Reduction of UH+ formation for 236U/238U isotope ratio measurements at ultratrace level in double focusing sector field ICP-MS using D2O as solvent

Abstract

The main factors affecting the accurate and precise determination of 236 U using ICP-MS are instrumental background, the isobaric interference of 235 UH 1 molecular ion on 236 U 1 analyte ions, and the presence of 238 U 1 and 235 U 1 peak tails. An optimized analytical method for attenuating the influence of these factors on uranium isotope ratio measurements at ultratrace level of environmental samples has been developed. In order to reduce 235 UH 1 formation, D 2 O (heavy water) is used as a solvent for the dissolution and dilution of uranium samples. Abundance sensitivity was improved by use of medium mass resolution (m/Dm~4450) in comparison with low mass resolution in double-focusing sector field ICP-MS (ICP-SFMS). For solution introduction the performances of several different sample introduction systems (Meinhard, Aridus and ultrasonic nebulizer) were studied. It has been shown, that for all nebulization systems, a diminution in UH 1 /U 1 is observed in D 2 O as compared with H 2 O as solvent. Optimum results were obtained in ICP-SFMS for a desolvating microconcentric nebulizer system (Aridus) with a minimum hydride formation rate of 9 6 10 27 and a limit for 236 U/ 238 U isotopic ratio measurements of 3-5 6 10 27. A comparison was performed of three commercially available sector field ICP-MS devices, with good agreement found between single collector and multiple collector ICP-MS (MC-ICP-MS).

Determination of U, Th and Pu in natural waters, biological materials and clinical samples by ETV-ICP-MS

“…Despite the ratio UH/U being one order of magnitude lower with ETV than when using solution nebulization, Aridus desolvation or ultrasonic nebulization introduction systems, 25,27,72 in the presence of a 10 ppm solution of U a ratio of 2.5 Â 10 À6 was obtained for UH/U, and the signal for mass 239 corresponding to an equivalent concentration of 0.25 ppt 239 Pu arises. Decreasing interference could be accomplished by column separation 73 or using D 2 Oas the solvent.…”

“…Decreasing interference could be accomplished by column separation 73 or using D 2 Oas the solvent. 25,72 Conclusions A rapid and sensitive method for the determination of U, Th and Pu in natural waters, biological material and urine by ETV-ICP-MS based on Ca 3 (PO 4 ) 2 co-precipitation provides sufficient detection power and throughput to be useful for screening exposed samples and individuals. In addition, the simplified sample preparation procedures used significantly reduce the total analysis time.…”

“…One of the most important components affecting performance by ICP-MS is the sample introduction system. A variety of these has been evaluated for radionuclide detection, including the cross-flow nebulizer, ultrasonic nebulizer, 25,26 desolvation systems, [26][27][28] micronebulizers 29 and electrothermal vaporization (ETV). [30][31][32][33][34][35][36][37] The use of ETV coupled to ICP-MS offers several advantages, including improved transport efficiency (20-80% in contrast to 2-5% using solution nebulization), reduced oxide and hydride formation because the solvent is largely removed, minimal sample consumption (10-100 mL), no waste production and accommodation of complex sample matrices, i.e., salts, organic matrices, solids, strong acids and slurries, with very little sample preparation.…”

Long-Term Effects of Exposure to Low-Levels of Radioactivity: a Retrospective Study of 239Pu and 90Sr from Nuclear Bomb Tests on the Swiss Population

“…Consequently, peak tailing from 238 U + and the formation of 238 U 1 H + molecular interference isobaric to 239 Pu are the limiting factors of plutonium analysis. The hydrogen originates from the water solvent (Zoriy et al, 2004). Because the degrees of ionization of uranium and hydrogen atoms in argon plasma are 100 % and about 0.1 %, respectively, uranium hydride UH + i s f o r m e d i n t h e p l a s m a , m o s t p r o b a b l y t h r o u g h reaction:…”

Comparison of laser ablation, electrothermal vaporization and solution nebulization for the determination of radionuclides in liquid samples by inductively coupled plasma mass spectrometry

“…A variety of solution nebulization (SN) systems, [9][10][11][12] as well as electrothermal vaporization (ETV) [13][14][15][16][17] and laser ablation (LA) 18 techniques have thus been examined, the latter two holding promise of increased detection power because of enhanced sample introduction efficiency and, frequently, lower background arising from molecular ions. In addition, ETV has the ability to use thermal programming, allowing selective removal of sample matrix constituents, thereby eliminating or reducing spectroscopic interferences that would otherwise arise from the matrix.…”