Pipettes – Principle, Types, Uses, Parts, Operation, Advantages & Precautions

Pipettes are laboratory instrument used to measure and transfer small volumes of liquid with high accuracy. Pipettes are essential in biology, chemistry, medical research, food analysis, and biotechnology. They come in different types—glass, plastic, and electronic—and range in capacity from a few microliters (µL) to several milliliters (mL).

The term “pipette” comes from the French word pipette, meaning “small pipe.” Whether you are preparing a PCR sample, conducting a titration, or culturing cells, pipettes ensure that liquids are handled with precision, safety, and reproducibility.

Principle of Pipettes

Pipettes work mainly on two principles:

1. Air Displacement Method

Used in most laboratory pipettes.
A piston inside the pipette moves up and down, creating an air cushion between the piston and the liquid.
When the piston is pressed, air is expelled; when released, the vacuum draws liquid into the tip.
Advantages: Suitable for general lab work; allows control over pipetting speed and force.

2. Positive Displacement Method

Common in specialized or repeater pipettes.
The piston is in direct contact with the liquid—no air cushion.
Ideal for viscous or volatile liquids that are hard to measure with air displacement pipettes.

Main Parts of a Pipette

Components of Pipettes; Main parts of Pipettes — **Figure:** Main parts of a Pipette

Plunger – Aspirates and dispenses liquid.
Ejector Button – Discards the pipette tip safely.
Volume Adjustment Knob – Sets the desired volume (not present in fixed-volume pipettes).
Volume Window – Displays the selected volume.
Shaft – Hollow tube that connects plunger to tip.
Tip Cone – Attaches pipette tip securely.
Pipette Tip – Disposable plastic tip that holds the liquid.

Types of Pipettes

1. Pasteur Pipettes

Also called eye droppers.
Traditionally made of glass; now often plastic.
Used for transferring small liquid volumes without precision measurement.

2. Volumetric Pipettes

Also called bulb pipettes.
Used for preparing solutions for analytical chemistry and titrations.
Highly accurate – up to four significant digits.

3. Graduated Pipettes

Have markings to measure variable volumes.
Include:
- Serological Pipettes – Used for cell suspensions, gradients, and mixing.
- Mohr Pipettes – Less precise; used when high accuracy is not essential.
- Transfer Pipettes – Disposable, plastic, used to avoid glass breakage and contamination.

4. Vacuum-Assisted Pipettes

Operated using suction devices.
Made from polystyrene, glass, or borosilicate.
Used in cell culture and sterile liquid handling.

5. Repeater Pipettes

Dispense the same volume repeatedly without refilling.
Speeds up repetitive tasks in ELISA and microplate assays.

6. Single vs. Multichannel Pipettes

Single-Channel Pipettes – One tip; ideal for tubes or individual wells.
Multichannel Pipettes – Multiple tips; used for microplates (8, 12, or more channels).

7. Manual vs. Electronic Pipettes

Manual Pipettes – Operated by thumb; economical.
Electronic Pipettes – Battery-powered; more ergonomic and precise.

8. Fixed vs. Adjustable Volume Pipettes

Fixed Volume – For repetitive use of the same volume; faster and less error-prone.
Adjustable Volume – Flexible; can change settings for different experiments.

9. Special Purpose Pipettes

Designed for specific applications like environmental hormone analysis or ultra-micro volume dispensing.
Examples: Van Slyke pipettes, Ostwald-Folin pipettes, glass micropipettes, microfluidic pipettes.

How to Use a Pipette

Attach Tip – Take a sterile tip from the box and fit it securely.
Set Volume – Adjust using the dial.
Aspirate Liquid – Press plunger to the first stop, immerse tip, and slowly release.
Dispense Liquid – Place tip in receiving container and press plunger to second stop.
Eject Tip – Press ejector button into waste bin.

Applications of Pipettes

Biological Research – DNA extraction, PCR setup, ELISA.
Cell Culture – Even cell seeding, media exchange, reagent addition.
Clinical Diagnostics – Blood analysis, sample preparation.
Pharmaceutical Labs – Drug formulation and quality control.
Food & Environmental Testing – Sample analysis for contaminants.

Advantages of Pipettes

High accuracy and precision.
Easy to handle for both beginners and experts.
Compatible with a wide variety of liquids.
Safer than pouring hazardous chemicals.
Electronic and multichannel pipettes improve speed in high-throughput experiments.

Limitations of Pipettes

Volumetric pipettes can be costly.
Graduated pipettes less precise.
Requires regular calibration to maintain accuracy.

Precautions while using Pipette

Never use mouth pipetting.
Always use the correct tip size.
Avoid dropping pipettes to prevent calibration loss.
Store pipettes vertically when not in use.
Wear gloves to avoid contamination.

Popular Pipette Examples

Haier Biomedical PIP Series – Serological pipettes for tissue culture.
IKA Pette Vario – Manual adjustable pipette with ergonomic grip.
Eppendorf Xplorer® – High-precision electronic pipette.
Bioevopeak PIPE-M12 – Multichannel manual pipette.
Vitlab Pasteur Pipette – Disposable transfer pipette for aliquoting liquids.

Frequently Asked Questions (FAQ)

Q1. What is the difference between micropipettes and pipettes?
Micropipettes handle volumes in microliters; regular pipettes handle milliliters.

Q2. How often should pipettes be calibrated?
At least once every 6 months for high-accuracy work.

Q3. Which pipette is best for viscous liquids?
Positive displacement pipettes.

Q4. Can pipette tips be reused?
Only if they are designed for reuse and sterilized properly.

Q5. What is the most accurate pipette type?
Volumetric pipettes are generally the most accurate.

References

Aqlan, F., Huang, Y., Walters, E.G., & Meanazel, O.T. (2017). Enhancing ergonomic design skills among undergraduate students by integrating Computer Aided Design and Digital Human Modeling.
https://solutions.pipette.com/pipette-types/
https://www.labcompare.com/General-Laboratory-Equipment/1265-Pipettes-Micropipettes/
https://www.labmate-online.com/news/laboratory-products/3/breaking-news/a-brief-guide-of-pipette-types/30746
https://www.nichiryo.co.jp/en/productline/pipette.html
https://www.thermofisher.com/np/en/home/life-science/lab-plasticware-supplies/lab-plasticware-supplies-learning-center/lab-plasticware-supplies-resource-library/fundamentals-of-pipetting/liquid-handling-selection/pipette-types-for-different-applications.html