PNNL

Abstract

The coupling of the liquid sampling-atmospheric pressure glow discharge (LSAPGD) microplasma to an Orbitrap Fusion Lumos Tribrid mass spectrometer is described as a significant step towards the elimination of isobaric interferences in elemental/isotopic mass spectrometry. The developed setup permits broadband, elemental mass spectra to be easily acquired at a mass resolution (m/?m) of 500,000. A new ion source housing and integrated control system provide enhanced stability and sensitivity of the microplasma ion source in comparison to the previous designs. Detailed evaluation of the ion sampling parameters provided insight into differences with other Orbitrap platforms leading to a 5-fold increase in resolution in elemental/isotopic analysis. The roles of data acquisition/ion processing parameters were evaluated with regards to the precision and accuracy of 235U/238U isotope ratios. Significantly, the precision of those measurements improves as a function of pre-set mass resolution up to a value of 1,000,000, where a precision of 0.086 %RSD is obtained for uranium concentrations of 100 ng mL-1. Analytical response curves (log-log), acquired for the two uranium isotopes at a resolution of 120,000 were linear (R2=0.9969) over more than 5 orders of magnitude, with limits of detection of 1 pg mL-1. Based on 60 ?L injection volumes, this represents a mass of 70 fg 235U. These figures of merit satisfy International Target Values (ITVs) for Measurement Uncertainties in Safeguarding Nuclear Materials set by the International Atomic Energy Agency (IAEA). Page 2 of 33 ACS Paragon Plus Environment Analytical Chemistry 123456789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53