Lead isotope tracing issues

Hi all,

Currently using an old ICP-MS 7500 to do Pb isotope tracing in soils. Ran some data, but strangely the results it has given were much greater than the mainstream literature. The dissolved NIST 981 was even shifted in its values. Here are some of the results I have through excel. Specifically 208/206, and 208/204. The NIST also is shifted, and I'm not sure what I am doing incorrect. Is it something to do with background file usage, interference equations, mass bias correction, or something else. ALl of my data has this similar trend, and my standards have been accurate. It's just the isotopes values all seem shifted, and the totals do NOT reflect relative abundance if that's what the different isotope totals are.

Thank you,

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