Differences in cell density are exploited to separate granulocytes and erythrocytes from peripheral

blood mononuclear cells (PBMCs). The most common technique for separating PBMCs is to mix blood

with a compound which aggregates the erythrocytes, thereby increasing their sedimentation rate. The

active ingredients in the SepOBuffer™ are sodium diatrizoate and polysaccharide with osmolality

290 +15 mOsm/L and density of 1.077 +0.001 g/ml. The polysaccharide in SepOBuffer™ enhances

erythrocyte aggregation increasing erythrocyte sedimentation during centrifugation. PBMCs with lower

densities remain in the plasma SepOBuffer™ interface and can be collected from the upper part of the

tube when the erythrocytes have settled. The PBMCs from whole blood can be reliably and rapidly

isolated in pure form using SepOBuffer™.