Abstract: A device for extracting plasma from a fluid collection tube comprising: a tubular barrel having sidewall surrounding a lumen which extends between proximal and distal ends thereof, the tubular barrel forming a tip at a distal end; a barrel seal movingly seated within the lumen of the tubular barrel, the barrel seal closing and sealing the proximal end of the tubular barrel; a tube seal having a proximal end, a distal end, and a lumen extending therebetween, the proximal end having a frustoconical or chamfered face, the tube seal having an outer diameter sized to sealingly engage with an inner surface of the fluid collection tube, and an inner diameter sized to sealingly engage with an outer surface of the tip of the tubular barrel, the tube seal mounted on the tubular barrel such that the tip of the tubular barrel extends into the tube seal lumen.

Abstract: A separation container for extracting a portion of a sample for use or testing and method for preparing samples for downstream use or testing are provided. The separation container may include a body defining an internal chamber. The body may define an opening, and the body may be configured to receive the sample within the internal chamber. The separation container may further include a seal disposed across the opening, such that the seal may be configured to seal the opening of the body, and a plunger movably disposed at least partially inside the internal chamber. The plunger may be configured to be actuated to open the seal and express the portion of the sample.

Abstract: A separator separates a first from a second phase of a liquid in a tubular container. The separator has a float made of elastic material having a circumferential sealing edge and at least one ballast fastened to the underside of the float. The density of the ballast is greater than the density of the float and the density of the entire separator lies in a value range between the density of the first phase and the density of the second phase of the liquid. In order to securely prevent penetration of parts of the second phase of the liquid into the region above the separator within the tubular container, when the separator moves into the sealing position and is positioned there, the sealing edge of the float is formed at a predetermined distance greater than zero above the center of gravity of the entire separator.

Abstract: A device for extracting plasma from a fluid collection tube comprising: a tubular barrel having sidewall surrounding a lumen which extends between proximal and distal ends thereof, the tubular barrel forming a tip at a distal end; a barrel seal movingly seated within the lumen of the tubular barrel, the barrel seal closing and sealing the proximal end of the tubular barrel; a tube seal having a proximal end, a distal end, and a lumen extending therebetween, the proximal end having a frustoconical or chamfered face, the tube seal having an outer diameter sized to sealingly engage with an inner surface of the fluid collection tube, and an inner diameter sized to sealingly engage with an outer surface of the tip of the tubular barrel, the tube seal mounted on the tubular barrel such that the tip of the tubular barrel extends into the tube seal lumen.

Abstract: This disclosure is directed to an apparatus, system and method for retrieving target material from a suspension. A system includes a processing vessel, a displacement fluid, and a tube. The tube includes a funnel, a cannula, and a cavity. The cannula allows for fluid communication between the funnel and the cavity, such that the processing vessel is inserted into the cavity, and the cannula extends into the processing vessel.

Abstract: A system for separating and transferring phases of a fluid through centrifugation including a centrifuge having a rotating axis, a platform that is rotatable around the rotating axis; and a device for separating and transferring the phases of the fluid. The device includes a separating container and a receiving container connected to the separating container through a connecting channel. A passive valve system is provided in the connecting channel. The device is mounted in the centrifuge platform such that in use at a first predefined range of centrifugal force a fluid provided within the separating container is separated into phases and at a second predefined range of centrifugal force the valve system opens, thereby transferring a phase of the fluid from the separating container to the receiving container.

Abstract: The invention relates to devices, methods and kits for separating biological materials, particularly populations of cells of different densities. The invention finds particular utility in the separation of blood into its different component parts or cellular populations. An insert for a centrifuge tube is disclosed that facilitates the effective separation of blood fractions by achieving a sharp and distinct interface between the density gradient medium and the blood sample. Methods and kits involving the use of the insert in separating cells are described.

Abstract: A blood filtering device has a filtration section with filter medium separating raw side and clean side. A first communication path connects raw side and a first variable blood reservoir volume; a second communication path connects raw side and a second variable blood reservoir volume coupled to a receptacle. When varying the first variable blood reservoir volume, blood contained therein flows through first communication path to raw side, plasma/serum passes through the filter medium from raw side to clean side, and residual blood flows from raw side through second communication path into the second variable blood reservoir volume. When varying the second variable blood reservoir volume, blood contained therein flows through second communication path to raw side, plasma/serum passes through the filter medium from raw side to clean side, and residual blood flows from raw side through first communication path into first variable blood reservoir volume.

