The Solvent Trap cover and Solvent Trap geometry work in concert to create a thermally stable vapor barrier, virtually eliminating solvent loss during the experiment. The geometry includes a reservoir that is filled with a very low viscosity oil or the volatile solvent present in the sample. The Solvent Trap cover includes a blade that is placed into the solvent contained in the well without touching any other part of the upper geometry. A uniform temperature, saturated vapor, environment is established, preventing loss from the sample and condensation from the cover. The Solvent Trap sits directly on a centering ring at the top of the APS surface for easy positioning.