Chiral separation performance of micrometer-sized monodispersed silica spheres with high protein loading.

Micrometer-sized monodispersed silica spheres (approximately 360 microm) with high loading of bovine serum albumin (BSA) (approximately 450 mg/g) were prepared as an adsorbent for large-scale chiral separation. The new adsorbent was characterized with scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherms, the mercury intrusion method, infrared spectroscopic analysis, and elementary analysis. The extent of chiral separation was tested with rac-tryptophan (rac-Trp) and rac-phenylalanine (rac-Phe) as solutes. The results showed that the absorbent exhibited a high surface area, large pore volume, and bimodal macromesoporous structures, enabling fast mass transfer and high separation efficiency. A fast adsorption rate, reaching equilibrium in less than 6 min, and a high degree of chiral separation, with the enantiomer excess (e.e.) value reaching as high as 100% in the first 10 min, was observed in a small (5 cm in height, 0.46 cm in internal diameter) packed column that could be regenerated with a pH 5.0 HAc-NaAc buffer. The results show that monodispersed silica spheres with a high BSA loading have great potential for applications in large-scale chiral separation processes.