Pipette is a word of the French language that means ‘a small pipe’. They do the same function as the pipes i.e transfer of liquids. Pipettes are used to transfer calculated volumes of liquids from one container to another in a laboratory.
There are several different types of pipettes based on their specific functions to get maximum precision in the experiment. In this article, we will read what are pipettes, how to use a pipette, and types of pipettes.
What is the purpose of Pipettes
The scope of use of pipettes is very diverse. You can use a pipette for the following places
- In a school laboratory, you can use pipettes to transfer an acid or a base during chemical titrations.
- In a microbiology laboratory, you can use a pipette to transfer a specific buffer (chemicals that resist change in pH) during media preparation.
- In a Serology laboratory, You can use serological pipettes to transfer body fluids and viscous substances such as blood and serums for medical examinations.
How does a Pipette work
All pipettes work on the same principle; They make use of negative air pressure to aspirate( or suck) liquid into them. When no negative pressure is applied at the mouth or upper part of the pipette, then it dispenses the liquid.
There are different methods to aspirate and dispense liquids.
- The oldest method to aspirate a liquid is by mouth pipetting.
- Nowadays, pipettes come with bulbs that are pressed to aspirate or dispense liquid.
- The most modern method of pipetting is by using a pipettor. A pipettor is a machine that sucks in liquid upon pressing a button.
Modern pipettes are equipped with pumps, which provide better and accurate transfers of required volumes.
What are the different types of Pipettes
Here is a list of different types of pipettes based on their use, and their shapes.
These pipettes have two small continuous bands located on the upper end of the pipette. These pipettes will dispense even the last drop of liquid into the receiving container.
Do not confuse two small continuous bands with a single thick band which indicates the maximum capacity of the pipette.
Self-draining pipettes do not have two small bands on their upper end. They do not dispense the last drop of the liquid. The liquid moves out of the pipette by the action of gravity. You are advised not to blow the pipette to remove the last remaining drop of liquid.
These are the simplest pipettes. They have a bulb on their upper end which is pressed to fill the liquid into the bulb through suction pressure. The cylindrical bulb is pressed again to dispense the liquid.
It is advised to keep the pipette at a 90-degree angle while pipetting and at a 45-degree angle while dispensing it. Discard the pipette after one use.
These are the type of transfer pipettes with a bulb that are present at the lower end of the body. They are used in clinical laboratories for transferring viscous liquids such as serum and blood.
OF pipettes are blow-out pipettes.
These are the type of transfer pipettes that have a bulb in the center of the body. These pipettes have calibrations on them for the transfer of the exact volume of liquids. They are commonly used in quality-control labs.
Volumetric pipettes are self-draining.
A Mohr’s pipette is a measuring pipette. It looks just like a Volumetric Pipette with no bulb. It has a wider neck than a volumetric pipette, plus it has calibrations marked on its body till its tip. They provide less accuracy so are not recommended in experiments where high accuracy is required.
- A serological pipette is a measuring pipette with calibrations marked down till the end of tip.
- They are Blowout pipettes. They have a larger dispensing orifice than do Mohr’s pipette has thus the liquid moves down faster in them.
- They are commonly used for transferring small volumes of liquid (in millimeters).
- The volume of liquid dispensed is calculated by subtracting the final volume from the original volume present in the pipette.
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- These are reusable (case sensitive), medical-grade pipettes with calibrations on the body.
- They are used to transfer small amounts of liquids.
- They have a bulb on the upper end which helps in the aspiration and dispensing of liquid.
- A micropipette is a sophisticated instrument that can transfer accurate volumes of liquids up to the 1000th part of 1ml.
- They are used in microbiology labs and work on the principle of air displacement for optimum accuracy.
- Micropipettes are non-disposable because they use micropipette tips. Only the tip comes in contact with the liquid. The tip is discarded after use.
- They are also called single-channel pipettes. A micropipette has a push-button on top which helps to aspirate and dispense liquids.
- You can rotate the push-button to increase or decrease the volume of the liquid to be taken.
The two techniques involved in pipetting are
- Forward technique
It is a more commonly used technique. In this technique, press the plunger till soft push and then submerge the micropipette tip into the liquid. Release the plunger slowly to aspirate the liquid.
To dispense the liquid, place the tip by slightly touching it to the side of receiving vessel. Slowly push the plunger to soft push and then to then harder push to dispense all the liquid.
- Reverse Technique
This technique is used to minimize bubble formation while transferring viscous liquids. In this technique, press the plunger down to hard push, then slightly submerge the tip into the liquid and slowly release the plunger to aspirate the liquid.
