An inert oil (e.g., silicone oil, mineral oil, immersion oil) intended to be used as a barrier/seal/partitioning agent to minimize or prevent sample carryover and/or evaporation in an in vitro diagnostic assay performed on a clinical specimen (e.g., using a microwell plate), and/or to occupy the space between a microscope slide and a microscope objective lens to remove air and enhance image resolution of the microscope.