Purification of hemoglobin (Hb) solutions suggested as oxygen carriers is an imperative necessity. All processes currently used clear out the solutions of almost the totality of impurities that are able to negatively influence the transfusional efficiency of Hb. We have studied the stability (metHb measurement) of Hb purified by DEAE dextran chromatography (Spherodex, 10 mM phosphate buffer, pH 7.20) which eliminates lipopolysaccharides, enzymes and non heminic-proteins...without denaturing Hb. In spite of the improvements due to this purification method on the transfusional efficiency of non modified Hb solutions, the lack of enzymes involved in the protection of Hb against autooxidation (superoxide dismutase, peroxidase, catalase...) makes it much more vulnerable to the reagents used during the following chemical processes : pyridoxylation, polymerization or macromolecule binding, thereby leading to an important oxidation to metHb. These observations led us to question the optimal position of purification in a process of modified Hb preparation. We have shown the importance of this chromatographic position in working on pyridoxylated Hb bound to monomethoxypolyoxyethylene Spherodex chomatography appears to be a very satisfactory purification method, provided it occurs only at the last step of the process. Many authors have not been attentive to this phenomenon which could be found with other Hb modifications. This therefore imposes to study the best place to incorporate a particular purification step into a hemoglobin preparatory procedure.
