SOP-021: Operation of Micropipettes
Purpose
To ensure accurate, precise, and reproducible liquid handling using adjustable micropipettes during mammalian cell culture procedures.
Scope
This SOP applies to the routine use of air-displacement micropipettes for transferring liquids during mammalian cell culture and related laboratory procedures.
Responsibilities
The operator is responsible for:
- Selecting the appropriate micropipette for the required volume.
- Using sterile pipette tips.
- Operating the pipette correctly.
- Preventing contamination of samples and equipment.
- Reporting damaged or malfunctioning pipettes.
Required Materials
Equipment
- Adjustable micropipettes
- Sterile pipette tips
- Laboratory wipes
- Pipette stand
- Biohazard waste container
Procedure
1. Select the Appropriate Pipette
Choose a micropipette whose operating range includes the desired transfer volume.
Avoid using a pipette at volumes outside its specified range.
2. Set the Volume
Adjust the volume using the adjustment dial.
Verify the displayed volume before attaching a pipette tip.
3. Attach a Sterile Tip
Firmly attach a sterile pipette tip.
Ensure the tip is securely fitted before use.
Do not touch the tip with bare hands.
4. Aspirate the Sample
Press the plunger to the first stop before immersing the tip into the liquid.
Immerse only the tip sufficiently below the liquid surface.
Release the plunger slowly and smoothly to aspirate the sample.
Inspect the tip for bubbles.
5. Dispense the Sample
Place the tip against the wall of the receiving vessel when appropriate.
Press the plunger smoothly to the first stop, then continue to the second stop to dispense the remaining liquid.
Withdraw the tip while maintaining pressure on the plunger.
Allow the plunger to return slowly after removing the tip.
6. Discard the Tip
Eject the used tip directly into an appropriate waste container.
Use a fresh sterile tip for each sample or reagent.
7. Store the Pipette
Return the pipette to its stand after use.
Set adjustable pipettes to their recommended storage position according to laboratory policy.
Acceptance Criteria
| Parameter | Acceptance Criterion |
|---|---|
| Pipette selection | Appropriate for transfer volume |
| Tip attachment | Secure |
| Liquid transfer | Smooth without bubbles or leakage |
| Pipette condition | Clean and undamaged |
Critical Control Points
- Select the correct pipette for the required volume.
- Aspirate and dispense slowly to improve accuracy.
- Keep the pipette vertical during aspiration.
- Change tips between samples.
- Never lay a pipette containing liquid on the laboratory bench.
Documentation
Record the following when required:
- Date
- Procedure performed
- Pipette identification (if applicable)
- Operator initials
Quality Control
Verify:
- Pipette is clean.
- Tip is securely attached.
- No leakage occurs during aspiration or dispensing.
- Volume setting is correct.
- Pipette operates smoothly.
Troubleshooting
| Observation | Possible Cause | Corrective Action |
|---|---|---|
| Inaccurate volume | Incorrect pipette selected | Use a pipette appropriate for the required volume |
| Air bubbles in tip | Rapid aspiration | Aspirate more slowly while keeping the pipette vertical |
| Liquid leakage | Loose or damaged tip | Replace the pipette tip and repeat the transfer |
| Sticky plunger | Pipette contamination or wear | Remove the pipette from service and inspect according to laboratory procedures |
Safety Considerations
- Wear appropriate personal protective equipment (PPE).
- Treat all biological samples as potentially hazardous.
- Never mouth pipette.
- Dispose of used pipette tips as biohazardous waste when applicable.
- Clean the exterior of the pipette if contamination occurs.