Good morning, Staci,
Since you are analyzing rocks, I imagine Rb concentration will be significant if not high.
I have used Element 1, 2, XR, not NU Isoprobe, but I have been able to include Na and K in my mass calibration method without nominally having them in my mass calibration solution ever since my first urine analysis. I can see Rb and Cs at lower intensities as well. When run at significant concentrations, the alkali metal guests do seem to overstay their welcome. One can replace the extraction lens on the Element, pull the torch and injector, rinse them in dilute acid followed by ultrapure water, clean cones in dilute acid, replace pump tubing if used. This will decrease the alkali metals levels, but you may still see the remnants around for quite a while. It would depend on the concentration of the enriched isotope relative to what the instrument normally sees.
I don't know about potential for poisoning the Faraday cups. I have not run anything high enough to need to use the cup on our XR.
R. Steven Pappas, Ph.D.
Team Lead, Tobacco Inorganics Group
Centers for Disease Control & Prevention
4770 Buford Highway, NE
M.S. F44, Building 110
Atlanta, GA 30341-3717, USA
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). <[log in to unmask]> On Behalf Of Staci L Loewy
Sent: Tuesday, June 5, 2018 5:43 PM
To: [log in to unmask]
Subject: Rb in mass spec
Has anyone had issues either with Rb memory effects or cup poisoning from running Rb on TIMS or ICP?
We are discussing among our research group about running spiked Rb for Rb-Sr geochronology in our new Nu Plasma 3D MC-ICP-MS. We had such horrific experiences with memory effects with our Isoprobe MC-ICP-MS over the years that we are a little hesitant to move forward without evidence that it will not be a problem. Several folks in our group have expressed concerns that residual spiked Rb in the machine could interfere with the 87Rb correction for subsequent 87Sr analyses as the correction requires the assumption of a natural Rb isotope ratio to make the correction. Others are concerned with the ease of Rb ionization such that introducing Rb into the mass spec would "poison the cups" and produce phantom signals as the Rb re-ionizes during subsequent analyses. Has anyone experienced either of these problems or others from running spiked Rb in a modern TIMS or MC-ICP-MS? We are looking for observations allay our concerns.
As folks have (and still do) run Rb on both TIMS and ICP, I am sending this to both plasmachem and TIMS listservers.
Dr. Staci Loewy
Isotope Geochemist and
MC-ICP-MS Laboratory Manager
The University of Texas at Austin
Department of Geological Sciences
2275 Speedway, Stop C9000
Austin, TX 78712-1722
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