Pipettes are the laboratory equipment used for handling liquid samples. Almost all the pipettes require pipette tips for performing their intended work.
Pipette tips are the attachable part of pipettes that aid in aspirating and dispensing liquids. Most commonly used tips are disposable or autoclavable. These are also available in various types like non-sterile or one-time use (used for general laboratory procedure), pre-sterile (used for cell cultures), and filtered tips (used for handling RNA and DNA) .
Pipette tip made up of virgin polypropylene is the most common and environmental friendly one. Sometimes the tips also contain plastics or metal additives (yellow and blue colored tip).
Pipette tips from Eppendorf and Thermofisher are most commonly used in any laboratory, and these companies also provide almost all types and sizes of pipette tips.
Types of Pipette Tips
The pipette tips are divided into several types based on their functions and properties. One basis for differentiating the types of pipettes is sterility. Some tips might be sterile and RNase-free (filter tip). In contrast, non-sterile tips are generally autoclavable and useful in simple laboratory experiments like serological tests.
Another basis is their purpose; some require a more extended head to prevent contamination (long tip) or may require precise measurement (low retention tips). Finally, the last basis for differentiation is size; 0.1 to 1000 µl is available in universal (non-sterile) pipette tips.
The types of tips and their functions are as follows:
Based on sterility
Sterile or Pre-sterile Tips
These are one-time use tips that come in the pre-sterilized form. These tips are free of DNA, RNase, ATP, and pyrogens and suitable for experiments that require sterile conditions like cell cultures, PCR, etc. These are also helpful while handling volatile liquids and specimens that require testing in a contamination-free environment.
These are the most commonly used tips, and also known as universal or general purpose pipette tips. These tips are not sterile because they are not certified as free of RNase, DNA, pyrogens, etc. These are applicable in simple laboratories for handling liquid specimens and reagents that are not volatile or do not have high contamination risk.
Based on purpose
Pipetting creates aerosols that carry the risk of cross-contamination. The filter tips are fitted with a filter to avoid the formation of aerosols. This type of pipette has been helpful in PCR (polymerase chain reaction), handling RNA/DNA, radio-labeled, infectious, and volatile samples.
These tips withhold less liquid than generally used ones, which help preserve samples/reagents. These tips are good for viscous and highly concentrated samples. However, these pipette tips are very costly. These are ideal for electrophoresis, protein analysis, sequencing, or any tests that use viscous and concentrated liquids.
Sometimes the reagents or samples have a minimal volume and are at the bottom of the container. It means putting not only the pipette tip but also the shaft of the pipette inside the container. This increases the risk of contamination, so using a pipette tip that is longer than usual ones is the best substitute.
The extended tips become inconvenient when the samples are drawn or placed into small wells. So, using short tips with a multichannel pipette is the perfect fit. Likewise, pipetting with long tips can strain the hands and require wider bench space. So, switching to shorter tips in order to avoid these conditions is the best option.
Wide Bore Tips
Sometimes the samples that a laboratory handles can be fragile and deteriorate while transferring from a narrow area of the standard tips. So, using tips with a wide orifice is the best option for handling samples involving cells or that are very dense.
Based on size
The pipette tips based on the size range from 0.1 to 1000 µl for non-sterile/general purpose pipettes. 200 µl and 1000 µl tips are used in serological tests and school laboratory experiments. Whereas for filter tips, these range from 0.1 to 1250 µl. These are available in bulk or a box.
Pipette tips packaging
The general purpose tips from Plastibrand are packaged in the bulk of 500-1000 tips in a bag. Also, there is packaging available in boxes of 60 to 500 tips in a box.
However, sterile tips from the same brand are packaged in boxes of 480-1000 tips in a box.
Uses of Pipette Tips
The tips are integral to any pipetting device, from manual to automated. The pipette tip helps to increase pipetting speed and prevent contamination. So, these have utmost use in the laboratory handling liquid samples.
Criteria for Choosing the Right Pipette Tip
The main criteria for choosing the right pipette tip is the experiment you conduct in your laboratory. Sterile filter tips are a must if you are attempting molecular tests in the laboratory. Along with the experiment, there are many more criteria to consider before buying the tips. They are as follows:
Volumes of Liquid Handled
The volume of liquid samples or reagents varies widely in the laboratories. In the laboratory, it is best to have tips of various sizes and purposes.
If you are handling multiple samples in a limited time, you might use a multichannel pipette. Still, general laboratories use micropipettes, so buying the tips suitable for both types in bulk is more economical.
If you opt for pre-sterile tip, you need to look for a company that provides the sterilization certificate. Similarly, non-sterile tips are reusable if the company states it as autoclavable. For example, Plastibrand has a bio-cert that claims the sterile pipette tip is free of ATP, endotoxins, DNA, and RNase after sterilizing it under the ISO 11 137 and AAMI guidelines.
Your budget is the second main criterion for choosing a suitable pipette for your laboratory. The filter tips are costly as compared to general-purpose tips. So, if the budget is tight and you are not willing to perform any molecular tests, then buying just general-purpose tips is the best choice.
Handling of Pipette Tips
Handling pipette tips is a crucial step in minimizing laboratory errors. Some points to consider while performing the laboratory work are as follows:
- Maintain the right temperature during storage and while performing tests. Bring the tip and all the equipment to room temperature.
- If you use general-purpose pipette tips, rinse it correctly with the sample/liquid you are aspirating to avoid delivering the incorrect volume of the liquid.
- Do not use your hands while removing or placing the pipette tips in the pipette to avoid cross-contamination.
- Pipetting technique should be standard. Press the plunger to the first stop and immerse it into the liquid to aspirate the sample. While dispensing, press the plunger up to the second stop (double press) to dispense all the liquid.
- Immersing the pipette tip up to the correct depth is also important.
- While aspirating the sample and pulling it out from the container, hold the pipette vertical.
- Check the pipette tips before and after dispensing, to ensure the liquid is dispensed completely.
- The force applied while pressing the plunger should be consistent.
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