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General Spectroscopy - Alkali metals (rubidium) analysis by AA and ICP-OES

 
We normally analyse rubidium (Rb) using our flame AAS but that broke down a couple down a couple of weeks ago and it looks like it will be offline for a while yet. So I'm trying to develop a method for rubidium analysis using ICP-OES. However, I'm finding that the results of the samples and QCs that I've run are significantly higher than the results that were produced previously on the AAS. I was told by the AAS technician that potassium is dosed into the calibration standards as an ionisation suppressant. So I'm wondering if I need to do this as well with my calibration standards? And is there anything else that I should consider that will make this method feasible?The samples that we analysing are predominantly brines from geothermal power stations. We do have an ICP-MS and the method development that I have done for rubidium analysis has been very successful. However, I have to dilute the samples 1000x in order to dilute out the sodium and silica, but this dilutes the rubidium to roughly 1ppb. So ideally I would prefer to use a method on the ICP-OES so that I can run the samples without any dilution.
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admin Total posts: 529
Ionization effects for alkali metals can be significant in ICP applications, and we discuss some details on our website (http://inorganicventures.com/samples-containing-lithium-sodium-potassium-rubidium-or-cesium). Using an ionization buffer can help, and we recommend a Cs ionization buffer for axial view ICP measurements to help with determinations of lighter alkali metals. The Cs is added to both calibration and sample solutions at a concentration of ~500 ppm, and this approach should help with the Rb measurements.
Posted: 09/04/18 21:56:59

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