Displacement chromatography process

A process of separating a preselected hemoglobin from a crude solution thereof which also contains contaminating proteinaceous substances, said process comprising:

• in a first chromatographic stage, feeding the crude solution to a chromatographic column and subjecting it to chromatography under either anionic exchange conditions under which components of the crude solution more acidic than said preselected hemoglobin have preferential binding affinity thereover, or to cationic exchange conditions under which components of the crude solution more basic than said preselected hemoglobin have preferential binding affinity thereover;
• continuing the feed of the crude solution in the first chromatographic stage until the column is substantially fully loaded with hemoglobin species and components of greater affinity;
• further continuing the feed of the crude solution in the first chromatographic stage to cause column overload and subsequent displacement of the hemoglobin species therefrom;
• in a second chromatographic stage, feeding the hemoglobin species-containing eluent from the first stage to a chromatographic column and subjecting it to chromatography under said anionic exchange conditions or cationic exchange conditions not selected for said first stage;
• continuing the feed of said eluent in the second chromatographic stage until the column is substantially fully loaded with hemoglobin species and components of greater affinity under said second stage conditions;
• further continuing the feed of said eluent in the second chromatographic stage to cause column overload and consequent displacement of the hemoglobin species therefrom.