文摘
A thermodynamic analysis is developed to interpret the influence of temperature and pressurein the production of solid lipid nano- and microparticles by a high-pressure technique namedparticle from gas-saturated solution (PGSS). The pressure-temperature charts show threeregions above the P-T solid-liquid-fluid coexistence curve, from which sub-cooled solid, solid-liquid, or liquid products can be obtained. The relation between the initial and finalthermodynamic properties of the PGSS process were calculated by solving simultaneously theenergy balance and a proper equation of state. The expansion of high-pressure CO2-lipidsaturated solution through the micrometric nozzle was represented by a transformation atconstant total enthalpy. To represent the equilibrium and thermodynamic behavior of CO2-lipid systems the perturbed-hard-sphere-chain theory (PHSCT) was used. As examples, CO2absorption isotherms in lipids and residual properties of high-pressure tristearin-CO2 andtristearin-phosphatidylcoline-CO2 systems were calculated. Enthalpy of fusion of puresubstances and formation enthalpy of microparticulate PGSS products were measured bydifferential scanning calorimetry (DSC). Pure lipid EOS parameters were estimated by a groupcontribution method, whereas the equation of state (EOS) interaction parameters were adjustedon the experimental melting point data under CO2 pressure, measured in a high-pressurewindowed cell. Application of operative charts provides useful information in understandingthe influence of temperature and pressure on the final properties of lipid particles produced byPGSS.