Potassium isotopic composition of 7 widely available biological standards using collision cell (CC)-MC-ICP-MS.

The development of collision-cell multi-collection inductively-coupled-plasma mass-spectrometers has revolutionized K isotope geochemistry, improving the sensitivity by over a factor 10 compared to older generation instruments. The application of isotope geochemistry of metals in medical science (isotope metallomics) has shown significant growth in the last few years with respect to the study of metal cycles in the body and/or as diagnostic tools for diseases affecting metal homeostasis. Given the major role that K plays in biology through the preservation of cellular homeostasis itself, the generation of nervous impulses, and the formation of glycogen in the liver, the development of K isotope metallomics is imminent and necessary. To this end, we report the first set of high prevision K isotopic data for numerous widely available biological reference materials, spanning both land and sea animals, as well as various bodily organs (muscle, kidney, liver). Results indicate that land animals are globally enriched in the lighter isotopes compared to the sea animals, and that K isotopes are fractionated by more than 1.5 ‰ between organs (bovine), highlighting that K isotopes could be used to study K cycles within the body. These novel data—and reference materials—could be used for future interlaboratory comparisons.