The first intermediate of the glycosylated hemoglobin is a labile aldimine compound (Schiff' Base), the amount of which is dependent on the concentration of hemoglobin andglucose. Consequently the formation of the stable ketoamine compound is mainly influenced by the level of the intermediate aldimine.From the comparison of the molar ratios it becomes evident that there is an excess of amino groups over the free aldehyde groups of the glucose. The amino group must be in its basic form (nucleophilic reagent) to react with the aldehyde group of the glucose. Therefore, the reactivity of the different amino groups depends on their individual pK. The Chromatographie and electrophoretic methods cannot differentiate between the aldimine and the ketoamine form of the adduct. Therefore, the aldimine should be eliminated before the determination of the glycosylated hemoglobin. This can be performed by repeated washing of the erythrocytes, by dialysis, by pH-shift or by chemical elimination. The chemical elimination of the Schiff base is performed by "transschiffization"-reaction with semicarbazide. The electrophoretic and Chromatographie behaviour of the stable ketoamine form ist not influenced by the eliminator reagent.

Zusammenfassung: Das Mikrosäuleverfahren ist ein in der methodischen Durchführung einfaches und in der Reproduzierbarkeit der Ergebnisse gutes Analysenverfahren. Es hat sich in Diagnose und auch in Therapiekontrolle des Diabetes bewährt. Die interne und externe Qualitätskontrolle weisen dieses Verfahren als ein-gut geeignetes Analysenprinzip aus. Eine Aufschlüsselung der Glykohämoglobine in die Fraktionen a, b und c erscheint primär nicht erforderlich, zudem treten analytische Schwierigkeiten auf. Die weitere Entwicklung muß abgewartet werden. Für die Zukunft sind in erster Linie stabile Standards zu fordern, mit denen alle analytischen Verfahren arbeiten und reproduzierbare Ergebnisse liefern. Mit Hilfe dieser stabilen Standards und unter Befolgung der Richtlinien der internen und externen Qualitätskontrolle kann die Analysenqualität verbessert werden. Schlüsselwörter: Probenvorbereitung -Mikrosäuleverfahren, Störmöglichkeiten -Methodenvergleich -Therapiekontrolle -interne und externe Qualitätskontrolle Summary:The microcolumn chromatography has been proved äs a simple and reproducible method to quantify the glycosylated hemoglobins. Therefore f the microcolumn method has been succesfully use'd in diagnosis and therapy control ofdiabetic patients. Actually a simple analytical method to determine the C-component of the glycohemoglobins is not available. The accuracy and the precision of the analytical methods can be only determined and improved if stable Standards with assigned values are available for the infernal and external quality control. The results of the comparison of the different analytical methods and the results of the external quality control confirm the microcolumn chromatography äs a useful method for the metabolic control of diabetic patients. Further resolution of the glycohemoglobins into the fractions a, b and c seems not to be necessary for the correct metabolic control of diabetic patients.