Abstract: The present invention relates to a centrifuge container for a centrifuge rotor, with a base body comprising an opening, a vessel bottom and a longitudinal axis, the opening and the vessel bottom being situated opposite each other and the base body extending with its overall length between the opening and the vessel bottom, and the centrifuge container comprising, along the overall length of the base body, a first section extending from the opening and a second section extending to the vessel bottom, the centrifuge container comprising structure non-detachably connected to the container for reducing the flow resistance, the structure being provided exclusively in the region of the second section.

Abstract: The present invention is related to the field of tissue regeneration. It concerns more particularly new processes, tubes and devices for thrombin, platelet concentrate and wound healant preparations, alone or in combination with cell extracts, cell compositions and uses thereof.

Abstract: The invention relates to an elutriation chamber for an elutriator system for washing and/or isolating cells, in particular thrombocytes, which elutriation chamber comprises a feed line (1) for an aqueous medium containing the cells to be washed and/or to be isolated in suspended form, and a discharge line (2) for the washed and/or isolated cells, wherein the chamber (5) is rotationally symmetrical to the axis (a), characterized in that the ratio of the area of the section through the lumen of the chamber (5) perpendicular to the axis (a) at the widest point (5a-5b) to the area of the section (1a) through the feed line (1) is in the range of 1,000 to 250,000.

Abstract: Centrifuge vessels suitable for live cell processing include a bowl with a cap, and a tube inside the bowl extending between the cap and a lower portion of the bowl. The bottom of the bowl can have a closed annular ring surrounding a center mound. The vessels can be particularly suitable for processing low volumes of live cells for vaccines or other therapies.

Abstract: The invention relates to a system and method for obtaining a cellular fraction enriched with defined cells effective in promoting a defined cellular response from an in vivo cellular sample. The system is closable to the atmosphere, and includes a cell suspension collection tube containing gel and anticoagulant, adapted such that, when containing cell suspension and centrifuged after treatment the collection tube yields separation fractions, a first fraction comprising cellular fluid, a second fraction comprising gel layer, a third fraction comprising enriched cellular portion on top of the gel layer and a fourth fraction comprising a cell poor portion. The cell poor portion may be extracted and discarded prior to extracting the enriched cellular portion.

Abstract: A separation device that can include a separation tube or container that has a wall defining an internal volume into which a material can be placed is disclosed. The material can include a multi-component mixture or solution. A secondary tube or withdrawal cannula can be placed and/or moved within the tube to withdrawal a material form the tube.

Abstract: A separator for use in a container for a biological fluid is disclosed. The separator includes a separator body having a first region at least partially made of a first material having a first density, and a second region at least partially made of a second material having a second density different from the first density. The separator has an overall density intermediate the densities of a first phase and a second phase of the biological fluid. At least a portion of the separator is deformable between a first condition in which the biological fluid can pass between an inner surface of the container and the separator, and a second condition in which at least a portion of the separator prevents the biological fluid from passing between the inner surface of the container and the separator.

Abstract: Sterilizable separator tubes and methods of utilization of same are presented. Methods include providing a separator tube containing a separator substance that can be polymerized to a desired hardness following sterilization using radical generating radiation. The separator substance is formulated to have a density between that of the average densities of separable fractions derived from a sample fluid such as blood, and to be flowable. Upon centrifugation of a separator tube containing a fluid sample, the separator substance forms a barrier between the fractions. The barrier subsequently hardens to form a solid barrier when triggered by a suitable energy source.

Abstract: A device for separating and isolating components of a biological fluid comprising a container for containing the fluid to be processed, a tube cap assembly for dosing the container while providing filling and extraction communication therewith, a float assembly disposed within the container for funneling and controlling biological fluid flow into an inverted domed shaped isolation chamber within the float and controlling the biological fluid flow out of the isolation chamber for effecting an encapsulation or a sealed isolation of at least one component or fraction of the biological fluid flow within the isolation chamber during a centrifugation process. The device further comprising a flexible tube for connecting an extraction passageway disposed within the float assembly and an extraction valve of the tube cap assembly for allowing extraction of at least the one component or fraction encapsulated or isolated within the chamber.

