Pipette and filter combination

A pipette having a liquid receiving hollow generally encompassed by deformable side walls, the pipette further has a tapered liquid outlet extending from one end of the hollow and a liquid inlet on the other end of the hollow within which is located a semi-permeable filter.

The present invention relates to pipettes. 
It is a disadvantage of known methods of separating the blood cells from 
plasma in centrifuged blood samples in that the plasma must be either 
tipped or pipetted off the cells into another receptacle. 
It is an object of the present invention to overcome or substantially 
ameliorate the above disadvantages. 
There is disclosed herein a pipette having a liquid receiving hollow 
generally encompassed by deformable side walls, a tapered liquid outlet 
extending from one end of said hollow, and a liquid inlet on the other end 
of said hollow and a filter located in said inlet.

In FIG. 1 there is schematically depicted a pipette 10 having a main body 
11 defining a calibrated hollow 12 which receives a liquid to be dispensed 
by the pipette 10. Extending from the body 11 is a tapered tip 13 which is 
adapted to accurately dispense the liquid contained in the hollow 12. The 
other end of the body 11 is provided with a neck 14 within which is 
received a filter 15. Additionally, the body 11 is provided with a 
flexible seal 16. The pipette 10 is to be made of plastics material so 
that the body 11 may be resiliently deformed to cause the liquid to exit 
through the tip 13. 
In practice the body 11 would be squeezed by the fingers of a user of the 
pipette 10 in order to cause the liquid to exit via the tip 13. 
Additionally the seal 16 should be flexible enough to resiliently 
sealingly engage against the internal surface of a test tube. 
Now also with reference to FIG. 2 there is schematically depicted a test 
tube 17 through which is received a sample of blood 18 which has been 
subjected to centrifugal force to cause the sample 18 to separate due to 
density differences into two liquids or phases 19 and 20. In the present 
instance the liquid or phase 20 would be a plasma and phase 19 is 
compacted blood cells. In order to extract the plasma 20 from within the 
test tube 17, the pipette 10 would be inserted in the test tube 17 so that 
the seal 16 would resiliently sealingly engage the internal surfaces of 
the test tube 17. 
The pipette 10 would be further moved so as to bear against the plasma 20 
and therefore force the plasma 20 to enter the body 11 of the pipette 10 
via the seal 15. Upon sufficient quantity of the plasma 20 being received 
within the body 11, the body 11 need only be resiliently deformed in order 
to dispense the plasma 20 via the tip 13. 
Referring now to FIGS. 3 to 5 wherein the pipette of FIGS. 1 and 2 is 
depicted as co-operating with the body of the syringe. As can be seen the 
pipette 30 sealingly co-operates with a syringe body 31 which terminates 
with a needle 32. The pipette 30 is basically the same construction as the 
pipette of FIGS. 1 and 2 in that the liquid inlet end 33 is provided with 
a filter 34, preferably a semi-permeable membrane. The other end of the 
pipette 30 is provided with a sealing cap 36. Additionally the needle 32 
and mounting 37 therefor is removable from the syringe body 31 so that a 
sealing cap 38 is sealingly locatable on the inlet extremity on the 
syringe body 31. 
In operation of the above described pipette and syringe assembly, blood is 
drawn into the syringe by telescopic outward movement of the pipette 30 
from within the syringe body 31. Thereafter the needle 32 is removed and 
the cap 38 placed on the inlet end of the body 31 so as to sealingly close 
the inlet. The pipette 30 and syringe body 31 is then centrifuged so as to 
separate the blood cells from the plasma. To then remove the plasma from 
within the syringe body 31, the cap 36 is removed and the pipette 
telescopically removed within the syringe body 31 so as to locate the 
plasma within the interior of the pipette 30. The plasma may then be 
dispensed from within the pipette 30 by resiliently deforming the side 
walls of the pipette 30 to expel the plasma from the tapered outlet 35. 
Preferably the pipette 30 would be formed of resilient plastics material to 
allow resilient deformation of the walls to expel the plasma from within 
the pipette. Additionally the pipette 30 may need to be reinforced by 
resilient ribs so that it may successfully operate as a piston when 
co-operating with the internal surfaces of the syringe body 31.