Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Patent
1996-04-30
1998-12-29
Alexander, Lyle A.
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
422 58, 422 61, G01N 3348
Patent
active
058536701
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a liquid transfer device particularly, but not exclusively, for liquid sequencing, timing and volume metering in chemical diagnostic assays in extra-laboratory situations.
BACKGROUND OF THE INVENTION
Various liquid transfer devices have been proposed and designed to avoid any need for complex procedures, so as to be suitable for use by relatively inexperienced persons. In some assays, it is necessary for there to be a timed sequence of reagent additions to an analyte, and devices have been previously proposed to deliver such reagents automatically and sequentially by the use of multiple capillary flow channels. Examples of capillary flow diagnostic devices are described, for example, in GB-A-2231150 and corresponding WO90/11519. Sequential delivery of reagents in such devices is achieved by forming the flow channels of different effective lengths so that the reagent which is in the flow channel of longer effective length is delivered later than the reagent in the flow channel of shorter effective length. However, this can lead to a relatively bulky device.
GB-A-2231150 also discloses various diagnostic devices which include an expanding foam which is intended to connect the flow channels together automatically after a predetermined time. However, it is not always easy to arrange the foam to expand reproducibly, either due to material properties, or interfacial connection or circuit configuration.
It has also been proposed by M. P. Allen et al, Clinical Chemistry 36 (1990), 1591 to provide a manually operable valve mechanism for shearing off a defined volume of sample into a liquid transfer device so as to ensure that a relatively accurate sample volume is used, thereby to reduce the possibility of error. However, the mechanism is manually operated and involves the use of precision moving parts which are relatively expensive to manufacture.
U.S. Pat. No. 5,240,862 discloses a device incorporating a red cell separation membrane in temporary contact with a sample collection membrane of known volumetric capacity. In use, whole blood is applied to the separation membrane which separates and applies serum to the collection membrane. The separation membrane containing red cells and excess plasma is manually removed from the collection membrane and discarded. The defined volume of the plasma contained in the collection membrane is then eluted out and analysed. Here again, a manual procedure is involved, and the separation membrane needs to be disposed of safely.
EP-A-0 418 765 describes a test device with flow control means constituted by a hydrophilic membrane in contact with a hydrophobic membrane. The hydrophilic membrane is accessible by way of a port such that an assay liquid may be applied to it. Once analyte present has bound to the hydrophilic membrane, further flow into the hydrophobic membrane can be initiated by applying a wetting agent. The device described offers no means to define the volume of the applied assay liquid, and if such liquid is applied in excess it will almost certainly tend to pass into the hydrophobic layer before the intended time, due to saturation of the pores. The procedure involved requires further intervention by a user who must apply the wetting agent at the correct time to the first channel as there is no way of accessing the hydrophobic membrane to apply any liquid to it.
SUMMARY OF THE INVENTION
WO-92/15863 teaches a test strip device comprising a wicking architecture within an impermeable housing. The device includes an application site accessible through a port, and applied sample, or a part thereof, can travel to an analysis site where a reagent causes a detectable change observable through a second port. The flow control means may include a glass fleece to separate red blood cells from whole blood. The application site is in flow connection with a peripheral sink, such that in operation excess sample is carried away from the operative site. Sample applied to the application site can immediately pass into the next layer before the sink has
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Alexander Lyle A.
British Technology Group Limited
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