FILTER AND DISPENSER VIAL AND USE THEREOF

Abstract: According to the invention, a piston fit filter and dispenser vial and method of using same is provided. The vial comprises a conventional filter (13), for example a piston fit serum filter closing the lower end of the vial and a closure having a pressure source fitting (25) closing off the upper end of the vial. The vial also includes a transfer tube having a first end inside the vial adjacent to the filter and a second end outside the vial. Filtrate, for example filtered blood serum, within the vial may be trans­ ferred in predetermined aliquots to one or more awaiting sample containers from the vial by applying a predetermined volume of air from a pressure source via the pressure source fitting whereby displaced serum is forced up the transfer tube and out of the vial.

Description: The invention relates to a piston-type filter and dispenser vial for dispensing measured aliquots of filtrate, said vial comprising: a hollow shaft including a side wall defining an interior, said hollow shaft having an upper end and a lower end; and a piston fit filter means located in and closing the lower end of the hollow shaft. The invention relates in particular to a filter and dispenser vial, which is especially suitable for filtering and dispensing measured aliquots of blood serum derived from a whole blood sample contained in a test tube. The invention further relates to the use of the vial for providing measured aliquots of a filtrate, and in particular of filtered blood serum. In the examination of blood samples, it is often necessary or desirable to examine blood serum after it has been separated from the suspended cellular material, and for this purpose it is customary to subject the specimen tubes, in which the blood samples are delivered to the laboratory, to centrifuging action to cause the settling of the cells to the bottom of the specimen tube. Since many laboratories process large numbers of blood samples every day, facility of handling specimens and the ease of drawing off and retaining serum specimens are important to successful and safe operation. The most widely employed method of separating the liquid phase component from the solid phase components of a blood mixture is centrifugation. When the serum is to be subjected to a diagnostic analysis with, for example, an automated electronic analyzer, it is important to employ a particulate-free specimen. Fibrin fibers are often the cause of analyzer malfunctions when they clog conduits or orifices in the analyzer. Filtration has been employed previously to remove solid particles such as minute fibers of fibrin not readily separated by centrifugation. Illustrative of the prior art blood component filtration devices are those described in U.S. Patent Nos. 3,481,477; 3,512,940; 3,693,804 and 3,832,141. In these serum separators, the sample is collected in a test tube and an elongated sampling tube is provided to fit within the test tube. In the lower end of the sampling tube is a piston head which makes a sliding seal with the side walls of the test tube. A filter is mounted in a passageway extending through the piston head to the interior of the sampling tube. As the sampling tube and piston head are pushed into the test tube, fluid will pass through the filter into the interior of the sampling tube leaving the residue in the bottom of the test tube. The sampling tube may subsequently be withdrawn, at which time the filtrate, which will be serum, will be withdrawn with the sampling tube. Filtered serum may be withdrawn from the sampling tube for an automated blood analysis by using, for example, an aspirating tube. See, for example, U.S. Patent No. 4,602,995. Alternatively, aliquots of serum may be transferred from the sampling tube into one or more sample containers by pipetting. For automated laboratory analysis of blood samples, it is desirable to separate each sample into multiple pre-measured aliquots of serum . In this manner, a plurality of separate blood samples may be aliquoted and then all sample aliquots requiring a particular laboratory analysis may be run through an automatic analyzer sequentially. There is a disadvantage associated with transferring serum from the sampling tube using pipetting or aspiration in that each of these techniques requires the introduction of a foreign object into the serum, sometimes more than once. For example, each introduction of a pipette or aspirating tube into serum sample involves the risk of contaminating the sample and also presents problems in maintaining the sterility of the pipette and/or aspirating tube. A main aim of the invention as claimed is therefore to provide an improved apparatus and improved method for collecting filtrate, particularly filtered serum, from a whole blood sample, and transferring predetermined aliquots of the filtrate to one or more separate containers, the improved apparatus/method making it possible to substantially reduce the risk of contamination of the sample. According to the invention the above aim is attained with a piston-type filter and dispenser vial for dispensing measured aliquots of filtrate upon the application of air pressure to said vial from an external air pressure source, said vial including: a. a hollow shaft including a side wall defining an interior, said hollow shaft having an upper end and a lower end; and b. piston-type filter means located in and closing the lower end of the hollow shaft; said vial being characterized