WO1990015664A1

WO1990015664A1 - Method and device for the quantification of a volume of a sediment or of a volume of a fluid with bad flow properties

Info

Publication number: WO1990015664A1
Application number: PCT/NL1990/000083
Authority: WO
Inventors: Oscar Maria Johannes Driessen
Original assignee: Oscar Maria Johannes Driessen
Priority date: 1989-06-16
Filing date: 1990-06-14
Publication date: 1990-12-27
Also published as: JP2966520B2; EP0477259B1; DE69015358D1; US5256314A; ES2068391T3; ATE115891T1; NL8901530A; JPH04506116A; AU5923690A; EP0477259A1; DE69015358T2

Abstract

The invention describes a convenient method and device to measure off exact volumes of fluids with bad flow properties such as for instance sediments of suspensions, for subsequent analysis in a laboratory. By condensation, volume measurement and subsequent analysis of the particles in a suspension, it becames practicable to investigate quantitatively how much of a compound is associated with the particles in the suspension. Examples of particles in question are erythrocytes and silt or ground particles. Examples of compounds transported by erythrocytes are bodyconstituents such as steroids and fatty acids or drugs. Examples of compounds associated with silt or ground particles are heavy metals and organic compounds. In the invention the material (9, 10, 11) with bad flow properties is compressed into a space (7) for instance by centrifugation, whereafter this space (7) can be opened on a well defined place (12) in such a way that the excess part of the sediment (11) and of the suspension (10) is discharged through the opening (12) whereas the remaining part of the sediment (11) occupies an exact known space volume. The remaining fluid or sediment with the defined volume is conveniently available for further analysis.

Description

Method and device for the quantitation of a volume of a sediment or of a volume of a fluid with bad flow properties.

The present invention refers to the technique for measuring off of exact known volume quantities of materials that flow badly .and in particular of volume quantities suitable to be investigated for their composition on a laboratory scale. Measuring off of a volume of a material that flows properly is without difficulties. By using a pipette the desired quantitiy can be dosed simply. However the quantitation of a volume of materials who do not flow properly does give problems. A pipette is less suitable because the sucking of an exact standardized quantity of this material into a pipette is not simple.

An example of such a material with bad flow properties is a sediment of red blood cells obtained after centrifuging blood to which an anticoagulant is added. The centrifuged mass of cells has bad flow properties as only about 2 percent (v/v) of plasma has left between the cells. In case that an exact known volume of the red cell mass can be measured off, it is thereafter possible to carry out an exact measurement of compounds associated with that red cell mass. This is especially important for compounds badly or only restrictively (saturable protein binding) solvable in plasma and which by measuring of plasma only are unsatisfactorily determi¬ ned in blood. Among many possible examples we mention the hormone hydrocortisone, the free fatty acid with a short chain and also medicament dipropylaceticacid (valproate) and the drug phenytoin.

The aim of the invention hence is to give a method with which materials with bad flow properties can be quantitated simply and exactly. The invention refers to a procedure in which the material is centrifuged in a reservoir in such a way that the material is urged against the radial outer side of the reservoir wall and at a place inside that wall excess material can be discharged by an opening in such a way that a radially inner surface of material is formed adjacent to that opening in such a manner that between that extreme wall and this surface of material an exact determined volume of material remains. By centrifuging or by pressure the resistance of the badly flowing material against displacement is overcome; the excess material is flung or pressed outside through the opening whereas the desired volume remains. In this way materials with a relative high viscosity or otherwise bad flow properties can nevertheless be measured with respect to volume.

The method of the invention is also appropriate for the measurement of the more heavy materials in a suspension. Herewith it is provided that the material is separated from the suspension by centrifuging in such a way that, once separated, the material forms a sediment on a relative large radial distance and the rest of the suspension is present on a relatively short distance from the centrifuge axis, whereas in the area in which the sediment __&_ contained the reservoir is opened in such a manner that upon further centrifugation the material that is present in radial direction between that outlet and the centrifuge axis together with the rest of the suspension is discharged. Therefore, the excess part of the sediment together with the rest of the suspension is being urged outof the opening due to the influence of the centrifugal force, leaving a known volume of the sediment in the reservoir. It is important to note that in this procedure in which the heavy particles of the suspension are urged together, the contact with the lighter part,also in suspended form is not lost, and this counteracts a possible tendency to change the concentration of compounds associated with the heavy particles during the procedure.

As an alternative, after forming a sediment by centrifugation and upon opening the reservoir an overpressure may be applied in the reservoir such that the material located at the side of the radial more internal surface facing away from the outer wall of the reservoir, and the rest of the suspension will be discharged.

