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SOP-020: Operation of a Hemocytometer

Purpose​

To ensure the accurate and reproducible use of a hemocytometer for manual cell counting and viability assessment of mammalian cell cultures.

Scope​

This SOP applies to manual cell counting using a standard hemocytometer for adherent and suspension mammalian cell cultures.

Responsibilities​

The operator is responsible for:

  • Preparing a representative single-cell suspension.
  • Loading the hemocytometer correctly.
  • Following standardized counting rules.
  • Cleaning and storing the hemocytometer after use.

Required Materials​

Reagents​

  • Cell suspension
  • Trypan Blue or other viability dye (if applicable)

Equipment​

  • Hemocytometer
  • Hemocytometer coverslip
  • Micropipettes and sterile tips
  • Inverted microscope
  • Lens tissue or lint-free wipes
  • 70% ethanol

Procedure​

1. Inspect the Hemocytometer​

Before use, verify that:

  • The counting chamber is clean.
  • The coverslip is free of scratches or residue.
  • No cracks or damage are present.

2. Prepare the Sample​

Prepare a well-mixed single-cell suspension.

If viability assessment is required, prepare the sample according to the laboratory counting protocol.

Mix the suspension gently before loading.

3. Load the Hemocytometer​

Place the coverslip correctly over the counting chamber.

Load the sample slowly at the edge of the chamber using a micropipette.

Allow the chamber to fill by capillary action.

Avoid:

  • Air bubbles
  • Overfilling
  • Underfilling

4. Examine the Sample​

Place the hemocytometer on the microscope stage.

Focus using the appropriate objective.

Verify that:

  • Cells are evenly distributed.
  • The grid is clearly visible.
  • No large aggregates interfere with counting.

5. Perform Cell Counting​

Count cells according to the laboratory's established counting method.

Maintain the same counting rules throughout the procedure.

If duplicate chambers are used, compare the results before proceeding.

6. Clean the Hemocytometer​

Discard the sample appropriately.

Clean the hemocytometer and coverslip with distilled water followed by 70% ethanol if required.

Dry with lint-free tissue.

Store the hemocytometer in its protective case.

Acceptance Criteria​

ParameterAcceptance Criterion
Chamber loadingEven without bubbles
Cell distributionUniform
Grid visibilityClear
Duplicate countsComparable between chambers

Critical Control Points​

  • Thoroughly mix the cell suspension immediately before loading.
  • Do not overload the counting chamber.
  • Avoid introducing air bubbles.
  • Use consistent counting rules throughout the procedure.
  • Clean the hemocytometer immediately after use.

Documentation​

Record the following:

  • Date
  • Cell line
  • Sample identification
  • Cell concentration
  • Cell viability (if assessed)
  • Operator initials

Quality Control​

Verify:

  • Hemocytometer is clean before use.
  • Coverslip is correctly positioned.
  • Cell suspension is homogeneous.
  • Duplicate counts are reproducible.
  • Equipment is cleaned after use.

Troubleshooting​

ObservationPossible CauseCorrective Action
Uneven cell distributionSample not adequately mixedGently resuspend the sample before reloading
Air bubbles presentImproper loading techniqueReload the chamber using capillary action
Chamber overfilledExcess sample volumeClean the chamber and reload correctly
Poor reproducibilityInconsistent counting methodRepeat the count using standardized counting rules

Safety Considerations​

  • Wear appropriate personal protective equipment (PPE).
  • Handle all cell suspensions as potentially biohazardous.
  • Dispose of biological waste according to institutional procedures.
  • Clean and disinfect the hemocytometer after each use.
  • Handle the glass hemocytometer carefully to prevent breakage.