Plutonium determination in mineral soils and sediments by a procedure involving microwave digestion and extraction chromatography

A reliable and fast procedure with minimum waste generation for plutonium d etermination in soils and sediments is proposed. The procedure combines mic rowave-assisted digestion for sample dissolution, extraction chromatography for chemical separation, and coprecipitation and alpha-spectrometry for ac tivity measurement. The work is focused on optimisation of the attack and s eparation steps. The microwave-assisted pre-treatment with mixtures of BF-H NO3 and HF-HClO4 achieved total mineralisation of samples in 2 h and 30 min . For the separation step, the influence on actinide chemical recovery of s everal ions usually present in soil and sediment matrices, particularly tri valent iron, were studied. The potential reusability of the chromatographic resins was also evaluated and, in spite of the preservation of plutonium r ecovery and selectivity, some memory effects in consecutive analysis were n oticed. The column obstructions during the separation process were solved b y using a peristaltic pump. Good accuracy, long-term repeatability (CV 6-7% ) and minimum detectable activity (0.11-0.35 Bq kg(-1)) for the proposed pr ocedure were obtained by analysing Pu-238 and Pu239+240 in the sediment CRM IAEA-135. (C) 2001 Elsevier Science B.V. All rights reserved.