The invention further refers to a device suitable for execu¬ tion of this method. Devices for the centrifugation of materials, containing a reservoir with a radially outer border wall, to be placed in a centrifuge are known. The invention uses such a device, whereby the reservoir is provided with an opening that can be closed and which radially is placed, situated inwardly with respect to the border wall and yielding a known space volume limited at the one side by that border wall and at the other side by the plane of revolution determined by the opening and concentric with respect to the rotational axis. The reservoir may have the shape of a tube and can be secured in a holder provided with a recipient into which the opening of the reservoir emerges, which holder with reservoir are to be placed radially in a centrifuge rotor. The material to be flung out of the opening of the reservoir during centrifugation can be collected in the recipient of the holder. It is of importance that at the end of the procedure no rests of the suspension can be found in or outside the reservoir other than in the space formed by the border wall- and- the opening- because any rests for instance at the holder facing side of the reservoir near the opening will hamper the collection of the fixed volume of the sediment enclosed between the border wall and the opening. Also it is undesirable that a reservoir to be handled is at the outside contaminated with blood.

The opening in the reservoir can be closed in several ways. Preferably the holder has an abutment surface facing away from the recipient in the holder, into which a canal emerges connected to the recipient. The reservoir has a supporting surface locatable opposite to that abutment surface into which the opening of the reservoir emerges and between abutment surface of the holder and supporting surface of the reservoir a packing is provided as closing the opening of the reservoir.

In this context a fair embodiment can be obtained if holder and reservoir can cooperate by means of a screw connection in such a way that in the screwed down position the packing will close the opening whereas in partly screwed loose position a free flow of material exists between the opening of the reservoir and the canal of the holder. The procedure of measuring the sediment of a suspension starts by centrifuging the reservoir tightly screwed down in its holder. During this first centrifugation step the sediment will be collected in the radial exterior part of the reservoir up to and beyond the opening. Subsequently the opening is made free as mentioned and in a second centrifugation step the superfluous part ^• of the suspension and of the sediment is discharged. In a preferred embodiment of the invention the holder has, from the abutment surface onwards firstly a cylindrical cavity of a relatively small diameter and subsequently a contiguous cylindrical cavity with a relatively large diameter, onto which the canal to the recipient is connected whereby the reservoir parts externaly are cylindrical and the diameter of the first reservoir part is smaller than the one of the cavity with relatively small diameter of the holder.

When the device is radially placed on a plane centrifuge rotor and hence not in a swing out rotor, part of the material to be investigated might flow out of the reservoir before the centrifuge starts spinning. To counteract this a piston may be placed on top of the material present in the reservoir. In this way a loss of material will be prevented. Preferably the device will be used to measure a certain volume of particles from a suspension,such as red blood corpuscles in blood. According to the invention the procedure starts centrifu¬ ging (about 10000 g) with the reservoir and holder tightly screwed together in order to separate the heavy particles of the suspension and to press the erythrocytes maximally together, that subsequently the reservoir is partly screwed loose from the holder and than in a second centrifugation step the superfluous sediment is removed through the opening and the canal. Between the first and second centrifugation step a plasma sample can be taken. Because the ope- ning in the reservoir has to be tightly closed during the first centrifugation step a vacuum may be maintained in the total device of reservoir and holder. This vacuum can be desirable in the case of bloodsampling (vacutainer).

The measurement of material in a suspension can be succes- fully undertaken with the device here described in case the specific weight of that material is higher than of the rest of the suspension. In case the material has a specific weight similar to or lower than the rest of the suspension, than other methods must be applied to concentrate that part of the suspension in the radial outer part of the reservoir before quantitative investigations on the concentrated particles with known volume can take place.

According to a variant of the invention a magnetic material in a suspension independent of the specific weight of the material can be measured by carrying out the device in such a way that outside the reservoir fitted into its holder an apparatus is located for generating a radial magnetic field in such a manner that the material by the force of the magnetic field is pressed to the outer border wall of the reservoir.

The invention will be explained further with reference to a tested embodiment:

Figure 1 shows a birds-eye view in perspective of a centrifuge with a plain rotor, provided with the device according to the invention.

Figure 2 shows a cross-section of the device invented with the opening in the reservoir locked.

Figure 3 shows a cross-section of the device invented with the opening in the "reservoir free.

The centrifuge as depicted in figure 1 is known and contains a plain rotor 1_^ in which at least two devices as invented can be placed diametrically opposite each other. The rotor 1_^ revolves in such a way that the material contained in the devices 2 is pressed radially to the exterior.

