A Comprehensive Guide on Mastering Pipetting Technique

In laboratory work, accuracy and precision are crucial for reliable results and efficient use of valuable reagents. Among the essential skills for scientists and lab technicians, pipetting is a fundamental technique. Precise pipetting not only ensures valid and reliable results but it also minimizes wastage of often costly reagents. 

This blog post will provide information about the popular Pipetting Technique used in the laboratory and discuss the best practices for pipetting. 

Which Pipetting Technique is Commonly Used in the Laboratory?

Pipetting is a technique used in laboratories to measure and transport a specific volume of liquid. The process is carried out using a tool known as a pipette, which functions like a dropper. This technique is essential in various scientific disciplines, including chemistry, biology, and medicine, where precise and accurate measurement of liquids is crucial. 

Pipetting can be manual or electronic, and the selection depends on the specific task. But manual pipetting is commonly used in laboratories. 

Two types of pipetting are as follows:

Manual Pipetting

The Manual Pipetting Technique is the most basic and commonly used. It involves using a handheld pipette to aspirate and dispense liquids. The operator controls the volume and movement of the pipette manually. Manual pipetting is suitable for routine laboratory work and is available in various types, such as single-channel and multi-channel pipettes.

Electronic Pipetting

Electronic pipettes, also known as motorized or automatic pipettes. They have an electronic motor for aspirating and dispensing liquids. They provide precise and accurate pipetting. Electronic pipettes often have programmable functions, such as multiple dispensing, mixing, and serial dilution.

Here are some other types of pipetting techniques which can be used in the laboratory: 

Forward Pipetting

This is the most common Pipetting Technique used for routine transferring of liquids. The process involves using a pipette to collect liquid and then transferring it to a new container.

• First, press the plunger of the pipette down until you feel it stop. Dip the pipette tip into the liquid, ensuring it's immersed but not too deep. 
• Slowly release the plunger to collect the liquid into the pipette. Remove the pipette from the liquid, wiping any excess off the outside of the tip. 
• Transfer the liquid into the new container by pressing the plunger to the first stop, wait a moment, and then press to the second stop to expel any remaining liquid.

Reverse Pipetting

This technique helps handle volatile, viscous, or foaming liquids and pipetting minimal volumes where maximum precision is required.  This pipetting involves dispensing an excess volume of liquid first and then withdrawing a smaller volume back into the tip. This compensates for any potential liquid loss during dispensing. 

• For Reverse Pipetting, depress the plunger to the second stop. 
• Dip the pipette tip into the liquid and slowly release the plunger to aspirate more than the set volume. 
• Remove the pipette from the liquid, wiping any excess off the outside of the tip. 
• Dispense the liquid into the new container by pressing the plunger to the first stop. The excess liquid remains in the tip. 
• Do not press to the second stop - discard the remaining liquid with the tip.

Serial Dilution Pipetting

This Pipetting Technique is used in the laboratory to create a series of solutions with decreasing substance concentrations. It involves transferring a small volume of a solution into a larger volume of diluent to achieve the desired dilution factor. This technique is usually used in biochemical and microbiological procedures.

For serial dilution pipetting, draw up a certain amount of the solution in the pipette. Add the stock solution to a new container with a known volume of diluent and mix thoroughly. Aspirate a volume of the first dilution, and then add it to a second container with diluent. Repeat the process to achieve the desired dilutions.

Repeat Dispensing

This Pipetting Technique is used when dispensing the same volume of liquid multiple times is required. This technique is efficient for processes such as filling multi-well plates.

Repeat pipettes have a dial or a digital display that allows the user to set the desired volume. After aspirating the liquid, the pipette can be placed to dispense the exact volume repeatedly without requiring multiple aspiration steps.

Multichannel Pipetting

Multichannel Pipettes are designed to pipette multiple samples simultaneously. They typically have 8, 12, or 16 channels, allowing for efficient and rapid dispensing of liquids into various microplate wells or other multi-well formats. This Pipetting Technique is useful in high-throughput applications.

Air Displacement Pipetting

Air displacement pipetting is used in laboratories to measure and transfer liquid volumes using pipettes accurately. It involves utilizing air displacement within the pipette to draw up and dispense the liquid. Air displacement pipettes are versatile and suitable for a wide range of applications. They are available in various volume ranges, from microliters to milliliters.

Best Tips for Pipetting

Pipetting is a crucial technique in the laboratory, and its accuracy significantly impacts the success of your experiments. Regular calibration and maintenance of pipettes and suitable pipetting methods are essential for accuracy and precision.  The best practices for accurate pipetting are as follows:

Rinse the Pipette Tip

Pipette accuracy can be improved by pre-rinsing the pipette tip with dispensing liquid. This step is significant when using air displacement pipettes as it conditions the air within the pipette tip to the temperature of the liquid. Labware Cleaning Supplies can be helpful in the proper cleaning and maintenance of pipettes. 

Proper Angle of Pipetting

Hold the pipette vertically while aspirating. However, when dispensing into shallow vessels, the pipette should be held at an angle to allow the tip to touch the vessel's side. Moreover, always use the correct and quality pipette tips. Refrain from unfitting or low-quality tips can lead to inaccuracies and contamination.

Smooth Operation

Aspiration and dispensing of liquids should be done smoothly and consistently. Jerky movements can lead to the formation of air bubbles which can significantly affect the accuracy of the measured volume.

Regular Calibration

Regularly calibrate pipettes to ensure they are functioning correctly. A well-maintained and calibrated pipette contributes significantly to pipetting accuracy.

Environmental Considerations

Be aware of the temperature and altitude where you work, as they can impact the volume of liquid delivered.

By mastering these pipetting techniques and adopting these best practices, you can improve the accuracy and precision of your lab work. Explore laboratory equipment at Westlab Australia, a reputable lab product supplier, to enhance your techniques. Get high-quality multichannel, serological, and volumetric pipettes at Westlab Australia. Visit our website now and shop pipettes to elevate the standards of your laboratory experiments!