Determination of long-lived actinides in soil leachates by inductively coupled plasma: Mass spectrometry

Inductively coupled plasma -- mass spectrometry (ICP-MS) was used to concurrently determine multiple long-lived (t1/2 > 104 y) actinide isotopes in soil samples. Ultrasonic nebulization was found to maximize instrument sensitivity. Instrument detection limits for actinides in solution ranged from 50 mBq L-1 (239Pu) to 2 μBq L-1 (235U) Hydride adducts of 232Th and 238U interfered with the determinations of 233U and 239 Pu; thus, extraction chromatography was, used to eliminate the sample matrix, concentrate the analytes, and separate uranium from the other actinides. Alpha spectrometric determinations of 230Th, 239Pu, and the 234U/238U activity ratio in soil leachates compared well with ICP-MS determinations; however, there were some small systematic differences (ca. 10%) between ICP-MS and a-spectrometric determinations of 234U and 238U activities