Screening design of experiment applied to the supercritical antisolvent precipitation of quercetin

• Quercetin precipitation have been successfully carried out by SAS process.
• A design of experiments at two levels has been successfully applied.
• Nano or microparticles have been obtained in the process.
• The negligible and stronger effects on particle size were identified.
• Crystallinity and activity of quercetin were practically unaltered in the process.

A fractional factorial design of experiment at two levels has been applied to the micro- and nanoprecipitation of quercetin by a supercritical antisolvent process (SAS) in order to identify the factors that are important and their appropriate ranges with the mean particle size used as a response. The model was successfully fitted by multiple linear regressions. In general, higher pressures and temperatures, a lower initial concentration of the solution, and high CO2/liquid solution flow rate ratios favored the precipitation of smaller particles. The use of a smaller nozzle diameter led to smaller particle sizes in the assayed range but washing time had a negligible effect. The morphologies of the precipitates were analyzed by scanning electron microscopy (SEM). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were employed to evaluate the possible loss of crystallinity and activity of the precipitates. Dynamic light scattering (DLS) and image analysis software were used to measure the particle size and particle size distribution. The particle size range of the precipitates was 0.15–1.24 μm and the formation of nanoparticles or microparticles was dependent on the operating conditions of the SAS process. The dynamic light scattering measurements gave higher than expected particle sizes due to possible agglomeration.

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