The mass of the systems in vials was weighed at several points: empty, filled with all components, with the supernatant removed, and dried. By comparing the mass of the systems with the supernatant removed and when dried, we obtain the water content of the PEC. Drying is verified via evaluation of the cobalt colour; hydrated wet cobalt is bright pink, while dehydrated cobalt is dark blue. Sufficient cobalt was present after drying to visually verify successful dehydration.