We are trying to separate those two compounds by HPLC with chiral colunm. Anyone has suggestions and comments on colunm and other conditions that might be useful to try. Just briefly, molecular formula of UDP-GaINAc is same as UDP-GlcNAc except that the -OH group at C4 of the sugar is in "up" position. The full name of UDP-GlcNAc is UDP-N-acetyl-D-glucosamine UDP-2-acetamido-2-deoxy-D-glucose. Thanks for your help.