Blood serum is one of the most interesting sources for important diagnostic markers. For a rapid test, especially when intended for point-of-care use, the classical methods of serum or plasma preparation are not practical. There is an increasing demand for whole-blood assays, which require separation of blood cells within the test device.
The separation of blood cells from plasma using a filter is a demanding task. The percentage of particulates (mainly erythrocytes, the contribution of leukocytes is negligible), the hematocrit or PCV (packed cell volume) is between 36 and 48% for females and between 40 and 53% for males. Peak values can be up to 70% (typically found in blood of Tour de France participants).This means that a droplet of blood from a finger stick does not contain much liquid. It is common for lateral flow immunoassays with whole-blood samples to add some reagent to the sample.This ensures that there is sufficient liquid volume to perform the assay. It is also advisable to add an anti-coagulant to this reagent to avoid clotting problems. In case of the presence of such an additive, the effective sample in the assay is plasma, not serum.
A blood separator for immunochromatographic assays is typically a cellulosic or glass fiber depth filter. In addition to efficiently removing blood cells, it must also yield a high recovery of plasma from the sample, must not cause red blood cells to break down (act hemolytic), and should not interact with the analyte in question.
Cytiva offers a family of blood separators to meet the increasing demands and strict requirements of the rapid diagnostics market:
- Separation in 30–120 seconds for rapid assays that save time.
- No appreciable red cell hemolysis for improved reproducibility of results.
- Consistency of materials provides reliable tests.
- Materials are suitable for use in a range of tests, giving flexibility in test optimization.
- Choice of separation times allows for test optimization.
- Separators are appropriate for a range of blood volumes to enhance the separation rate according to the volume of blood available.
Properties of Whatman™ blood separators
|Volume per sq cm
||Materials and uses
(μm @ 53 kPA)
|> 50 μl
||Vertical separator used as a single or multiple layers for separation.
|> 50 μl
||Untreated bound glass fiber.
||Untreated bound glass fiber suitable for whole blood or serum. Typically used for whole blood volumes between 30 µl and 100 µl.
||Untreated bound glass fiber suitable for whole blood or serum. Performs well with one or two drops of whole blood.
||Fusion 5 is a proprietary single-layer matrix membrane that can perform all of the functions of a lateral-flow strip. It can be used as sample wick as well as a blood separator with excellent separation efficiency.