Abstract: A floating separating element for use in centrifugal separation of components of a physiological fluid comprises a positioning part and a separating part, where the positioning part is designed to automatically assume a position in a supernatant and a separating part is positioned at a desired location with respect to the interface between the supernatant and heavier components. In preferred embodiments the physiological fluids are blood or bone marrow aspirate, and the heavier components comprise red blood cells. The positioning part comprises the majority of the mass of the separating element and is thin so that differences in the position of the separating element with respect to the interface are small compared to differences in the densities of the separated components, particularly the component comprising red blood cells. A method allows red blood cells to move the separating element during decanting to ensure complete decant of the supernatant.

Abstract: A mechanical separator for separating a fluid sample into first and second phases within a collection container is disclosed. The mechanical separator may have a separator body having a through-hole defined therein, with the through-hole adapted for allowing fluid to pass therethrough. The separator body includes a float, having a first density, and a ballast, having a second density greater than the first density. A portion of the float is connected to a portion of the ballast. Optionally, the float may include a first extended tab adjacent a first opening of the through-hole and a second extended tab adjacent the second opening of the through-hole. In certain configurations, the separator body also includes an extended tab band disposed about an outer surface of the float. The separator body may also include an engagement band circumferentially disposed about at least a portion of the separator body.

Abstract: Methods of producing collection tubes are presented. The methods include providing a separator substance that can rapidly polymerize in a short time to a desired hardness and disposing the separator substance within the lumen of the tube. The separator substance is formulated to have a density between an average density of a serum fraction of whole blood and a cell-containing fraction of whole blood, and to be flowable with whole blood. Upon centrifugation of a tube having blood, the separator substance forms a barrier between the whole blood fractions. The tube and barrier maintain stability of one or more analyte levels, including potassium and glucose, within 10% of their initial values before centrifugation for at least four days.

Abstract: Methods and devices for preparing a solid-fibrin web are provided. One method may include drawing blood from a patient, separating plasma from the blood, contacting the plasma with a calcium-coagulation activator and concurrently coagulating and axially centrifuging the plasma to form the solid-fibrin web. The solid-fibrin web may be suitable for regenerating body tissue in a living organism. Devices used in the methods may also be provided.

Abstract: A mechanical separator for separating a fluid sample into first and second phases within a collection container is disclosed. The mechanical separator may have a separator body having a through-hole defined therein, with the through-hole adapted for allowing fluid to pass therethrough. The separator body includes a float, having a first density, and a ballast, having a second density greater than the first density. A portion of the float is connected to a portion of the ballast. Optionally, the float may include a first extended tab adjacent a first opening of the through-hole and a second extended tab adjacent the second opening of the through-hole. In certain configurations, the separator body also includes an extended tab band disposed about an outer surface of the float. The separator body may also include an engagement band circumferentially disposed about at least a portion of the separator body.

Abstract: A system and method for preparing and collecting samples for analyte testing. The system can include a sample preparation system and a sample collection system coupled to the sample preparation system. The sample preparation system can include at least one of a deformable self-supporting receptacle comprising a reservoir and a freestanding receptacle comprising a reservoir. The reservoir can be adapted to contain a liquid composition. The sample collection system can be positioned in fluid communication with a reservoir of the sample preparation system, and can be adapted to capture an analyte of interest. The method can include providing a fluid path defined at least partially by the sample preparation system and the sample collection system, positioning the liquid composition in a reservoir of the sample preparation system, and moving at least a portion of the liquid composition in the fluid path to the sample collection system.

Abstract: Disclosed is a composition for the separation of a serum or plasma, which comprises a cyclopentadiene oligomer, can be used for separating a serum or plasma by utilizing the difference in specific gravity among blood components, and enables to provide a serum or plasma having no oily component floating therein after centrifugal separation. The composition comprises a trimellitic acid ester and/or a pyromellitate ester and a cyclopentadiene oligomer. Alternatively, the composition comprises an aromatic esterified compound and a cyclopentadiene oligomer as the main ingredients and additionally comprises an inorganic micropowder and an organic gelling agent as thixotropy-imparting agents, wherein the organic gelling agent is contained in an amount of less than 0.06 parts by weight relative to 100 parts by weight of the cyclopentadiene oligomer.

Abstract: A collection device and a method for collecting a biological sample, particularly whole blood, includes a separating member to separate the whole blood into its components, and at least reagent positioned to selectively interact with a component of the separated sample. The reagent is able to selectively interact with the plasma/serum, and is prevented from contacting or interacting with the whole blood.

