Diluting Blood with Unopette system

Diluting Blood with Unopette system


In some labs they use Unopette which is a prepared reservoirs containing 2 ml of isotonic solutions and small capillary tube prepared to withdraw 10μ blood.

Each capillary tube is specified to withdraw specific volume so, make sure that you get the one written on it 10



The Unopette procedure for counting red blood cells is as follows:

 Step One 

==> Puncture the diaphragm in the neck of the diluent reservoir with the tip of the capillary cover on the capillary pipette.

Puncturing the diaphragm of diluent with the capillary pipette shield.

 Step Two 

==> After obtaining free-flowing blood from a lancet puncture of the finger, or 10μl blood from whole blood from the tube, remove the protective plastic shield from the capillary pipette. (((Holding the capillary pipette slightly above the horizontal, touch the tip to the blood source))) (see the next picture).

==> The pipette will be filled by capillary action.

==> When blood reaches the end of the capillary bore in the neck of the pipette, filling is complete and will stop automatically.

==> The amount of blood collected by the capillary tube is 10 ml.

==> Wipe any blood off the outside of the tip of capillary tube, making sure that the wipes don’t touch the opening of the capillary tube to avoid absorption of blood by the wipes.

Drawing blood into the Unopette capillary tube:
A. From a finger puncture;
B. From a venous blood sample.

 Step Three 

==>  With one hand, gently squeeze the reservoir to force some air out, but do not expel any diluent.

==>  Maintain pressure on the reservoir.

==> With the other hand, cover the upper opening of the capillary overflow chamber with your index finger and seat the capillary pipette holder in the reservoir neck .

Preparing reservoir to receive blood from the capillary tube.

 Step Four 

==> Release pressure on the reservoir and remove your finger from the overflow chamber opening.

==>  Suction will draw the blood into the diluent in the reservoir

because when you press on the reservoir some air goes out and when you seat the capillary holder to the reservoir opening while your index finger cover the capillary holder opening, the air will not back to the reservoir, but when you release the pressure and remove your index finger from thr openning of the capillary holder, the air will enter to the reservoir through the capillary tube which push the blood into the reservoir and mix the blood with the isotonic solution

 Step Five 

==> Squeeze the reservoir gently two or three times to rinse the capillary tube, forcing diluent into but not out of the overflow chamber, releasing pressure each time to return diluent to the reservoir.

==> Close the upper opening with your index finger and invert the unit several times to mix the blood sample and the diluent.

Mixing blood sample and diluent.

For specimen storage, cover the overflow chamber of the capillary tube with the capillary shield.

 Watch this video to see the dilution by the Unopette system


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