To dispense the liquid, place the tip against the side of receiving vessel and press the plunger to soft push. Take the tip out of the vessel, there is some liquid still present in the tip but it is not the part of the measurement.
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- A multichannel micropipette is an advanced form of micropipette which can transfer up to 12 liquids at a time.
- Multichannel micropipette has 12 tips that can work simultaneously.
- Multichannel pipettes reduce the workload on the operator.
- They are used while working with 96-well plates (or ELISA plates).
A repeater pipette is a modified micropipette with the ability to dispense equal volumes of liquid again and again without the need to aspirate repeatedly. It saves the operator time and effort.
It has a different design than a typical micropipette. These pipettes allow the operator to aspirate the liquid only once and then dispense equal volumes into different vessels repeatedly.
An Eppendorf pipette is the same as a micropipette but it is specifically used to transfer to an Eppendorf tube. Eppendorf is the name registered against a leading international instrument manufacturing company.
What are Micropipette tips
Micropipette tips are transparent or semi-transparent disposable tips that collect the liquid which is to be transferred. They come in different colors and ranges so have their respective names.
The commonly used types of micropipette tips are as follows
- P10– These tips are transparent (white). They have a volumetric range between 0.5 to 10 microlitres.
- P20– These tips are yellow. They have a volumetric range between 2 to 20 microlitres.
- P200– These tips are yellow. They have a volumetric range between 20 to 200 microlitres.
- P1000– These tips are blue. They have a volumetric range between 200 to 1000 microlitres.
- P5000– These tips are also white. They have a volumetric range between 1000 to 5000 microlitres.
It is very important to use a specific type of tip according to the volume of the liquid. Using any other tip can affect the accuracy.
How to Clean Pipettes Properly
If an instrument is used frequently, it requires the same amount of maintenance to keep its optimal accuracy. Pipettes and micropipettes also need to be cleaned before they are reused.
There are some ways to properly clean your pipettes and micropipettes
- Using a household washing agent such as detergent for external cleaning.
- Use a long-ended cotton swab to clean the interior of the pipette and to remove any clogs.
- Micropipettes require a higher level of maintenance.
- To thoroughly clean a micropipette, use a detergent or washing agent for its external clean.
- A proper disassembly is required for thorough cleaning.
- Disassemble and then clean each part separately, slightly grease the pistons in the micropipette
- In case of any contamination in the micropipette, wash with 70% ethanol if the contaminant is an aqueous solution.
- For organic solvents, wash with detergent and air-dry.
- For proteins, use a detergent and air-dry.
- Do not use alcohol for proteins as alcohol sets the proteins.
- For any radioactive contamination, wash the micropipette with a solution like Decon and then air dry.
Frequently Asked Questions
Q1. How to use a pipette?
To use a pipette, just aspirate the required volume of liquid by pressing the bulb of the pipette, pressing the bulb of the pipette again to dispense the liquid.
Q2. How to read pipette measurements?
To take a reading on the pipette, elevate the pipette to eye level and take the reading on the lower meniscus of the liquid. Keep the pipette steady to minimize disturbance in the liquid.
Q3. Where should glass slides, pipettes, and capillary tubes be disposed of?
Glass instruments are considered as ‘sharp waste’. They must be disposed of through a bio-waste management company that discards them according to standard protocols. You can not dispose of them with common waste.
Q4. How many decimal places for pipette?
A measuring pipette can measure volumes up to 0.1 milliliters. A micro-pipette can measure and transfer liquids up to one-thousandth part of a milliliter, or you can say one microlitre.
Q5. Where to get pipettes from?
You can easily get pipettes from online stores like Walmart, Amazon, Daraz if you need them for your personal use in the laboratory.
If you need larger stock quantities of pipettes then you can directly contact the manufacturers such as Eppendorf AG, Thermo Fischer Scientific, and Mettler Toledo.
Q6. Why is it not safe to pipette by mouth?
Pipetting by mouth can be dangerous if the liquid is toxic or chemically hostile. You can accidentally pipette too hard that all the liquid gets into your mouth. It can lead to serious injuries.
If the liquid gets into your mouth, wash your mouth properly with water and seek medical assistance.
Q7. What is a pipette filler?
A pipette filler is anything that provides suction pressure so the liquid gets filled into the pipette. It can be any rubber bulb fitted to the upper end of the pipette.
There are electronic pipette fillers that have buttons on them to aspirate and dispense the liquid. They are battery-operated.
Q8. What is a plastic pipette?
A plastic pipette is a disposable pipette. You can not use it again and again just like a glass pipette. As they are used for the transfer of liquids that are infected so these pipettes are discarded after use to maintain biosafety protocols.