Technical Questions Forum
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Sample Recovery- Open-cup evaporation
Stability of diluted standards
In our preparation for ICP-MS analysis of USP <232> elements, we perform an intermediate dilution of a 14 element blend. This is a 1:20 dilution to give concentrations (ug/mL, ppm) as follows: Cu = 65, Ni = 30, Mo = 9, V = 6, Cd = 0.25, Hg = 0.75, Pb = 0.25, As = 0.75, Ir = 5, Pd = 5, Pt = 5, Rh = 5, Ru = 5, Co = 2.5. I have viewed information at http://inorganicventures.com/stability-elements-ppb-concentration-levels, which has pointed me in the right direction and is the kind of information I’m looking for, except that our intermediate is at much greater concentrations. I am wondering if you can provide any information regarding the stability of this solution in a 5% nitric acid (HNO3), 1% hydrochloric acid (HCl) solution? If possible, I'm also interested in stability information for a 10 ug/L (ppb) mixture of In, Bi, 6-Li, Y, Sc, and Tb in 3% HNO3.
Stabilizing Si with HF and acid digestions
I recently ordered a 1000 ppm standard of SiO2 for testing on my MP-AES. The label on the standard says there is trace amounts of hydrofluoric acid; does this help the Si stay in solution? If so, are you aware of how accurate an acid digestion for Si would be without the use of HF?