Liquid purification or separation – Processes – Separating
Patent
1991-12-13
1993-10-26
Dawson, Robert A.
Liquid purification or separation
Processes
Separating
210361, 210515, 210516, 210518, 422 72, 422101, B01D 2126
Patent
active
052563146
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a device for measuring off of a volume of a flowable material, comprising a centrifugable reservoir provided with a bottom, side-walls and an entrance opposite the bottom. Measuring off of a volume of a material that flows easily is without difficulties. By using a pipette the desired quantitity can be dosed simply. However the quantitation of a volume of materials which do not flow easily does give problems. A pipette is less suitable because the sucking of an exact standardized quantity of this material into a pipette is not simple.
Also in the literature devices are described that can seperate fluids with good streaming properties in such ways semiquantitatively such as for instance plasma (patent document U.S. Pat. No. 3,905,528) or serum (patent document DE-U-8808138) from a sediment. However these devices are not constructed in order to measure off an exact known volume, let alone can these devices measure off exactly a volume of a fluid with poor streaming properties.
An example of such a material which does not flow easily is a sediment of red blood cells obtained after centrifuging blood to which an anticoagulant is added. The centrifuged mass of cells does not flow easily as only about 2 percent (v/v) of plasma remains between the cells. In case that an exact known volume of the red cell mass can be measured off, it is thereafter possible to carry out an exact measurement of compounds associated with that red cell mass. This is especially important for compounds that are little or only restrictively (saturable protein binding) solvable in plasma and which by measuring of plasma only are unsatisfactorily determined in blood. Among many possible examples we mention the hormone hydrocortisone, the free fatty acid with a short chain and also medicament dipropylaceticacid (valproate) and the drug phenytoin.
The quantitation of a volume of materials which do not flow easily does give problems. The use of a pipette is impossible because the sucking of an exact standardized quantity of such material into a pipette is unfeasable. Because a force considerably greater than gravity or vacuum pressure must be applied to propel a fluid with really poor streaming properties, devices constructed to measure off such fluids must contain a mechanism producing an exact and stable volume of the material in question, whereas, that volume is not to be influenced by the kind or degree of the applied force.
The aim of the invention hence is to give a device with which materials which do not flow easily can be quantitated simply and exactly. This acheived in that the device is provided with an occludable aperture situated between the bottom and the entrance, which aperture can be closed for collecting an overmeasure of the material in the reservoir pressed towards the bottom thereof during a first centrifuge run and which aperture can be opened for discharging the excess volume of the above collected material during a second centrifuge run such that an exact predetermined volume of the material is retained in the reservior between the aperture and the bottom.
The reservoir may be secured in a container provided with a receplacle into which the opening of the reservoir emerges, which container with reservoir are to be placed radially in a centrifuge rotor. The material to be flung out of the opening of the reservoir during centrifugation can be collected in the receptacle of the container. It is of importance that at the end of the procedure residue of the suspension can be found in or outside the reservior other than in the space formed by the border wall and the opening because any residue for instance at the container facing side of the reservior near the opening will hamper the collection of the fixed volume of the sediment enclosed between the border wall and the opening. Also it is undesirable that a reservoir to be handled is on the outside contaminated with blood.
The opening in the reservoir can be closed in several ways. Preferably the container has an abutment surface facing away
REFERENCES:
patent: 3905528 (1975-09-01), Maiocco
patent: 4052320 (1977-10-01), Jakubowicz
patent: 4933291 (1990-06-01), Daiss et al.
patent: 4935147 (1990-06-01), Ullman et al.
Dawson Robert A.
Reifsnyder David
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