The New Methods For Hygienic Determination Of Arsenic And Their Application

Chapter 1In order to establish new methods for the determination of trace arsenic in human hair samples by resonance fluorescence technology, a new reaction system of As(Ⅴ) -(NH4)2MoO4-RhB-H2SO4 was selected. The properties of the spectrum of the system were studied. The influencing factors on the strength of the resonance fluorescence including acidity, dosage of the reagents, temperature, reaction time, coexisting ions etc, and the optimum conditions of the reactions in the system were investigated. A new resonance fluorescence method for determining trace arsenic was established, which based on the linear relationship between the system's resonance fluorescence quenching intensity(△F) to the concentration of As(Ⅴ) in solution .The experimental results showed that the maximum resonance fluorescence peak of the RhB in sulfuric acid medium was located at 570nm. Through scanning the three-dimensional fluorescence and the absorption spectrum of the system, the resonance fluorescence spectrum's character was studied. The intensity decreased with adding As(Ⅴ) because of the association reaction of As(Ⅴ) with molybdate and rhodamine B in sulphuric acid medium. The decrease intensity of resonance fluorescence was proportional to the concentration of As(Ⅴ) in the range of 0.05～3.0μg/25mL, and the detection limit was 1.20μg/L. The proposed method could be operated conveniently with high sensitivity and good selectivity. It was applied to the determination of trace arsenic of human hair samples with satisfactory results. The relative standard deviation and the recovery were 1.12%～1.61%and 94.8%~104.6%, respectively. Chapter 2Section 1A new reaction system of As(Ⅴ)-(NH4)2MoO4-IG-H2SO4 for the determination of arsenic in the cosmetics was developed by the RRS method . The properties of the resonance rayleigh scattering spectrum was studied. The influencing factors on the strength of resonance rayleigh scattering including acidity, dosage of the system, temperature, reaction time, coexisting ions etc, and the optimum conditions of the reaction in the system were investigated. The new method which based on the linear relationship between the changing intensity(△I) of the system and the concentration of arsenic with samples in solution was established.The experimental results showed that there was a significant enhance of resonance rayleigh scattering (RRS) intensity in sulphuric acid medium with the association reaction of As(Ⅴ), molybdate and Iodine Green, while the RRS's intensity of the system was weak without the As(Ⅴ) . The maximum resonance rayleigh scattering peak was located at 538nm. The enhanced intensity of resonance fluorescence was proportional to the concentration of arsenic in the range of 0.01～0.4μg/mL, and the detection limit was 1.50μg/L. It was applied to the determination of trace Arsenic of the cosmetic samples with satisfactory results. The relative standard deviation and the recovery rate were 1.86%～2.55% and 95.5%～104.3%, respectively. The proposed method could be operated conveniently with high sensitivity and good selectivity.SectionⅡA new reaction system of As(Ⅲ) -I2-CV-KI-PBS for the determination of arsenic in environmental water samples were developed by the RRS mothed. The properties of the resonance rayleigh scattering spectrum were studied. The influencing factors on the strength of resonance rayleigh scattering including medium, dosage of the system, temperature, reaction time, coexisting ions etc, and the optimum conditions of the reaction in the system were investigated. The method which based on the linear relationship between the changing intensity(△I) of the system and the concentration of arsenic with samples in solution were established.The experimental results showed, when the As(Ⅲ) has not been joined the solution, as I 3? and CV+ formed the ion association complex particles, there were four resonance rayleigh scattering peaks, which were located at 321.8,399.4,532.6 and 629.2nm wavelength, the light scattering intensity at 532.6 nm was largest. And the intensity decreased with the oxidation-reduction reaction of As(Ⅲ) with I2 in PBS. The decreasement of resonance rayleigh scattering intensity was linear to the concentration of As(Ⅲ). The detection limit was 1.00μg/L and the linearity range were 0.1-3.0μg/25mL for the system. This method could be operated conveniently with high sensitivity and good selectivity. When the proposed method was used to determine trace arsenic in environment water samples, satisfactory results were obtained and the relative standard deviation range and the recovery range were 2.35%～3.01% and 96.7%～106.7%, respectively.Chapter 3A new inhibitory kinetics fluorescence method was proposed for the determination of As(Ⅲ) . The new system of As(Ⅲ)-KBrO3-ADR-H2SO4 was developed. The properties of the fluorescence spectra of the system, the influencing factors and the optimum conditions of the reactions were investigated. The mechanism of reaction was studied. A new method for determining trace arsenic was established which based on the linear relationship between the changing intensity of fluorescence(△F=F-F0)and the concentration of Arsenic in solution.The experimental results showed that the maximum fluorescence peak of ADR was located at 550nm in sulphuric acid medium, and the intensity of the fluorescence could be quenched for the potassium bromate oxidizing the ADR. Trace amounts of As(Ⅲ) could inhibit the reaction, which resulted in the increasing of the intensity of fluorescence compared with the blank.The changing intensity of fluorescence(△F=F-F0) was proportional to the concentration of arsenic in the range of 0.015-0.450μg /mL and the detection limit was 2.1μg/L. This method was quick and simple with high sensitivity and good selectivity. It succeeded in the determination of trace arsenic in food products with satisfactory results, and the relative standard deviation and the recoveries range were 2.31%~ 2.83%and 90.0%～107.2%, respectively.