As depicted in figure 2 every device 2 consists of a holder 3_ -- & -■ reservoir 4. Using the screw-threads J> end 6 the reservoir 4 is fixed into the holder 2.- Reservoir 4 is a cylindric body with a first reservoir part with a relatively small diameter 7_ and a second larger reservoir part 8 in which the material to be investigated 2. is disposed. The material 2. is for instance a sludge with bad flow properties 10 in which more heavy particles 11 can be discerned. As an example the sludge is blood in which the more heavy particles are erythrocytes. To collect an exact and known volume of erythrocytes the reservoir 4 is centrifuged with the aperture annex small side channel 12 closed by the o-ring 15 as depicted in figure 2. By the centrifugation at about 10000 g the erythrocytes 11 are pressed into the first reservoir part with the small diameter 7_ to the radial outer border wall of the reservoir ft« At the end of the first centrifugation step the reservoir part 7_ as well as the adjoining part of the reservoir 8 is plentifull with maximally compressed erythrocytes 11 together with § 2% v v of plasma between these red cells.

As can be seen in figure 2 and as mentioned the reservoir part has an aperture 12, emerging into the supporting surface 13. of the reservoir 4. This supporting surface 13. faces the abutment 5 surface 14 of the holder 2.- Between the supporting surface 13. and the abutment surface 14 .an o-ring packing 1^ is situated. In the case the .reservoir 4 is tightly screwed into the holder the o- ring packing 15 will close the aperture 12 of the reservoir and consequently the material 2. cannot flow away out of the reservoir

10 4. On top of the material 2. ^a iston 24 can be placed in case that the device must be placed horizontally on a plane centrifugal rotor. This piston prevents the outflow of material 2. from a too well filled reservoir part 8 before spinning of the centrifuge. A swing out rotor and/or the filling of the large part 8 of the

15 reservoir 4 with an apropriate volume of blood makes the piston 24 redundant.

In figure 3 the reservoir 4 is screwed somewhat out of the holder 2 ^and hence in the second centrifugation step the o-ring 15 does not close the aperture 12. Therefore components 10 and 11 of

20 material 2. can -'^or instance by centrifugal force be pressed into the room 16 formed by supporting surface 1 , abutment surface 14 and the edge 17_ protruding with respect to the abutment surface, in which the narrowed part 18 of part 8 of the reservoir 4 fits tightly. Preceding this second centrifugation step the supernatant

25 plasma is pipetted off for independent analysis. From room 16 components 10 and 31 flow into canal 10. and subsequently in the recipient 20 at the radial outer side of the holder 3_- The sediment located between the bottom 21 of the more narrow part 7_ ⁰~^* -^^e reservoir 4 and aperture 12 cannot escape, however the material

30 located above the side channel and aperture 12 will do. This material will be the superfluous mass of erythrocytes and resting plasma. The short second centrifugation step lasts till the material above the aperture is assembled in the recipient 20. Thereafter the first reservoir part 7_ contains an exact known

35 volume of particles and some included fluid because the volume between bottom 21 of reservoir part 7_ and the aperture of the overflow is fixed .and known and because the included fluid between maximally compressed erythrocytes is constant. For an erythrocyte sediment obtained with a centrifugal force of about 10000 g the intercellular fluid is 62% v v. After the collection of a sediment with a known volume this mass can be easily and quantitatively removed from the reservoir 4 by centrifuging only the reservoir upside down in a tapered test tube.

As is depicted in the figures 2 and 3 there is a venting channel 22 opening into the recipient 20 in the reservoir part 7_ of the reservoir 4. This channel starts on the into the recipient- room 20 protruding front surface 25. of the reservoir 4 and protracts through the part with the screw-thread of reservoir 4 and emerges subsequently radially more to the core-line above the screw-thread and at two sides of the part 2.. By this air venting channel 22 it is prevented that by screwing the reservoir 4 down into the holder 2. - • ^~-^r pressure builds up in the recipient-room 20 as a consequence of a sealing off by the joining screw-threads. Such an air pressure must always be avoided as the flow of material through aperture 12 and channel 1°< might be hampered.

At least, the recipient 20 can be formed by a receptacle 22 that can be fitted to or loosened from the holder 2 -^>°-' instance with screw-thread, facilitating cleaning of the device.

Claims

1. Method for the measurement of an exact determined volume of a flowable material according to which an overmeasure of material is centrifuged in a reservoir in such a way that the material is pressed to the radial outer wall of the reservoir and on a site radial within this wall the excess material can be di¬ scharged through an opening or aperture or window whereby a radial more internal surface of the material is formed adjacent to the aperture in such a way that between the outer wall and that surface of the material an exact determined volume of material remains.

