Study On Determination Of Trace Thiourea Dioxide

Thiourea dioxide is widely used in the recent years. However, there is some disadvantages in determination methods on trace of thiourea dioxide..For example, it is complexity operation and the high cost of reagents. New determination methods of thiourea dioxide were established in this paper, the method of phosphomolybdic blue color system spectrophotometric determination of thiourea dioxide was establishment. And the application of fluorescence analysis was explored on the determination method of thiourea dioxide, which opened other direction for the study of the determination method of thiourea dioxide. The main research contents in the thesis could be summarized as follows:(1) The determination methods of thiourea dioxide and its research status were highlighted comprehensively.(2) The phosphorus molybdenum blue color system of spectrophotometric determination method on trace of thiourea dioxide was established, the optimal experimental conditions were determined, the standard curve was set up and the accuracy and correctness of the method were tested, also the recoveries of some samples were analyzed. The experimental results showed that:the optimal absorption wavelength was710nm, and the optimum quantities of reagents were showed as follows:In the25mL systems,0.01600g·mL-1of sodium dihydrogen phosphate solution0.25mL,0.01600g·mL-1of ammonium molybdate solution2.5mL, and0.15mol·L-1of sulfuric acid solution0.3mL, with a certain amount of thiourea dioxide, at60℃water bath heated for25min.The molar absorption coefficient of this system was obtained:ε=3.057X103L·mol-1·cm-1; The linear regression equation was A=0.00639+0.02812C, the linear range was0.2002～18.02μg· mL-1; Correlation coefficient:r=0.9996; Detection limit was0.1200μg·mL-1. The method was successfully used for the determination of thiourea dioxide in synthetic water samples and lotus seed paste samples, and the recovery rate was95.34%～105.7%. (3) Fluorescence spectrophotometry was applied to determine trace of thiourea dioxide for the first time, a new method for determination of thiourea dioxide was established. The optimal experimental conditions of the new method were determined including the fluorescence instrument measurement conditions, the optimum pH value, the optimal dosage of reagents, the optimal reaction temperature and reaction time, the added order of reagents, and the interference of the interfering ion experiments, etc.; The standard curve was set up and the accuracy of the method was tested, also the recoveries of synthetic water were analyzed. The experimental results showed that: The optimal experimental conditions:Excitation wavelength was280nm, emission wavelength was355nm, in the25mL system, the optimum pH value was9.6, the optimum dosage for0.1000mg·mL-1of nitrobenzene was2mL, with a certain amount of thiourea dioxide was heated in70℃water bath for15min. The linear range of this method was0.06000～1.200μg·mL-1, and the detection limit was3.061ng·mL-1, it could be seen that the sensitivity of the fluorescence analysis methods was so good, and it was much more suitable for the determination of low concentrations of thiourea dioxide. The method could be used for the determination of thiourea dioxide for synthetic water samples, the relative standard deviation was1.11%～2.46%, and the recovery rate was92.00%～106.7%.The results were accurate and reliable.