Study Of Electrochemical Vapor Generation Of As And Chemical Vapor Generation Of Cd

The sample introduction technique is always the research focus in atomic spectral analysis method. In this thesis, the basic principle of atomic spectral detection technique was briefly introduced first, then the advantage and disadvantage of a variety of existing sample introduction techniques was mainly introduced. The principle, application and development trend of electrochemical vapor generation technique had been summarized, and the research work of electrochemical hydride generation technique of cadmium and electrochemical vapor generation technique of arsenic had been carried out. The content mainly included three aspects. First is the different behavior of As3+, As5+, MMA(methyl arsenic) and DMA(dimethyl arsenic)on the electrochemical vapor generation at the modified electrodes. Second is the optimization of various experimental parameters and the research on new chemical vapor generation system of cadmium, etc. Third is the analysis of a variety of biological and environmental samples.First of all, we examined the vapor generation efficiency of cadmium in different generation systems, and discovered that using Fe2+-L-Cys-CH3 COOH system could significantly improve the vapor generation efficiency of cadmium, which could achieve more than 4 times of the efficiency of traditional thiourea-Co2+system under the same conditions. And the addition of DDTC could significantly reduce the interference of ions such as Cu and Pb, which basically realized the improvement of generation efficiency and enhancement of anti-interference performance of the method simultaneously. Under optimal experimental conditions, the detection limit of Cd was 0.02 μgL-1, the relative standard deviation was 4.5%(n=11), and the recovery rate was 91.4%~112.2%.Subsequently, the electrochemical vapor generation behavior of arsenic in different valent was studied by using the laboratory homemade threaded electrolytic cell with modified electrode. The result indicated that not only was the atomic spectral signal of As3+ and As5+ at L-Cys/GE electrode significantly enhanced(about 2-3 time of that at graphite electrode), but also signals of the two were equivalent; but when GSH/GE was used as electrodes, there is not any As5+ signal under the same optimized conditions. According to this result, the new method for examining arsenic of different valence forms based on EVG-AFS of modified electrode was firstly established. Through optimizing a variety of experimental parameters, detection limits of the method were 0.28μg L-1 and 0.35μg L-1 respectively, relative standarddeviations were 5.7% and 6.3% respectively, recovery rate were 89.1%~110.6 % and92.8%~107.5 % respectively. This method was featured by high sensitivity, precision and accuracy, and strong anti-interference performance, etc, which could replace traditional chemical vapor generation technique. We also successfully determinated arsenic in multiple environmental samples using this method.Finally, based on the analysis of valent state arsenic, we did systematic research on electrochemical vapor generation behavior of arsenic in different forms with modified electrode, and discovered that, MMA and DMA could be effectively reduced at the GSH/GE with formic acid as cathode electrolyte, while in the medium of H2SO4,only MMA could generate signals, and based on this we could detect arsenic in different forms with EVG-AFS of modified electrode. This method was featured by high sensitivity, precision and accuracy, and strong anti-interference performance,etc.