The Study And Application Of The Descriptive Chemistry Of The Masking Agent In Fast Chemical Analysis

Now in the analytical laboratory of reprocessing plant in England and France, the most of analysis was carried out with auto-analysis installation after a simple sample treatment step. This way can be considered as fast chemical analysis.Using masking agent to eliminate the interference is a very simple and fast way for treatment sample. But to choose a suitable masking agent and the optimal conditions is a real professional work. It depends on the knowledge of the descriptive chemistry of the analyst about the analyte, interferents and masking agent. So to study of the rules followed regularly and exceptions of the masking agent reacting with the analyte and interferents in reprocessing analytical samples, to use the rules solving the specific analytical problem is helpful and useful. So this dissertation is focused in the field of the descriptive chemistry of the masking agent in fast chemical analysis and its application.The principle for selecting masking agent is recommended and a new method for improving the selectivity of masking agent with co-existence ion effect is proposed after studying the descriptive chemistry of the complexants as masking agent.Tree specific analytical problems are studied and three fast chemical analysis methods are established using masking agent to eliminate the interferences of co-existence ions. The established methods are descript bellow.1. The rule of Zn-EDTA masking the prone-hydrolysis ion—A fast analytical method for determining the free acid in reprocessing solution by photo-spectrometry.The prone-hydrolysis ion such as Fe3+, Pu3+, Pu4+, Zr4+, Cr3+etc is the main interference maker for determination of free acid in reprocessing solution. A very special complex Zn-EDTA is chosen as the masking agent. Zn-EDTA reacts with the prone-hydrolysis ions and produces some stable complex of prone-hydrolysis ions and free Zn2+. The reaction doesn't release and consume any H+. The free Zn2+ doesn'thydrolysis in the condition of measurement and has no any absorption at the measurement wave length. Orange yellow IV is used as developer. It is very sensitive for acidity changing. The results of experiments show that the interferences of the prone-hydrolysis ions can be eliminated very effectively by Zn-EDTA. A very simple and fast procedure is recommended for determination of the free acid after carefully studying the measurement conditions. The procedure is used to analysis the free acid in the solution of new process research work for reprocessing. The results are comparable with the results obtained by a typical method of determination the free acid in reprocessing.A flow dilution method is proposed for automatization the method. The rule followed by acidity in dispersion cell is calculated. A new mode for determining the free acid by the dilution time is established. The linear range is 0.7mol/l--2.5mol/l, RSD<0.4% when the concentration of the free acid is about 2mol/l. A remote control installation is installed using the principle of the method. The linear range is G.9mol/l~2.5mol/l, RSD<3% when the concentration of the free acid is about 2mol/l.2. The rule of Zn-EDTA masking the ions from the stainless steel erosion- A fast analytical method for determining the content of uranium in the line of purification of uraniumA new masking and buffer system (Zn-EDTA ~ EDTA) is proposed by studying the rules of EDTA reaction with the analyte (UO22+) and interferents (Fe3+,Zr4+,Cr3+). A system composing of Zn-EDTA and EDTA can be used as masking agent instead of DCTA which is prone-precipitation. And the system also can be used as buffer agent instead of chloroacetic acid and its salt which will erode the stainless steel facilities such as the waste liquid tube.A fast analytical procedure for determination of the concentration of uranium in the line of purification of uranium is established. When the content of uranium between 0.04g/l and 1.5g/l. The procedure can be done with two steps. The acidity of sample in the range of 0.1mo/1—2mol/l have no obvious deference in the analysis results. The procedure is very useful for process control and can be automated easily.3. The rules of 5-Sulfosalicylic acid forming complexes with transition metals ion and actinide series ion— A new method for determination of thealkalis and alkali-earth metal ions in the complicated samples by ion chromatography.According to the descriptive chemistry of 5-Sulfosalicylic acid, it can react with transitional metal ion and actinium family to form complexes, and it can not react with alkalis and alkali-earth metals ions. Using this characteristic of 5-Sulfosalicylic acid, a new method for determination of the alkalis and alkali-earth metal ions in the complicated samples with ion chromatography is established. The RSD is better than 1.7% and 2.1% for determination of sodium and barium respectively. The recovery of the addition method is from 98% to 104% for simulation solution of the high level liquid waste and the real samples.The analysis results of the sodium by this method are comparable with the results obtained by the atomic absorption spectrometry. The procedure and chromatography is much simple and take shorter time.An indirect method for determination of sulfate in the high level liquid waste is established by detecting the barium ion with chromatography. The analysis results arc comparable with the result obtained by anion chromatography. From the work descript above, a conclusion is educed:The knowledge of the descriptive chemistry of analvte. interferents and the masking agents serves as an extremely potent contribution to solving the specific analytical problem and developing fast procedure.