Abstract: The invention provides a serum or plasma separating composition which can compensate for the lack of initial thixotropy even at a reduced inorganic powder concentration and in which crevices or the like are less likely to be created in a partition wall formed of the separating composition after being centrifuged. The serum or plasma separating composition contains a liquid resin component having a partition wall-forming capability, a hydrophilic inorganic powder, a hydrophobic inorganic powder, and an organic compound serving as a thixotropy enhancer, wherein the organic compound is a polyalkylene glycol and/or a derivative thereof and is made of at least one type of polymer.

Abstract: A separator system operable to use centrifugation to fractionate a multiple component material, such as a suspension including blood, comprises a buoy. The buoy can be carried in a separation container and has a tuned density that is configured to reach an equilibrium position in the multiple component material. A guide surface is carried on a buoy upper surface and is inclined to an accumulation position near a buoy perimeter. The buoy suspension fractionation system can be used in a method of isolating a fraction from a suspension, and in a method for re-suspending particulates for withdrawal.

Abstract: A separation system for separating a multiple component material into at least two fractions. The separation system includes a separation device having a first end, a second end opposite to the first end, and a sidewall that extends between the first end and the second end to define a separation chamber having an interior volume. The system also includes a valve moveable between an open position and a closed position, the valve is mounted at a fixed location within the separation chamber at a position that is closer to the second end than to the first end and is spaced apart from the second end, the valve is operable to isolate a first fraction of the multiple component material having a first density on a first side of the valve from a second fraction having a second density on a second side of the valve that is opposite to the first side.

Abstract: Methods of producing collection tubes are presented. The methods include providing a separator substance that can rapidly polymerize in a short time to a desired hardness and disposing the separator substance within the lumen of the tube. The separator substance is formulated to have a density between an average density of a serum fraction of whole blood and a cell-containing fraction of whole blood, and to be flowable with whole blood. Upon centrifugation of a tube having blood, the separator substance forms a barrier between the whole blood fractions. The barrier rapidly hardens forming a solid barrier when triggered by a suitable energy source.

Abstract: A centrifugal assembly is provided that can be used in common laboratory fixed angle or swinging bucket centrifuges for the separation of material, such as parasitic ova, based on particle density. The centrifugal assembly allows the fluid level to be gently adjusted to form a meniscus without disruption of the buoyant matter, such as ova. The centrifugal assembly also enables a user to easily and hygienically collect and transfer a measured amount of a sample, such as fecal material, and to break apart and mix the sample with a floatation fluid contained in a centrifuge tube.

Abstract: A device for separating and isolating components of a biological fluid comprising a container for containing the fluid to be processed, a tube cap assembly for closing the container while providing filling and extraction communication therewith, a float assembly disposed within the container for funneling and controlling biological fluid flow into an inverted domed shaped isolation chamber within the float and controlling the biological fluid flow out of the isolation chamber for effecting an encapsulation or a sealed isolation of at least one component or fraction of the biological fluid flow within the isolation chamber during a centrifugation process. The device further comprising a flexible tube for connecting an extraction passageway disposed within the float assembly and an extraction valve of the tube cap assembly for allowing extraction of at least the one component or fraction encapsulated or isolated within the chamber.

Abstract: A device for separating and isolating components of a biological fluid comprising a container for containing the fluid to be processed, a tube cap assembly for closing the container while providing filling and extraction communication therewith, a float assembly disposed within the container for funneling and controlling biological fluid flow into an inverted domed shaped isolation chamber within the float and controlling the biological fluid flow out of the isolation chamber for effecting an encapsulation or a sealed isolation of at least one component or fraction of the biological fluid flow within the isolation chamber during a centrifugation process. The device further comprising a flexible tube for connecting an extraction passageway disposed within the float assembly and an extraction valve of the tube cap assembly for allowing extraction of at least the one component or fraction encapsulated or isolated within the chamber.

Abstract: The present invention is drawn to a method of measuring glycated hemoglobin, which can comprise steps of establishing multiple age-specific groups of red blood cells, and measuring HbA1c levels of at least one of said groups. In another embodiment, a system for measuring glycated hemoglobin can comprise a separating device configured to separate red blood cells into multiple age-specific groups, and a measuring device configured to measure HbA1c levels of at least one of said groups.

