The present invention relates generally to vacuum filtration devices, and more particularly to a novel disposable manual vacuum filtration device for separating solid particulate from a liquid specimen and which finds particular application where a relatively modest degree of vacuum and evacuated volume are required for filtration.
It is a common practice in the testing and analysis of many types of solid materials to place a sample of the material into a liquid reagent after which the liquid reagent is filtered from the solid reactant leaving it available for diagnosis or further testing or washing with other reagents. Similarly, liquids such as various types of body fluids may have solid test reactants admixed therewith after which the solid reactants are extracted from the liquid by filtering to facilitate analysis of the reactants. Still further, liquids which in their natural state may have micro-organisms present are frequently analyzed by filtering the micro-organisms from a liquid sample for incubating and analysis.
One technique for filtering solid reactants or microorganisms from liquid reagents or carriers is to employ a vacuum filtration device having a filter element on which a liquid sample is placed in a manner enabling the liquid to be drawn through the filter by vacuum so that the solid constituents are retained on the filter element. See, for example, U.S. Pat. Nos. 2,005,406, 2,896,787, and 3,782,175 each of which employs a vacuum chamber adapted to support a filter element at its upper end and which is operative to filter a liquid sample through the filter element when the vacuum chamber is connected to a source of vacuum. Another device which utilized suction to draw the liquid portion of a specimen through a filter element and which facilitates both on-site filtering and incubation of microorganisms in liquid specimens is disclosed in U.S. Pat. No. 2,879,207.
The filtering devices exemplified by the aforementioned U.S. patents exhibit a number of drawbacks. For example, they require a separate vacuum source such as a vacuum pump or an evacuated bottle to effect vacuum filtering; they are relatively bulky and cumbersome to use; and they require rather complex manipulation to accomplish the desired vacuum filtration.
More recently, attempts have been made to provide apparatus for liquid filtering and sampling which are of relatively small size and are operable by manual manipulation to effect pressure differential filtering. See U.S. Pat. Nos. 3,832,141, 3,846,077, 3,955,423, and 4,644,807. These devices, while being adapted to separate stratified immiscible liquids, do not enable manual manipulation to effect vacuum filtration of liquid specimens so as to filter out solid reactants or particulate for diagnosis. Moreover, these devices require that relatively close tolerances be maintained in the manufacture of their various components, thus increasing their cost significantly.