Trace elemental analysis of bulk uranium materials using an inline automated sample preparation technique for ICP-OES

An automated inline method for the separation of trace element impurities from uranium matrices using a 200 µL column packed with UTEVA resin is presented here utilizing an Elemental Scientific, Inc. prepFAST IC in combination with a Perkin Elmer Avio 500 ICP-OES. This method reduces human exposure to highly concentrated acids and uranium-rich samples by automating the chemistry and introduction to the ICP. Calibration standards were prepared using inline dilutions requiring a single stock standard. The separation of trace elements from uranium matrices requires samples to be prepared in 8 M HNO₃, which can be detrimental to the ICP, thus a post-column dilution step was employed to dilute the eluent matrix to 4 M HNO₃. The method was optimized for a sample-to-sample time of < 9 min and monitored 21 elements in total. Proof of concept experiments for 1 µg mL⁻¹ trace elements spiked into 0.1 vol%, 0.5 vol%, and 1.0 vol% uranium matrices resulted in < 5% relative difference and < 10% relative standard deviation for triplicate measurements of each uranium matrix analyzed. Inline dilutions (pre-column) of 2 vol% uranium + 20 µg mL⁻¹ trace elements resulted in accurate and precise measurements using dilution factors of 2× 4× 5× and 20×. Method detection limits for the 21 elements (Al, B, Ba, Be, Cd, Ca, Co, Cu, Fe, Li, Pb, Mg, Mn, Ni, K, Sr, Na, V, Zn, Zr, and U) analyzed for ranged from 7 to 326 ng mL⁻¹ for 70 µL volume injections.