Figure 1.

An illustration of the dialysis approach used to measure the concentration of free propofol in the aqueous phase of microemulsion and lipid emulsion propofol. Because their molecular sizes are greater than the molecular weight cut-off (MWCO) of the dialysis tubing, microemulsion and lipid emulsion propofol remain inside the membrane bag, whereas free propofol, which is below the MWCO, escapes into the release medium. After reaching saturation, the concentration of free propofol in a solution of 2.25% glycerine was measured by high-performance liquid chromatography. Lipid emulsion or microemulsion propofol (○); Free propofol (∘)