Overview
This lecture introduces the different types of pipettes used in aseptic lab work, explaining their features, correct handling, and basic operating procedures.
Types of Pipettes
- Serological (blowout) pipettes have an etched or colored band indicating all liquid must be expelled for accurate measurement.
- Serological pipettes often contain a cotton plug to protect the pipetting device from contamination.
- Measuring or drain-out pipettes lack the etched band and may or may not include a cotton plug; liquid should not be blown out past the end.
- Both pipette types may measure up to 10 mL with 0.1 mL increments.
Using Pipetting Devices
- Attach the pipette to the pipetting device by inserting and gently twisting for a secure seal.
- The pipetting device plunger is used to draw in and expel liquid; avoid leaks by checking the seal.
- For blowout pipettes, start the plunger slightly above the bottom for extra pressure to expel the last drops.
Micropipettes
- Micropipettes can typically dispense 100–1000 microliters (μL); 1000 μL equals 1 mL.
- Volume is adjusted by twisting the plunger; never set outside the stated minimum or maximum range.
- Always use sterile, disposable tips when using micropipettes to prevent contamination.
Micropipette Operation
- Hold the pipette in your dominant hand, use your thumb for the plunger.
- The plunger has two stops; press to the first stop to aspirate liquid, and to the second stop to dispense all liquid.
- Obtain a sterile tip by pressing the pipette into a tip within the box and immediately replacing the lid.
- Eject the used tip with the ejector button—do not remove it by hand.
Key Terms & Definitions
- Serological Pipette — A pipette designed to be “blown out” for full volume delivery, marked by an etched band.
- Blowout Pipette — Another term for serological pipette, requiring all liquid to be expelled.
- Measuring (Drain-Out) Pipette — Pipette used to measure liquid without blowing out the last drop.
- Micropipette — Adjustable pipette for very small volumes (μL range), used with disposable tips.
- Plunger Stops — Two positions on the micropipette plunger; the first for aspiration, the second for dispensing.
Action Items / Next Steps
- Practice attaching both types of pipettes to the pipetting device.
- Review correct micropipette operation, especially using the two plunger stops.
- Always use proper sterile technique when handling pipettes and tips.