation temperature was independent of the refrigeration temperature.The spectral signal of metal elements was enhanced by lowering the surface temperature of metal anode.In addition,the anodic refrigeration method improves the stability of spectral emission of metallic elements.Secondly,DLs of Ag,Cd,Cu,Mn and Zn were obtained by detecting them in the solution with and without refrigeration system(refrigeration temperature 15 ℃).Under the same experimental conditions,the DLs of Ag,Cd,Cu,Mn and Zn were increased by 3.1-6.5 times compared with that of the unrefrigerated system.The determination results of Ag,Cd,Cu,Mn and Zn in standard solution(BWB2446-2016)and real solution samples from the Yangtze River by means of refrigerating anode SCGD source are in good agreement with the reference values determined by inductively coupled plasma atomic emission spectrometry(ICP-AES).The recoveries of water samples in the Yangtze River ranged from 101.5% to 110.0%,which proved that the determination results had high accuracy and reliability.The results show that refrigeration metal anode-SCGD-AES can improve its analytical ability,and provide an alternative analytical method for on-site,real-time and online detection of metal elements in water samples.Then,the cathode structure between the anode and cathode of the discharge plasma was redesigned.The relative parameters of stainless steel and graphite were compared,and the electrical and spectral characteristics of the two materials were studied,and the more suitable material(stainless steel)was finally selected as the subsequent experimental conditions.It is found that the stainless steel cathode structure can reduce the flow rate of solution and increase the bearing capacity of discharge current.Finally,in order to verify the feasibility of the cathode structure,the DLs of K,Na,Ni,Cd,Pb,Co and Hg were analyzed by SCGD-AES method,and the recovery rates of Cd and Ni in spring,river and reservoir water were measured.Then ICP-AES was used to verify the recovery rate.The results show that applying the new material to the new cathode structure is an effective method to improve the detection performance. |
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