Determination of actinide elements at femtogram per gram levels in environmental samples by on-line solid phase extraction and sector-field-inductively coupled plasma-mass spectrometry

Abstract

An on-line solid phase extraction method has been developed for the determination of 232Th, 237Np, 238U, 239Pu, 240Pu, 241Am and 243Am in biological certified reference material using a column containing TRU-Spec™ resin coupled with sector-field inductively coupled plasma-mass spectrometry. Absolute detection limits were 0.7, 0.85, 0.6, and 0.65 fg for 237Np, 239Pu, 241Am and 243Am, respectively. The 239Pu was determined in NIST Human Liver (963±297 fg g −1 compared with a certified value of 848±161 fg g −1) using a dry and wet ashing sample preparation method, and in a spiked cabbage reference material (394±54 fg g −1 compared to an indicative value of 467 fg g −1) using microwave digestion. Sequential separation of Pu and U was achieved by on-column reduction of Pu with titanium(III) chloride and elution in 4 M HCl to facilitate the determination of 239Pu in samples containing high levels of 238U, thereby eliminating the interference of 238U 1H + at m/ z 239. The sequential elution procedure was used to determine 239Pu in NIST human lung (814±55 fg g −1 compared with a certified range of 227–951 fg g −1) and NIST Rocky Flats Soil (2423±137 fg g −1 compared with a certified value of 3307±248 fg g −1).