Glycosylation is the most common posttranslational modification in proteins and the carbohydrates participate in many biological processes. The number and type of glycoforms for a certain glycoprotein may change as a consequence of pathological processes. In our work a method for the separation of transferrin sialoforms has been developed, that permits the diagnostic of Congenital Disorders of Glycosylation (CDG) using a polybrene-dextran sulphate coating and CE-ESI-TOF methodologies. In order to improve the sensitivity the use of solid-phase extraction coupled on-line to CE-ESI-MS is studied and the SPE-CE-ESI-MS developed methods are applied for the characterization of rHuEPO glycoforms. The achieved separation and the high mass-resolving power of flight (TOF) mass detection allows to establish the most probable rHuEPO glycoforms.