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ULTRAFAST CHEMICAL SEPARATIONS
as supporting electrolytes. A potential of 5 V/cm was applied for 1 to 2 days. They were able to obtain complete separation of parent-daughter mixtures such as strontium-yttrium, barium-lanthanum, and cerium-praseodymium. Schumacher and coworkers have performed extensive research on the application of electrophoresis for the separation of radioactive materials. They reported separation of carrier-free 90Sr-90Y [Sch57] and investigated the effect of a number of chelating agents on the separation of a number of inorganic ions [Sch58]. A number of parent-daughter pairs could be separated in a relatively short time, e.g., yttrium from strontium and lanthanum from barium in 3 min [Sch60]. This technique was used for the analysis of rare-earth mixtures [Fri61]. Pucar and Jakovac achieved electrophoretic separation of rare-earth mixtures using 0.05M lactic acid in 30-min runs [Puc60, Puc62, Jak62]. Use of α-hydroxyisobutyric acid in electrophoresis of lanthanides was reported by Bächmann [Bäc65], where the separation of a mixture of cerium, promethium, and europium was achieved in 30 min. This technique was used by Shukla and Adloff to study the chemical behavior of RaD (210Pb), RaE (210Bi), and RaF(210Po) in different acid media [Shu62a, Shu62b]. Applicability of this technique to achieve separation of actinides has been investigated by several researchers. For example, Kraak and Walz [Kra65] reported electrophoretic separation of americium and curium from a solution containing 0.001M EDTA in a 4-h run, while Bächmann [Bäc66] has reported separation of actinium, americium, and curium from one another, as well as separation of various mixtures of actinides and lanthanides. A summary of electrophoretic radiochemical procedures is available in the radiochemical techniques monograph of Bailey [Bai62].
A number of fast radiochemical procedures using paper electrophoresis are available in the literature; however, such procedures are known only for a few elements, namely, selenium, bromine, strontium, cesium, barium, lanthanum, cerium, and praseodymium. The list of elements and the separation times of procedures are for the separation of a specific lanthanide from fission products. Ohyoshi and coworkers [Ohy72] studied 40-s 144La by separating lanthanum from fission products in about 25 s. They used nitrilotriacetic acid at pH 2.0 as the supporting electrolyte and chromatographic paper as the supporting medium. The irradiated uranium solution, along with lanthanum and cerium carriers, was spotted on the paper wetted with the supporting electrolyte. By applying a potential gradient of 90 V/cm for 70 s, they achieved the separation of lanthanum. Using a similar procedure, but a higher potential gradient (300 to 400 V/cm), Yamamoto and coworkers have achieved separation of lanthanum, cerium, and praseodymium from fission products in 2 to 3 min [Yam80, Yam81].
Table 9. Fast chemical procedures based on electrophoresis.