Concomitant ion effects on isotope ratio measurements with liquid sampling – atmospheric pressure glow discharge ion source Orbitrap mass spectrometry

• Published in: Journal of analytical atomic spectrometry 2018-01, Vol.33 (2)
• Main Authors: Hoegg, Edward D., Marcus, R. Kenneth, Hager, George J., Hart, Garret L., Koppenaal, David W.
• Format: Article
• Language: English
• Subjects: atmospheric pressure sampling; isotope ratio; isotope ratio analysis; isotope ratio measurements; liquid sampling-atmospheric pressure glow discharge; mass spectrometry; Orbitrap; orbitrap mass analyzer; uranium
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/C7JA00308K

RATIONALE: The field of highly accurate and precise isotope ratio (IR) analysis has been dominated by inductively coupled plasma and thermal ionization mass spectrometers. While these instruments are considered the gold standard for IR analysis, the International Atomic Energy Agency desires a field deployable instrument capable of accurately and precisely measuring U isotope ratios. METHODS: The proposed system interfaces the liquid sampling – atmospheric pressure glow discharge (LS-APGD) ion source with a high resolution Exactive Orbitrap mass spectrometer. With this experimental setup certified U isotope standards and unknown samples were analyzed. The accuracy and precision of the system were then determined. RESULTS: The LS-APGD /Exactive instrument measures a certified reference material of natural U (235U/238U = 0.007258) as 0.007041 with a relative standard deviation of 0.158% meeting the International Target Values for Uncertainty for the destructive analysis of U. Additionally, when three unknowns measured and compared to the results from an ICP multi collector instrument, there is no statistical difference between the two instruments.CONCLUSIONS: The LS-APGD / Orbitrap system, while still in the preliminary stages of development, offers highly accurate and precise IR analysis that suggest a paradigm shift in the world of IR analysis. Furthermore, the portability of the LS-APGD as an elemental ion source combined with the low overhead and small size of the Orbitrap suggest that the instrumentation is capable of being field deployable.With liquid sampling glow discharge-Orbitrap MS, isotope ratio and precision performance improves with rejection of concomitant ion species.