Stable isotope analysis has become a widely used biogeochemical tool owing to its capacity to reveal predator foraging habitats, trophic level, and prey preferences. The breadth of applicable tissue types is quickly growing across taxa, including for elasmobranchs, with tooth isotopes gaining traction to trace within-individual variation in trophic ecology. Jaws in museums and private collections present a unique opportunity to access samples from rare or protected species and size classes. However, most of these jaws are chemically treated to prevent degradation and to whiten teeth and cartilage for aesthetic and long-term display. Prior to using stable isotopes from these jaws, we need to understand the impacts of chemical treatments on carbon, nitrogen, and sulphur isotopes. We compared the tooth preparation process (acid digestion) and δ