| Flame atomic absorption spectrometry (FAAS) has many advantages, conveniencely and easily to use, good ability on stability and anti-interference. The direct FAAS whose detection limit is mg/L, can not adapt to the determination of ug/L class sample. For this, many separation and preconcentration techniques are studied, such as absorption, complexing and extraction, ion-exchange, liquid membrane preconcentration, precipitation and coprecipitation, etc. These techniques are often used off-line, have many disadvantages: complex operating process, time consuming, the reproductivity of operation can not be controlled accurately. The technique of the Combination of on-line electrochemical preconcentration and flame atomic absorption spectrometry, all processes are carried in a close pipe system, the above problems can be solved and it have other advantages: the preconcentration step can be done without any organic reagent and complex. This technique is of wider foreground for its non-pollution. So far, the studies on this technique are few, the main problem is that the non-reasonable design on the flow through electrochemical preconcentration cell and its limited application, especially on .determination of the elements before hydrogen. The problems will be dissolved by optimization of the design of the cell. Moreover, the mechanism and the application are also discussed in this paper. The dissertation consisted of five chapters.In first chapter: An overview was presented on the on-line preconcentration technique, the solid phase extraction, precipitation and coprecipitation, liquid-liquid extraction, electrochemical preconcentration. Especially, the principles, equipment and the application of electrochemical preconcentration in AAS were described in detail.In second chapter: The process of the flow through electrochemical cell's designing and making was described in detail, including the fabrication of half-electrode; pretreatment of graphite particle; assemblage, seal, pretreatment andtest of the new cell. For good preconcentration efficiency, the graphite particles were used as the electrode material, the geometry structure of the preconcentration cell was cone, which was profitable for the passing of the solution. There was a 1 mm PVC micro-hole board between the work electrode and the assistant electrode which was below the work electrode. A polyethylene pipe whose diameter was 1 mm and length was 40cm connected the cell and the FAAS. The pretreatment and aging process were studied. The performance was evaluated from the geometry structure, capability, life, the diameter and length of pipe etc. Usually the degree of its usage is above 900 times.In third chapter: A method of the combination of on line electrochemical preconcentration and FAAS for determination of Cu2+, Pb2+ Cd2+ Zn2+ was established. The influential factors were studied, including the size and fill-degree of graphite particle, the pH of the preconcentration solution, the kind and concentration of supporting electrolyte and stripping solution, voltage of preconceniration and stripping, flow rate of preconcentraion and stripping, etc. Under the optimized condition, the 20ml soultions of 0.01ug/mlCu2+, 0.1ug/ml Pb2+, 0.05ug/ml Cd2+ 0.05ug/ml Zn2+, their characteristic concentrations were 0.121ug/L, 1.833 ug/L. 0.677 ug/L, 0.420 ug/L, respectively; the RSDS (n=5) were 4.6%. 4.1%. 3.2%. 6.7%. respectively; the enrichment factors were 177, 85, 61, 90. respectively. It was proposed that electrodeposition was the dominant mechanism for the preconcentration of Cu2+ at lower potentials, and the electrosoption also played a role to some degree. On the optimized condition, the possible mechanism was the complex of electrodeposition, electrosorption and electrochemical-hydrate coprecipitation for the preconcentration of Pb2+, Cd2+, Zn2+.In chapter four: The Cu2+, Pb2+, Cd2+, Zn2+ in river water and tap water were determinated by this method and the recovery was in the range of 96.7?105.3%. The results were satisfactory.In chapter five:...
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