The document discusses the Coulter principle for counting and differentiating blood cells using electrical impedance. The sample is divided and mixed with diluent before being delivered to red blood cell (RBC) and white blood cell (WBC) apertures. RBCs and platelets are counted in the RBC aperture based on their size. In the WBC aperture, a lysing reagent is added to lyse RBCs before WBCs are counted. Hemoglobin is also determined using light transmittance.

1. CBC- Coulter Principle
Caesar Abu Arra
MSc Life sciences
BSc Medical lab. Sciences
Medicare Labs

3. Electrical impedance: Coulter principle
The sample is divided into two aliquots and
mixed with an isotonic diluent:
1-The first dilution is delivered to the RBC aperture bath:
RBCs and the platelets are counted and discriminated by
electrical impedance
 Particles between 2 and 20 fL are counted as platelets.
 Those greater than 36 fL are counted as RBCs.

4. Electrical impedance: Coulter principle
2-The second dilution is delivered to the WBC aperture bath:
 Lysing reagent is added to the WBC dilution to lyse RBCs 
release hemoglobin (before the WBCs are counted)
 WBCs are counted by electrical impedance.
 The WBC dilution is passed to the hemoglobinometer for
hemoglobin determinationlight transmittance at a
wavelength of 535 nm.
 The analyzer automatically cleans the remaining blood by
cleaning reagent.

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