Methods are disclosed for separating hemoglobin from erythrocytes by contacting erythrocytes with a hypotonic buffer solution at a rate sufficient to render the release of hemoglobin from said erythrocytes without significant lysis. The hemoglobin is then separated from the erythrocytes. Methods are also disclosed for purifying hemoglobin solutions of DNA, endotoxins and phospholipids by contacting the hemoglobin solutions with an anion exchange medium.