Use o fa Novel Sub-2micron Silica Hydride Vancomycin Stationary Phase in Nano-LiquidChromatography. II. Separation of Derivatized Amino Acid Enantiomers

A novel vancomycin silica hydride stationary phase was synthesized and the particles of 1.8 ?m were packed into fused silica capillaries of 75 ?m internal diameter(I.D.).The chiral stationary phase (CSP) was tested for the separation of some derivatized aminoacid enantiomers by using nano-liquid chromatography (nano-LC).Some experimental parameters such as the type and the content of organic modifier,the pH,and the concentration of the buffer added to the mobile phase were modified and the effect on enantioselectivity,retention time,and enantioresolution factor was studied.The separation of selected dansylaminoacids(Dns-AAs),e.g.,Asp,Glu,Leu,and Phe in their enantiomers was initially achieved utilizing a mobile phase containing 85%(v/v)methanol(MeOH)and formate buffe rmeasuring the enantioresolution factor and enantioselectivity in the range 1.74-4.17 and 1.39-1.59,respectively.Better results were obtained employing a more polar organic solvent as acetonitrile(ACN)in th mobile phase.Optimum results(Rs 1.41-6.09and ? 1.28-2.36) were obtained using a mobile phase containing formate buffer pH 2.5/water/MeOH/ACN6:19:12.5:62.5(v/v/v/v)in isocratic elution mode at flow rate of 130nL/min.