Determination of technetium-99, thorium-230 and uranium-234 in soils by inductively coupled plasma mass spectrometry using flow injection preconcentration

Abstract

A new method is described for the determination of ⁹⁹Tc, ²³⁰Th, and ²³⁴U at ultra-trace levels in soils. The method used flow injection (FI) for on-line preconcentration of ⁹⁹Tc, ²³⁰Th and ²³⁴U prior to detection using inductively coupled plasma mass spectrometry (ICP-MS). The FI-ICP-MS method results in greater sensitivity and freedom from interferences compared with direct aspiration into an ICP mass spectrometer. Detection limits are improved by approximately a factor of 10. The FI-ICP-MS method is also faster, less labour intensive and generates less laboratory waste than traditional radiochemical methods. The accuracy of the method was tested for ⁹⁹Tc by comparison to liquid scintillation counting and for ²³⁰Th and ²³⁴U by analysis of a US Department of Energy reference soil. Detection limits in the soil for ⁹⁹Tc, ²³⁰Th and ²³⁴U were 11 mBq g^–1(0.02 ng g^–1), 3.7 mBq g^–1(0.005 ng g^–1) and 0.74 mBq g^–1(0.003 ng g^–1), respectively. Sample preparation, analysis protocol, and method validation are described.