Direct Measurement of Uranium Isotopic Ratios in Soils by Glow Discharge Mass Spectrometry

Abstract

Since the current methodology mandated by the environmental protection agency (EPA) for the determination of isotope ratios of priority metals in sediments, sludges, and soils is both time consuming and labor intensive, it would clearly be of great value in environmental surveys if there were a procedure capable of direct analysis of these materials with little or no sample preparation. A method that holds promise in this regard is glow discharge mass spectrometry (GDMS). GDMS has several characteristics that make it worthy of evaluation; essentially all elements are amenable to analysis, preliminary results indicate isotopic biases are small, and the determination of isotopic ratios at the sub-ppm level is a reasonable hope since detection limits are in the sub-ppb range. Furthermore, previous studies have indicated that GDMS is a fairly precise method for providing isotopic information with good precision; precisions better than 0.05% relative standard deviation (RSD) have been obtained.