Introduction
Pipettes are essential tools in any biochemistry or biology laboratory. They are used to measure and transfer precise volumes of liquids, from a few microliters to several milliliters. The correct use of pipettes ensures accuracy and reproducibility in experimental work. There are different types of pipettes available, each with unique features and applications. This answer describes the various types of pipettes and how they are used.
Main Types of Pipettes
1. Volumetric Pipette
- This pipette is designed to deliver a fixed, accurate volume of liquid.
- It has a single graduation mark and a bulb in the center to hold liquid.
- Common sizes include 1 mL, 5 mL, 10 mL, etc.
- Use: Best used when a highly accurate measurement of a single volume is required, such as in preparing standard solutions.
2. Graduated Pipette (Measuring Pipette)
- This pipette has graduation marks along its length.
- It can measure and deliver different volumes, depending on how much liquid is drawn up.
- Available in various sizes like 1 mL, 5 mL, 10 mL, etc.
- Use: Suitable for measuring various liquid volumes with moderate accuracy.
3. Serological Pipette
- A type of graduated pipette with calibration marks all the way to the tip.
- It is usually used with a pipette aid or pipette pump.
- It must be blown out completely to deliver the full volume (marked as TD = To Deliver).
- Use: Commonly used in cell culture, media preparation, and transferring liquids.
4. Micropipette
- Micropipettes are precision instruments used to measure and transfer very small volumes, typically in the microliter (µL) range.
- There are fixed and variable-volume micropipettes (e.g., 0.5–10 µL, 20–200 µL, 100–1000 µL).
- They use disposable plastic tips to avoid contamination.
- Use: Ideal for molecular biology, PCR, enzyme reactions, and other experiments requiring small liquid volumes.
5. Pasteur Pipette (Dropper)
- Made of glass or plastic, this pipette is used for transferring liquids in drop-wise amounts.
- It does not have any graduation marks and is not used for precise measurements.
- Use: Transferring reagents, adding indicators, or qualitative experiments.
6. Electronic Pipette
- Battery-operated or electronic-controlled pipette for high-precision liquid handling.
- Reduces hand strain and user error.
- Use: Automated tasks, high-throughput labs, and long pipetting sessions.
Proper Usage of Pipettes
- Always use the correct type of pipette for the required volume.
- Use a pipette bulb or pump for drawing liquids — never use your mouth.
- Hold the pipette vertically while measuring.
- Read the meniscus at eye level for accurate volume reading.
- Micropipettes must be held steadily and used with the right-sized tips.
- Clean the pipette after use to avoid cross-contamination.
Calibration and Maintenance
- All pipettes must be regularly calibrated for accuracy.
- Check for leaks or damage, especially in micropipettes.
- Store vertically or in pipette stands to prevent contamination or breakage.
Conclusion
Understanding the types of pipettes and their proper use is essential for accurate and effective laboratory work. From volumetric and graduated pipettes to micropipettes and electronic models, each type serves specific functions. Proper handling, calibration, and maintenance of pipettes help ensure reliable and reproducible experimental results in biochemistry and related fields.