Liquid purification or separation – Filter – Vacuumized filtrate receiver
Patent
1996-08-09
1998-08-11
Lithgow, Thomas M.
Liquid purification or separation
Filter
Vacuumized filtrate receiver
21032175, 21032184, 210446, 210455, 210482, 210483, 264219, 264DIG48, 216 41, 216 48, 216 94, 216100, 216101, B01D 2901, B01D 6308, B29C 3342
Patent
active
057923540
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to filter wells which are useful for the separation of a solid phase from a liquid as well as to a method for their production.
1. Field of the Invention
Separation of solid phase from a solution is an ordinary action in the biotechnical laboratory and is mainly carried out either by centrifugation or by collecting the solid phase on a filter. As examples can be mentioned preparation of nucleic acids from bacteria, bacteriophages, DNA-synthesis, PCR-products etc. Such a filtration is usually carried out in so called filter wells or filter tubes, i.e. a small tube or the like, open at both ends and containing a filter through which the liquid phase is forced by applying a vacuum on the underside of the filter or a pressure on its upper side.
2. Description of the Related Art
A device for carrying out biochemical reactions in micro-titre plates where a solution is forced through filter wells by means of gas pressure is disclosed in our U.S. Pat. No. 5,273,718. In comparison with application of a vacuum, the use of a positive pressure on the upper side of the filter has, among other things, the advantage that both the solid phase and the liquid phase can be collected in a simple manner. It is further possible to use a greater pressure difference (i.e. greater than 1 bar) between the underside and the upper side of the filter.
Depending on the mechanical properties of the filter it may be necessary, especially at greater pressure differences, that the filter rests on the surface of a support fitted to the wall of the tube. As in the case of chromatography columns this filter support can be a bottom portion having a central outlet opening towards which a number of radial channels made in the support surface extend, e.g. in a star or spoke-like manner, for example as disclosed in GB-A-1.102.497 (which, however, relates to a water conduit filter).
A channel pattern of this kind shall, on one hand, have a sufficiently large area/volume to give an acceptable volume flow through the filter, but, on the other hand, it shall have as small volume as possible, since it is often a case of filtering and collecting very small volumes of liquid. The filter usually has such a porosity that it is air-proof, when the liquid has passed, and the liquid volume remaining on the underside of the filter can thus not be forced out of the filter well by gas pressure.
The capacity of the filter is also influenced by the effective filter area, i.e. the area of the filter which is not in contact with the support surface, which means that the support surface should be minimized.
The design of the channel pattern in the support surface will thus necessarily be based on a compromise between the above mentioned desires. The filter well constructions which have been available up to now have, however, not been entirely satisfactory, neither with regard to residual liquid volume nor with regard to an efficient utilization of the filter area.
At the production of these known constructions (generally by injection moulding) the recess pattern in the steel surface in question of the forming tool, which corresponds to the pattern of the desired support surfaces, has usually been made by means of so-called spark machining with a carbon electrode. Among other things this has meant that it has not been possible to make more narrow recesses in the tool than about 0.4 mm and thus not more narrow support ridges between adjacent flow channels in the bottom of the filter well. An example of a filter which has a support surface provided with a channel pattern having such ridge dimensions, but where these are fully satisfactory for the intended uses of the filter is described in GB-A-2.149.315.
SUMMARY OF THE INVENTION
According to the present invention it has been found that a more efficient filter support surface with regard to residual liquid can be obtained if the flow channel pattern is designed more densely and with finer and more shallow channels and ridges, or ribs, in between than for the known support surface constru
REFERENCES:
patent: 3967620 (1976-07-01), Noiles
patent: 4640777 (1987-02-01), Lemonnier
patent: 5269917 (1993-12-01), Stankowski
patent: 5273718 (1993-12-01), Skold et al.
patent: 5443723 (1995-08-01), Stankowski
patent: 5454951 (1995-10-01), Hoopman
Lithgow Thomas M.
Pharmacia Biotech AB
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