Greenberg R R, Gallorini M, Gills T E
Environ Health Perspect. 1979 Feb;28:1-4. doi: 10.1289/ehp.79281.
Radiochemical neutron activation analysis (RNAA) has been routinely used at the National Bureau of Standards to analyze Cd in a variety of environmentally important matrices. The method used to separate Cd from other neutron-activated products is solvent extraction. Zinc diethyldithiocarbamate [Zn(DDC)2] in chloroform will quantitatively extract Cd from an aqueous solution over a pH range from 1 to 12. In addition to the extraction of Cd, Zn(DDC)2 will also extract Cu, which can interfere with the Cd analysis by producing a high background level of radiation. This can be avoided by first extracting with Bi(DDC)3 in chloroform which removes Cu, but not Cd. Copper concentrations can, therefore, be determined in addition to Cd. This two extraction radiochemical separation procedure is very versatile and is often used as part of a larger multi-element analysis scheme. One such scheme involves the use of an inorganic-ion exchanger, Hydrated Manganese Dioxide (HMD), to retain As, Sb, Se, and Cr prior to extraction. The eluted fraction is then extracted with Bi(DDC)3 to remove Cu, and then with Zn(DDC)2 to remove Cd.
放射化学中子活化分析（RNAA）在美国国家标准局已被常规用于分析各种对环境重要的基质中的镉。从其他中子活化产物中分离镉所使用的方法是溶剂萃取。二乙基二硫代氨基甲酸锌[Zn(DDC)₂]在氯仿中能在pH值1至12的范围内从水溶液中定量萃取镉。除了萃取镉之外，Zn(DDC)₂还会萃取铜，而铜会通过产生高背景辐射水平干扰镉的分析。这可以通过先用三乙基二硫代氨基甲酸铋[Bi(DDC)₃]在氯仿中萃取来避免，Bi(DDC)₃能除去铜但不会除去镉。因此，除了测定镉之外还可以测定铜的浓度。这种两次萃取的放射化学分离程序用途非常广泛，并且经常作为更大的多元素分析方案的一部分使用。一种这样的方案涉及使用无机离子交换剂水合二氧化锰（HMD），在萃取之前保留砷、锑、硒和铬。然后用Bi(DDC)₃萃取洗脱馏分以除去铜，接着用Zn(DDC)₂萃取以除去镉。
