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为了采用~(129)I进行地质定年研究,该类样品中的~(129)I/~(127)I原子比值通常低于10~(-12),因此低的~(129)I流程空白是分析地质定年样品的前提条件之一。在全球范围内,大气中~(129)I的水平呈现显著变化趋势,~(129)I/~(127)I原子比值范围在10~(-10)到10~(-6)。然而,在样品制备过程中,是否大气中的~(129)I会影响流程空白尚未可知。本研究调查了三种常用的~(129)I分析方法,包括直接沉淀法、溶剂萃取法和管式燃烧法(分别以压缩空气和氧气作为载气)来比较流程空白中的~(129)I/~(127)I比值。研究结果表明:在最佳实验室条件下,流程空白均被控制在较低的水平,可用于分析各种环境和地质样品。另外,通过研究溶液的长时间储存,发现当0.4 mol?L~(-1)Na OH溶液储存一年以上时,~(129)I/~(127)I比值比新配制的Na OH溶液有所提高,但基本在实验室正常本底2×10~(-13)以内。采用压缩空气作为载气的管式燃烧法比氧气为载气时具有明显提高的~(129)I/~(127)I比值。研究表明样品和试剂的储存,以及制样过程中与大气的交换程度均会影响流程空白中~(129)I的水平。因此在分析超低~(129)I含量的地质样品时,固体样品中碘的分离应采用低本底的分析方法(如以纯气体作为载体的管式燃烧法),如有必要还可在低大气~(129)I水平的实验室进行实验。
The ~ (129) I / ~ (127) I atomic ratio in this sample is usually less than 10 ~ (-12) for ~ (129) I geo-dating. Is one of the prerequisites for analyzing geologic dating samples. Globally, the level of ~ (129) I in the atmosphere shows a significant trend. The atomic ratio of ~ (129) I / ~ (127) I ranges from 10 -10 to 10 -6. However, it is not clear whether ~ (129) I in the atmosphere affects the process flow during sample preparation. This study investigated three commonly used (129) I analytical methods, including direct precipitation, solvent extraction, and tubular combustion (using compressed air and oxygen as carrier gases) I / ~ (127) I ratio. The results show that: under the best laboratory conditions, the process of the blank are controlled at a lower level, can be used to analyze a variety of environmental and geological samples. In addition, the long-term storage of the solution showed that the ~ (129) I / ~ (127) I ratio was higher than that of the freshly prepared NaOH solution when the 0.4 mol? L ~ (-1) NaOH solution was stored for more than one year Increased, but basically in the normal laboratory background 2 × 10 ~ (-13) or less. The tubular combustion method using compressed air as the carrier gas has a significantly higher value of ~ (129) I / ~ (127) I than oxygen as the carrier gas. Studies show that the storage of samples and reagents, and the degree of exchange with the atmosphere during sample preparation, can affect the level of ~ (129) I in the process blank. Therefore, in the analysis of ultra-low ~ (129) I geological samples, the separation of iodine in solid samples should be based on a low background analysis (eg, tubular combustion with pure gas as a carrier) and low Atmospheric ~ (129) I level laboratory experiments.