Abstract: A mechanical separator for separating a fluid sample into first and second phases is disclosed. The mechanical separator includes a float having a passageway extending between first and second ends thereof with a pierceable head enclosing the first end of the float, a ballast longitudinally moveable with respect to the float, and a bellows extending between a portion of the float and a portion of the ballast. The bellows is adapted for deformation upon longitudinal movement of the float and the ballast, with the bellows isolated from the pierceable head. The float has a first density and the ballast has a second density greater than the first density. The bellows is structured for sealing engagement with a cylindrical wall of a tube, and the pierceable head is structured for application of a puncture tip therethrough. The separation device is suitable for use with a standard medical collection tube.

Abstract: A blood specimen processor by means of which blood specimens are collected into a collection tube containing an anticoagulant and a molded buoy of predetermined density between 1.045 and 1.084 with an embedded water swellable o-ring that expands to form a robust seal in a leucocyte density gradient between the buoy's outer surface and tube's inner surface. The buoy is made of a first resin and a second resin, the first resin having a lower density than the second resin, the first resin and the second resin being present in such amounts and relative proportions so that the body has an overall density between 1.045 and 1.084 and preferably, a center of gravity below a geometric center of the body. When the blood specimen contained in the processor is centrifuged, the buoy is thrust through the separating blood and the developing interface of erythrocytes, leucocytes, and plasma.

Abstract: Some embodiments include a valve positioned within a test tube to maintain a separation between components of liquid with different densities after centrifugation. The valve preferably includes a cylindrically shaped housing with a conical plug configured to nest within the housing. The plug is not in contact with the housing during centrifugation, but comes into position post-centrifugation.

Abstract: A floating separating element for use in centrifugal separation of components of a physiological fluid comprises a positioning part and a separating part, where the positioning part is designed to automatically assume a position in a supernatant and a separating part is positioned at a desired location with respect to the interface between the supernatant and heavier components. In preferred embodiments the physiological fluids are blood or bone marrow aspirate, and the heavier components comprise red blood cells. The positioning part comprises the majority of the mass of the separating element and is thin so that differences in the position of the separating element with respect to the interface are small compared to differences in the densities of the separated compoments, particularly the component comprising red blood cells. A method allows red blood cells to move the separating element during decanting to ensure complete decant of the supernatant.

Abstract: The present invention provides a centrifugal separation-use device capable of maintaining a centrifugal separation-use container in a clean state easily at low cost even when centrifugal separation treatment is carried out using a centrifugal separator in an unclean field. A centrifugal separation-use device 1 for collecting a target component by subjecting a solution containing multiple components to centrifugal separation treatment comprises an inner container 10 having a cylindrical section 12 for accommodating the solution and a plug 14 for hermetically sealing the cylindrical section and configured so as to accommodate the solution in a hermetically sealed state, and an outer container 20 having a support section 22 for removably accommodating the cylindrical section and a delivery section 24 for exposing part of the inner container so that the inner container can be removed, and configured so as to accommodate the inner container in a hermetically sealed state.

Abstract: Disclosed is a system to separate, enrich, and/or purify a cellular population from a biological tissue, such as a tissue sample. For example, an adipose tissue sample can be acquired and disrupted. The disrupted tissue sample can then be separated and purified. The separated components can include multipotent, pluripotent, or other cell populations.

Abstract: Methods of producing collection tubes are presented. The methods include providing a separator substance that can rapidly polymerize in a short time to a desired hardness and disposing the separator substance within the lumen of the tube. The separator substance is formulated to have a density between an average density of a serum fraction of whole blood and a cell-containing fraction of whole blood, and to be flowable with whole blood. Upon centrifugation of a tube having blood, the separator substance forms a barrier between the whole blood fractions. The barrier rapidly hardens forming a solid barrier when triggered by a suitable energy source.

Abstract: A floating separating element for use in centrifugal separation of components of a physiological fluid comprises a positioning part and a separating part, where the positioning part is designed to automatically assume a position in a supernatant and a separating part is positioned at a desired location with respect to the interface between the supernatant and heavier components. In preferred embodiments the physiological fluids are blood or bone marrow aspirate, and the heavier components comprise red blood cells. The positioning part comprises the majority of the mass of the separating element and is thin so that differences in the position of the separating element with respect to the interface are small compared to differences in the densities of the separated components, particularly the component comprising red blood cells. A method allows red blood cells to move the separating element during decanting to ensure complete decant of the supernatant.

