Teicoplanin bonded sub-2 μm superficially porous particles for enantioseparation of native amino acids

Abstract

Superficially porous particles (SPPs) demonstrate superior efficiency than totally porous particles in chiral separations. In order to obtain high efficiency and fast separation, sub-2μm SPPs with high surface area are synthesized, and with teicoplanin bonded, such materials are successfully applied into the rapid enantioseparation of native amino acids. In brief, 1.27±0.06μm nonporous silica particles are prepared by a modified seeded growth method, followed by mesoporous shell fabrication via one-pot templated dissolution and redeposition strategy, and pore size expansion via acid-refluxing. The diameter of the formed SPPs is 1.49±0.04μm, with the shell thickness as 206nm. Nitrogen physisorption experiments show that the Brunauer–Emmett–Teller (BET) specific surface area is 213.6m2/g and pore size is 9nm. After teicoplanin derivatization with bonding capacity as 83.3μmol/g, the prepared chiral stationary phase is packed into a stainless steel tube with the geometry of 50mm×2.1mm i.d.. In less than 6.4min, six native amino acids (norleucine, alanine, valine, methionine, leucine, norvaline) are enantioseparated with resolution factors ranging from 1.9 to 5.0. Besides, the resolution for chiral separation is improved with ethanol-water instead of methanol-water as the mobile phase. Moreover, the low temperature gives higher resolution, but longer retention time and higher backpressure. Finally, the effect of flow rate on enantiomeric separation is studied and fast chiral separation within 1min is obtained with flow rate of 0.4mL/min. All these results show that the synthesized teicoplanin bonded sub-2μm SPPs have great potential to achieve the enantioseparation of native amino acids with high resolution and rapid speed.