Chemical Stability and Compatibility - Gold (Au) and tantalum (W) ppb standards
I have a question for you or your technical team. Does Inorganic Ventures know of or heard of any issues with solutions of low-level Gold and Tantalum?
We diluted the a standard 100,000x volumetrically so that the final concentration of the standard was 0.01 ug/L preserved in 2% HNO3 . When we ran that standard on an ICP-MS we got good recoveries (within 20% of target) for all analytes except Gold (recovery was ~30%).
With only a 100x dilution of the standard (final conc. 10ug/L) recoveries were within 10% of the target except for again Gold at 57%.
With only a 2x dilution (final conc. 500ug/L) all analyte recoveries including Gold were good at ±10%.
I am pretty sure this is some form of interference related to ICPMS analysis rather than an solubility/stability issue of the standard but I would still like to check. Thank you.
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Regarding tantalum, low level W is not stable in 2% HNO3 long term. It will adhere to plastic within days. To increase stability, trace amounts of HF are required to prevent this issue, but you may still experience recovery issues. For gold that same phenomenon occurs at all concentrations in HNO3. Our experience is that any level of gold will require HCl (~1% v/v or greater) to remain stable long term. You may want to review this link for more information regarding low level stability. https://www.inorganicventures.com/part-billion-stability-study. |