Enantiomeric separation of amino acids and nonprotein amino acids using a particle-loaded monolithic column

A solution is prepared of 5 mu m silica particles modified with (S)-N-3,5-d initrobenzoyl-1-naphthylglycine (particle 1) or (S)-N-3,5-dinitrophenylamin ocarbonyl-valine (particle 2) suspended in liquid tetraethylorthosilicate, ethanol, and aqueous hydrochloric acid. This solution is injected under pre ssure into a 30 cm long, 75 mu m inner diameter capillary column and heated for 1 h at 120 degrees C after which the modified particles are embedded i n a monolithic column of sol gel. The packed column measures approximately 15 cm from the inlet to the window used to view the laser-induced fluoresce nce. Thirteen different amino acids and three nonprotein amino acids are de rivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazol e (NBD-F) before injection onto the column for capillary electrochromatogra phic separation. The enantiomeric separation of the monolithic column pack: ed with particle 1 results in a resolution ranging from 1.14 to 4.45, where as that packed with particle 2 results in a resolution ranging from 0.79 to 1.17. On the basis of resolution and amount of chiral packing material the enantiomeric separation obtained by capillary electrochromatography is jud ged to be superior to that obtained previously with high performance liquid chromatography (HPLC).