Hello,
I measure pure Sb-solutions (KSb(OH)6 dissolved in double-deionized water and adjusted to 2% HNO3 + 0.1% tartaric acid) at the ICP-OES (50-100uM) and at the ICP-MS (0.1-1uM). I get always concentrations higher than they should be. It is typically in the range of 3-10%.
I checked the weighing machine, the flask, the pipette uncertainty. I used different standard-solutions and Sb-salts. I prepared the standards series very carefully. My measured blanks are free of Sb, so no contamination from the devices itself.
However, I am not able to find the weak point. Could tartaric acid effect the sensitivity for OES/MS - measurements? Measured K from the same stocksolution shows also 5% higher concentration at the OES. However, I do not have this problem for other elements/salts in just 2% HNO3.
Dear Sascha Wilke thank you for asking this interesting technical question. Being a synthetic chemist I'm certainly not a proven expert in analytical chemistry. As a hydroxo complex, the compound K[Sb(OH)6] forms basic solutions in water. Thus I assume that the addition of nitric acid is essential to keep all antimony in solution. For a potentially useful detailed study of the determination of antimony by ICP-OES please have a look at the following interesting link:
Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining
Article Determination of traces of Sb(III) using ASV in Sb-rich wate...
According to this study, the addition of tartaric acid serves the purpose of stabilizing the Sb-containing solutions for several days. If this is not necessary and the solutions are analyzed right away, stabilization with HNO3 alone should be sufficient.
I hope this helps. Good luck with your work!
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