TOXIC SPECIES IN ENVIRONMENTAL AND BIOLOGICAL SAMPLES

这项研究计划的目标是开发新的方法， 定量测定和痕量形态分析（ppm至ppb） 复杂固体或液体基质中的元素。 元素分布 环境和生物样品已经通过X射线获得 在痕量水平上，通过质子诱导的X射线发射 （PIXE）。 这一分析能力将得到进一步发展， 注意改进样品制备技术。 这种多元素技术将用于重金属的形态分析。 元素 这将通过进行预浓缩和 各种物质的化学分离，例如，四种砷 物种中常见的生物样品，并采用PIXE 确定元素浓度的技术。 替代方法 基于化学反应的动力学控制将探索 砷等元素的形态。 本研究计划的最重要目标是扩展PIXE 能力，包括使用质子微探针（微PIXE）的 测量微观尺寸样品中的元素浓度。 将在100 μ m × 100 μ m的目标区域中确定元素分布， 通过光栅扫描1 μ m × 1 μ m的质子束穿过该目标区域。 将采取预防措施，以尽量减少以下因素的影响导致的样品降解 热和辐射损害。 组织切片和单个组织的元素图谱 细胞将获得与此micro-PIXE系统。

The objectives in this research program are to develop new methods for the quantitative determination and for the speciation of trace (ppm to ppb) elements in complex solid or liquid matrices. Elemental profiles in environmental and biological samples have been obtained by X-ray fluorescence (XRF) and at trace levels, by proton induced X-ray emission (PIXE). This analytical capability will be developed further with special attention being devoted to improving techniques of sample preparation. This multielemental technique will be used for the speciation of heavy elements. This will be accomplished by carrying out preconcentration and chemical separations of the various species, for example, the four arsenic species commonly encountered in biological samples, and employing the PIXE technique for determining the elemental concentration. Alternative methods based on the kinetic control of chemical reactions will be explored for the speciation of elements such as arsenic. The most important objective in this research program is to extend the PIXE capability to include the use of a proton microprobe (micro-PIXE) for the measurement of elemental concentrations in microscopic size samples. Elemental profiles will be determined in a target area 100 mum x 100 mum, by rastering a 1 mum x 1 mum proton beam across this target area. Precautions will be taken to minimize sample degradation by the effects of heat and radiation damage. Elemental maps of tissue slices and single cells will be obtained with this micro-PIXE system.