Are double spike isotopic standards suitable for quantification by isotope dilution mass spectrometry?

Question

I would like to apply isotope dilution mass spectrometry (IDMS)* to quantify lead at trace levels. A good spike solution for the process would be the NIST SRM 991 which is an enriched material of almost only lead-206, but this material is now discontinued and the replacement is a radioactive material NIST SRM 983, which I think, will be a little difficult to import.

The NRC of Canada has produced the lead-204 and lead-207 double spike isotopic standard BLED-1 which contains 49% and 33% the two isotopes, respectively, and I was wondering if it could be suitable for IDMS considering that the natural relative abundance of those isotopes is low. I have only performed IDMS using the (single spike) NIST SRM 991, and although I think the same IDMS equations will apply to each pair of isotopes, would like to know please if there is something I am not taking into account.

*) An overview about this technique is provided by Vogel, J.; Prizkow, W. Isotope dilution mass spectrometry — A primary method of measurement and its role for RM certification. MAPAN 25, 2010, 135–164, doi 10.1007/s12647-010-0017-7. The author's copy on ResearchGate.

Answer 1

Yes, I think it would be suitable, although I am not an expert in IDMS either. It seems like the new standard contains two stable isotopes. This should give you a built-in check on the data you collect: if you treat Pb-204 as the spike isotope, and calculate the concentration of Pb in your sample from it, you should get the same (or very similar) answer as if you treat Pb-207 as the spike isotope.