in that it further comprises: c. a rigid transfer tube having a first end located within the interior of the hollow shaft and a second end located outside the hollow shaft; and d. closure means located in the upper end of the hollow shaft for closing the hollow shaft, said closure means including a fitting for connecting the interior of the hollow shaft with an external air pressure source. When the external air pressure source is engaged with the closure and air pressure is applied, filtrate within the vial is transferred therefrom via the transfer tube. The invention further relates to the use of a filter and dispenser vial according to the invention for providing measured aliquots of filtrate comprising steps of: a) inserting the vial into a test tube containing a solution to be filtered to thereby cause filtrate to flow up inside the hollow shaft; b) connecting an external pressure source to the fitting; and c) applying a predetermined volume of air to the inside of the hollow shaft from the external pressure source to transfer a predetermined aliquot of filtrate out of the hollow shaft through the transfer tube. The substantial advantage of the apparatus and method according to the invention is the elimination of the need to employ a separate pipetting operation, respectively separate pipetting means, for transferring portions of filtered serum from the interior of the vial to a number of containers. Thereby the apparatus and method according to the invention reduce the risk of contamination of the sample portions transferred, and enhance cleanliness and efficiency in laboratories. The preferred embodiment of the invention will now be described with reference to the following drawings, which are merely exemplary and are not meant to limit the scope of the invention in any respects. Figs. 1a-1c show a first embodiment of the piston fit filter/dispenser vial according to the invention in cross-section. Fig. 2 shows a second embodiment of the piston fit filter/dispenser vial according to the invention in cross-section. Figs. 1a-1c illustrate a first embodiment of the piston-type filter and dispenser vial according to the invention. Fig, 1a shows the vial 1 prior to insertion into a test tube 22 filled with a whole blood sample 23 to be filtered. Fig. 1b shows vial 1 after insertion into the test tube 22 but before aliquoting has occurred. Fig 1c shows vial 1 after insertion into test tube 22 and during application of air pressure via the pressure source 25 to aliquote a fraction of filtered serum 24 into a container 26. Referring to Fig. 1a, the vial comprises a hollow shaft 10 having a side wall 14 defining an interior 27. The hollow shaft 10 has a lower end 15 which is closed by filter assembly 28. The hollow shaft 10 also has an upper end 16 which is closed by closure 20. A transfer tube 17 is partially located within the hollow shaft 10. The transfer tube 17 has a first end 18 which opens into the interior 27 of the hollow shaft 10 preferably adjacent to the filter assembly 28 in the lower end 15. The transfer tube 17 has a second end 19 which is located outside the hollow shaft 10. As shown in Figs. 1a-1c, the transfer tube 17 extends out through the side wall 14 of the hollow shaft 10. The hollow shaft and the transfer tube 17 may be constructed integrally with the side wall 14 as shown or may be constructed as a separate element (not illustrated). The hollow shaft 10 and the transfer tube 17 are preferably manufactured from a transparent or semi-transparent material. The hollow shaft 10 may, for example, be constructed of glass or plastic which is preferably non-porous and inert to the intended filtrate. Suitable plastic materials for a serum filter application would include, polyacrylate, polyvinyl and polystyrene. The filter element 28 includes a filter 13. It will be understood that the invention does not reside in the particular configuration of the filter assembly 28 and any suitable filter assembly as is known in the art may be employed. The filter may be constructed of any suitable conventional material. However, in the case where the vial 1 is to be used for filtering blood serum, the filter material should preferably be inert to blood. The filter material should have pores which permit the passage of soluble blood components but prevent passage of insoluble blood components through the filter. More particularly, the pores should be sized to deny passage of solid and semi-solid particulate material having a spherical diameter of greater than 50 microns. Suitable filter materials would include porous plastic materials, more particularly porous polyethylene, porous polyurethane, porous tetrafluoroethylene and the like. Porous ceramic materials, sintered glass, glass wool, and the like may also be employed. The closure 20 includes a pressure source fitting 21, which is sized to receive the external pressure source 25 as shown in Fig. 1c. No particular material of construction is preferred for the closure 20. The closure 20 may be constructed integrally with the side wall 14 or may be constructed as a separate element which is held in the upper end 16 of the hollow shaft 10 by friction fit, for example. An alternative embodiment is illustrated in Fig. 2 wherein the transfer tube 17 extends out through closure 20 instead of through side wall 14. The operation of the vial according to the invention will now be described with reference to Figures 1a-1c. The following description of the operation of