Characterizing noninvasively conservation status of historical wet collections using spatially offset Raman spectroscopy

Fluid-preserved specimens are central to the scientific and cultural value of natural history collections, yet their conservation is challenged by chemical and physical instabilities of both the specimens and their preservation media. Here we report the application of handheld spatially offset Raman spectroscopy (SORS) to noninvasively characterize historical specimens from their conservation status perspective. This goes beyond previously reported basic determination of the major constituents of preservation fluids by providing detailed chemical information on minor dissolved components, such as lipids, protein fragments, and residual fixation products, as well as organic deposits on container walls. This provides insight into fluid degradation, leakage, and specimen-fluid interactions of sealed wet collection items. Furthermore, we demonstrate the capability of directly probing specimen composition. All measurements were performed <i>in situ</i> without opening containers, demonstrating the robustness and versatility of SORS for comprehensive monitoring wet collection status under museum conditions and offering curators actionable insights into degradation processes and long-term collection integrity.