Figure 2-1. Hematological pipets.
Whole blood
= 0.5 = 1
Dilution = Volume in bulb
10
20
and in the RBC count
Whole blood
= 0.5 = 1
Dilution = Volume in bulb
100 200
The dilution of the blood sample in the white blood count is 1 to 20 and the dilution
factor is 20. In the red blood count the blood sample is diluted 1 to 200 and the dilution
factor is 200. The permissible error of the red cell pipet is +5 percent and the white cell
pipet has a permissible error of +3.5 percent.
d. Blood cell diluting pipets are delicate pieces of equipment and should have
careful treatment. It is also important that clean, dry diluting pipets be used to prevent
dilution errors and hemolysis of cells.
e. If an aspirator is available, pipets can be easily washed by drawing cold tap
water (distilled water is preferred) through the pipet. If a deposit remains, it can be
dissolved by drawing dilute sodium hypochlorite (household bleach) through the pipet
followed by several washings with distilled water. If pipets become plugged through
neglect, the hole may be opened with a fine steel wire, and the above procedures may
then be carried out. When necessary, pipets may be dried rapidly by drawing a small
amount of alcohol through then and then ether or acetone followed by a stream of air
until the glass bead removes freely and no moisture remains in the pipet.
MD0853
2-4