Preparation of β-carotene nanoparticles using supercritical CO2 anti-solvent precipitation by injection of liquefied gas feed solution

Abstract

This study proposes to further exploit the potential of the carbon dioxide supercritical anti-solvent precipitation (SAS) process by using liquefied gas as a feed solvent in the SAS process. In this study, liquefied dimethyl ether (DME) is compared to conventional ethyl acetate as the feed solvent for β-carotene. DME is a gas in its standard state, and when it is made into a subcritical liquefied gas, it has a larger self-diffusion coefficient and saturated vapor pressure, and smaller viscosity and surface tension than liquid solvents. Because of these characteristics of liquefied DME, liquefied DME prevents primary particle agglomeration and DME residue. When ethyl acetate was used as the feed solvent, the conditions giving the smallest particles were 60 °C and 12 MPa, and 31 ± 5 nm primary particles of β-carotene were obtained. However, most of these were aggregated into secondary particles of several hundred nanometers. In the case of liquefied DME, the condition giving the smallest particles was 40 °C and 12 MPa, and primary particles of 58 ± 8 nm β-carotene were dispersed without aggregation. Furthermore, FT-IR analysis detected residual ethyl acetate in the aggregated β-carotene particles, whereas DME was not detected in the dispersed particles. Liquefied DME is likely to be a suitable solvent for the micronization of heat-sensitive substances using the SAS method without agglomeration. Combining various liquefied gases, not just DME, with the SAS process may create possibilities for applying the SAS process to target materials that are insoluble in conventional liquid solvents and for synthesizing even finer nanoparticles.

Keywords

• Antisolvent
• Carotenoid
• Micronization
• Subcritical fluid
• Supercritical fluid