2. Method according to claim 1, whereby a material in a suspension is separated by centrifugation from this suspension in such a way that once separated that material forms a sediment on a relatively large distance from the centrifugal axis whereas the rest of the suspension is situated on a relatively smaller distance from the centrifugal axis, whereby in the area of the sediment the reservoir is opened in such a manner that upon further centrifugation the material located radially between that aperture and the centrifuge axis and the rest of the suspension will be discharged.

3. Method according to claim 1, whereby a material in a suspension is separated by centrifugation from this suspension in such a way that once separated that material forms a sediment on a relatively large distance from the centrifugal axis whereas the rest of the suspension is situated on a relatively smaller distance from the centrifugal axis, whereby in the area of the sediment the reservoir is opened in such a manner that upon applying an overpressure in the reservoir the material located at the side of the radial more internal surface facing away from the outer wall of the reservoir, and the rest of the suspension will be discharged.

4. Device for carrying out the method according to claim 1,2 and 3. containing a reservoir to be centrifuged with a radial exterior situated border wall, characterised in that the reservoir radially inward in relation to the border wall has an aperture that can be closed and that the volume of the space is limited on the one hand by said border wall and on the other hand by the circumfe- rential surface which is determined by that opening and which is concentric with respect to the centrifugal axis.

5. Device according to claim 4, whereby the reservoir is tube shaped and locatable in a holder provided with a recipient into which the aperture of the reservoir emerges, which holder together with the reservoir extending radially is to be placed in a centrifuge rotor.

6. Device according to claim whereby the reservoir con- sists of a first part bordering his bottom with an exact determined volume, and a second part situated between the first part and the entry of the reservoir.

7. Device according to claim 6 whereby bordering the first part of the reservoir a lateral aperture exists in the second part.

8. Device according to one of the claims 5 up to and including 7 whereby the holder has an abutment surface facing away from the recipient into which a canal emerges that is connected to that recipient, the reservoir has a supporting surface to be placed opposite to the abutment surface of the holder into which the aperture emerges, and between abutment surface and supporting surface a packing is provided to close the aperture.

9- Device according to claim 8 whereby holder and reservoir can co-operate by a screw or other connection in such a way that in a tightly fitted position the packing will close the aperture whereas in a partially unscrewed or unfitted position a free flow connection exists between the aperture of the reservoir and the canal in the holder.

10. Device according to claim 8 or 9 whereby the holder has a circular edge protruding from the abutment surface and the reservoir has a circular circumference part at the supporting surface that fits tightly within that edge.

11. Device according to claim 9 or 10 whereby the holder beginning at the abutment surface firstly has a cylindrical cavity with a relatively small diameter and joining this cavity a cylindrical cavity with a relatively large diameter to which the canal is connected.

12. Device according to claim 11 whereby the_pacts_of. ths_ reservoir are cylindrical at the outside and the diameter of the first part of the reservoir is smaller that the one of the cavity with a relative small diameter of the holder.

13. Device according to one of the claims 9 to and inclu¬ ding 12 whereby the co-operating screw-threads are situated on the outside of the first part of the reservoir and on the inside of the cavity with a relatively small diameter of the holder.

14. Device according to claim 13 whereby an air venting channel is provided in the first part of the reservoir emerging at the beginning and at the end of the portion provided with εcrew- thread.

15. Device according to one of the claims 6 to and including 14 whereby in the second part of the reservoir a counter-piston can be placed, destined to close the suspension into the reservoir when the device has to be placed horizontally in a centrifuge rotor.

16. Device according to one of the claims 5 to and including 15 whereby the holder is equipped with a removable bottompart or recipient.

17. Device according to claim 4 for measuring magnetisable material in a suspension whereby exterior with respect to the reservoir an aparatus is placed generating a radial magnetic field in such a manner that material influenced by the magnetic field can be pressed to the outside wall of the reservoir.

18. Use of the device according to one of the claims up to and including 16 for carrying out the method according to claim 2 characterised in, that reservoir and holder are centrifuged for a first time tightly screwed together in order to separate the more heavy components of the suspension from the lighter ones or to press a liquid with bad flow properties into the radial exterior end of the reservoir and that subsequently the reservoir is partly unscrewed or unfitted and a second centrifugation is executed to discharge through the aperture of the reservoir and the channel of the holder the excess suspension material or the excess fluid with bad flow properties.

19. Use of the device according to one of the claims 9 up to and including 16 for carrying out the method according to claim 3. characterized in that reservoir and holder are centrifuged for a first time tightly screwed together in order to separate the more heavy components of the suspension from the lighter ones or to press a liquid with bad flow properties into the radial exterior end of the reservoir and that subsequently the reservoir is partly unscrewed or unfitted and an overpressure is applied to discharge through the aperture of the reservoir and the channel of the holder the excess suspension material or the excess fluid with bad flow properties.