the vial according to the invention will, for illustrative purposes, relate to the filtration of serum from whole blood. However, it is understood that the vial according to the invention may be used to filter other substances besides whole blood. In a method according to the invention, a whole blood sample 23 is introduced into test tube 22. Following centrifugation to separate out the heavier components in the blood, the vial 1 is pushed down into the test tube 22. See Fig 1b. The pressure source fitting 21 permits air within the hollow shaft 10 to escape as serum 24 fills up inside. As shown in Fig. 1b, the vial after being pushed into test tube 22 filters out serum 24, which is then collected in the interior 27 of the hollow shaft 10. At this stage, and as shown in Fig. 1c, the external pressure source 25, for example a conventional automatic pipette, may be inserted into pressure source fitting 21. A predetermined volume of air may be forced into the interior 27 of the hollow shaft 10. As shown in Fig. 1c the air introduced into the hollow shaft 10 displaces a predetermined aliquot of filtered serum 24, which flows through transfer tube 17 out into container 26. This aliquoting operation may be repeated as many times as necessary to fill one or more additional containers 26 with predetermined aliquots of filtered serum 24 from the whole blood sample 23. The predetermined aliquots of filtered serum 24 within individual containers 26 are then ready to be transferred to automated analyzing equipment, for example. It will be recognized from the foregoing description that one advantage provided by the vial and method according to the invention is the elimination of the need to employ a separate pipetting operation to transfer filtered serum from the interior 27 of the vial 1 to awaiting containers 26. The vial 1 thus serves a dual function as not only a filter apparatus but also a dispensing apparatus. The external pressure source 25 will not need to come in contact with the filtered serum 24. This enhances cleanliness and efficiency in laboratories which may be handling large numbers of whole blood samples for analysis.

Claims: A piston-type filter and dispenser vial for dispensing measured aliquots of filtrate, said vial comprising: a. a hollow shaft (10) including a side wall defining an interior, said hollow shaft having an upper end (16) and a lower end (15); b. piston-type filter means (28) located in and closing the lower end (15) of the hollow shaft; said vial being characterized in that it further comprises: c. a rigid transfer tube (17) having a first end (18) located within the interior of the hollow shaft and a second end (19) located outside the hollow shaft (10); and d. closure means (20) located in the upper end (16) of the hollow shaft (10) for closing the hollow shaft, said closure means including a fitting (21) for connecting the interior of the hollow shaft (10) with an external air pressure source (25). A vial according to claim 1, wherein the first end (18) of the transfer tube (17) is located adjacent to said filter means (28) in the lower end (15) of the hollow shaft (10). A vial according to claim 1, wherein the transfer tube (17) extends out through the side wall (14) of the hollow shaft (10). A vial according to claim 3, wherein the first end (18) of the transfer tube (17) is located adjacent to said filter means (28) in the lower end (15) of the hollow shaft. A vial according to claim 1, wherein the transfer tube (17) extends out through the closure means (20). A vial according to claim 5, wherein the first end (18) of the transfer tube (17) is located adjacent to said filter means (28) in the lower end (15) of the hollow shaft (10). A vial according to one of claims 3, 4, 5 or 6, wherein the transfer tube (17) is integral with the side wall (14). A vial according to claim 1, wherein the fitting (21) is centrally located in the closure (20). Use of a filter and dispenser vial according to claim 1 for providing measured aliquots of filtrate comprising steps of: a) inserting the vial into a test tube (22) containing a solution to be filtered to thereby cause filtrate to flow up inside the hollow shaft (10); b) connecting an external pressure source (25) to the fitting (21); and c) applying a predetermined volume of air to the inside of the hollow shaft from the external pressure source (25) to transfer a predetermined aliquot of filtrate out of the hollow shaft (10) through the transfer tube (17). Use according to claim 9, wherein the external pressure source is a pipette. Use of a filter and dispenser vial according to claim 1 for providing measured aliquots of filtered serum comprising the steps of: a. inserting the vial (1) into a test tube (22) containing a coagulated centrifuged whole blood sample (23) to thereby cause filtered serum (24) to flow up inside the hollow shaft (10); b. connecting an external pressure source (25) to the fitting (21); and c. applying a predetermined volume of the air to the inside of the hollow shaft (10) from the external pressure source (25) to transfer a predetermined aliquot of filtered serum (24) out of the hollow shaft (10) through the transfer tube (17). Use according to claim 11, wherein the external pressure source is a pipette.

Inventors: FANSLER, DAVID VAUGHAN, KNESEL, ERNEST ARTHUR, JR., SHOEMAKER, DANIEL RAYMOND
Applicants: F. HOFFMANN-LA ROCHE AG
Application year: 1989
Main classification: G01N33
IPC codes: B01D33, A61B5, G01N33, B01L11, G01N35