Dear dr Stacy
We have run Rb in our TIMS Thermo MAT-262. We have not seen any problem with deterioration of Faraday cups or any memory problem with TIMS. But there are a few reports in literature which say that efficiency of Faraday cups goes down if you bombard these with large beams of light elements like Rb. There could be memory effects in ICPMS but no such effects will be seen with TIMS.
Hope this gives you confidence in analysing Rb with TIMS.
Dr s k Aggarwal , Mumbai, India
You are welcome to join us at mass spectrometry congress in Lucknow during Nov 28 to 30, 2018 which is being organised by me as the chairperson of this congress .
All the best . Do write if you have any further queries .
Sent from my iPhone
Dr S K Aggarwal, FRSC, Mumbai 9892578865
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> On 06-Jun-2018, at 6:38 PM, Pappas, Richard Steve (CDC/ONDIEH/NCEH) <[log in to unmask]> wrote:
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> 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
> -----Original Message-----
> 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
> (512) 471-6873
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