Abstract: Methods for using a centrifuge are presented. A vessel containing a sample and a separator substance is placed within a centrifuge. Upon sufficient centrifugation, the sample separates into two or more fractions separated by the separator substance. The centrifuge exposes the separator substance to a sufficient energy to polymerize the separator substance to produce a hardened barrier between the fractions.

Abstract: Disclosed herein are apparatus and methods for isolating a fraction of interest from a physiological fluid sample. A sample holder for isolating a fraction of interest from a physiological fluid sample includes a flexible compartment and a rigid exoskeleton that supports the flexible compartment. The flexible compartment may have at least one reservoir with a height to volume ratio of about 0.1 cm/mL to about 5 cm/mL. An automated device for extracting a fraction of interest from the sample includes a sample holder with a flexible compartment supported by a rigid exoskeleton, a support for the sample holder connected to one or more fluid extraction devices, and a motor for moving the extraction device relative to the sample holder. The automated device may include an optical sensor and may include a clamp for clamping the flexible compartment.

Abstract: A method and apparatus can separate and concentrate a selected component from a multi-component material. The multi-component material may include a whole sample such as adipose tissue, whole blood, or the like. The apparatus generally includes a moveable piston positioned within a separation container and a withdrawal tube that is operable to interact with a distal end of the collection container past the piston. Material can be withdrawn through the withdrawal tube.

Abstract: A device for separating and isolating components of a biological fluid comprising a container for containing the fluid to be processed, a tube cap assembly for closing the container while providing filling and extraction communication therewith, a float assembly disposed within the container for funneling and controlling biological fluid flow into an inverted domed shaped isolation chamber within the float and controlling the biological fluid flow out of the isolation chamber for effecting an encapsulation or a sealed isolation of at least one component or fraction of the biological fluid flow within the isolation chamber during a centrifugation process. The device further comprising a flexible tube for connecting an extraction passageway disposed within the float assembly and an extraction valve of the tube cap assembly for allowing extraction of at least the one component or fraction encapsulated or isolated within the chamber.

Abstract: An apparatus is disclosed that allows for separating and collecting a fraction of a sample. The apparatus, when used with a centrifuge, allows for the creation of at least three fractions in the apparatus. It also provides for a new method of extracting the buffy coat phase from a whole blood sample. A buoy system that may include a first buoy portion and a second buoy member operably interconnected may be used to form at least three fractions from a sample during a substantially single centrifugation process. Therefore, the separation of various fractions may be substantially quick and efficient.

Abstract: A method and apparatus for separating and concentrating a selected component from a multi-component material. The multi-component material may include a whole sample such as adipose tissue, whole blood, or the like. The apparatus generally includes a moveable piston positioned within a separation container and a withdrawal tube that is operable to interact with a distal end of the collection container past the piston. Material can be withdrawn through the withdrawal tube.

Abstract: A method and apparatus can separate and concentrate a selected component from a multi-component material. The multi-component material may include a whole sample such as adipose tissue, whole blood, or the like. The apparatus generally includes a moveable piston positioned within a separation container and a withdrawal tube that is operable to interact with a distal end of the collection container past the piston. Material can be withdrawn through the withdrawal tube.

Abstract: An apparatus that allows for separating and collecting a fraction of a sample. The apparatus, when used with a centrifuge, allows for the creation of at least three fractions in the apparatus. It also provides for a new method of extracting the buffy coat phase from a whole blood sample. A buoy system that may include a first buoy portion and a second buoy member operably interconnected may be used to form at least three fractions from a sample during a substantially single centrifugation process. Therefore, the separation of various fractions may be substantially quick and efficient.

Abstract: Methods of producing collection tubes are presented. The methods include providing a separator substance that can rapidly polymerize in a short time to a desired hardness and disposing the separator substance within the lumen of the tube. The separator substance is formulated to have a density between an average density of a serum fraction of whole blood and a cell-containing fraction of whole blood, and to be flowable with whole blood. Upon centrifugation of a tube having blood, the separator substance forms a barrier between the whole blood fractions. The tube and barrier maintain stability of one or more analyte levels, including potassium and glucose, within 10% of their initial values before centrifugation for at least four days.