If you are an analyst, you notice some complex nature of liquids to pipet, such as acetone, blood, liquids with foam, etc. These liquids are a problem to achieving good precision and accuracy.
These troublesome liquids are a challenge to consider within laboratory operations. It is important that you aware of them and what you are facing, whether you have a pipette that works under the principle of positive displacement or air displacement.
One of the best instruments to take and measure these liquids is the micropipette. Positive Displacement Micropipettes, Air Displacement Micropipettes, and Semi-Automatic Pipetting Systems are classifications of micropipettes. These are inexpensive, easy to obtain, have good precision and accuracy, and easy to calibrate.
In this post, you will learn how to measure complex liquids using micropipettes.
Let us begin!
Measurement of difficult Liquids
You may encounter high resistance to the flow of viscous liquids. When dispensing a volume amount is finished, a small amount remains adhered to the inside surface of the pipette tip like TECAN Filter Tips. This affects the precision and accuracy of the measurement since the total suction volume is not dispensed.
If an air displacement micropipette is used, it is advisable to perform the reverse dispensing method. In addition, you must perform the dispensing slowly so as not to generate foam.
If a direct or positive displacement pipette is used, you don’t have to worry about this detail. It would help if you make a regular dispensing according to this instrument. (Brudenell, 2020)
The density of the liquid can influence the air chamber of conventional micropipettes. Liquids with low densities decrease the volume of the air chamber.
This causes a more significant than the true volume of fluid to be sucked in. Therefore, the dispensed volume will be higher. The opposite occurs when working with liquids with densities greater than that of water.
In both cases, you may face a systematic error that affects the accuracy of the measurement. If you work with air displacement micropipettes, you can adjust the pipette to the particular liquid using TECAN tips.
Otherwise, the positive displacement micropipette does not face problems with this type of samples. (Microlit, 2021)
Liquids with a vapor pressure greater than water also affect the air chamber of air displacement micropipettes. This is because the pressure from the steam generated increases the volume of the air chamber. In addition to this, the liquid is susceptible to evaporation, causing dripping at the TECAN tip of the micropipette.
In the case of the air displacement micropipette, you must moisten the tip of the pipette at least five times. After this, it performs the reverse dispensing method. This improves accuracy, however, dripping persists in the instrument.
Using a positive displacement micropipette eliminates this drawback. (Lab People, 2021)
Liquids such as blood can generate water vapor that carry viruses, bacteria, or small particles with them. These aerosols can enter inside of the micropipette, so that they can pollute both the instrument and the operator.
So, it is advisable to use 1000ul Conductive Filter Tips by TECAN with high-efficiency filters for air displacement micropipettes. Positive displacement micropipette tips securely enclose liquid. In this case, you do not require any accessory or a different method. (Microlit, 2020)
Liquids with detergents
Detergents lower the water’s surface tension. This causes a very thin layer of liquid to stick to the inner surface of the micropipette tip. This leads to the volume dispensed varying from one pipetting to another. Therefore, the measurement’s reproducibility decreases.
If you work with air displacement micropipettes, low retention TECAN tips are a solution to the problem. These tips have hydrophobic properties, that is, they repel water.
This feature prevents the formation of the liquid layer on the micropipette tip. Therefore, reproducibility is improved, and sample loss is reduced.
In the case of the positive displacement micropipette, the tip is cleaned by moving the piston. This is an option for more reliable and reproducible results. (Conductscience.com, 2021)
You can improve your laboratory practices when facing difficult liquids by applying air displacement and direct displacement micropipettes. MBP INC provides the highest quality TECAN Filter Tips and many other lab consumables to ensure you achieve good precision and accuracy.
Brudenell, S. (2020). How can I pipette highly viscous samples? – The Laboratory People. Retrieved 4 November 2021, from https://camblab.info/how-can-i-pipette-highly-viscous-samples/
Conductscience.com. (2021). Pipettes – Conduct Science. Retrieved 4 November 2021, from https://conductscience.com/specimen-lab/glassware/pipettes/
Lab People. (2021). Types of Liquids for Your Pipettes – Tips for a Successful Transfer. Retrieved 4 November 2021, from https://www.labpeople.com/blog/types-of-liquids-for-your-pipettes-tips-for-a-successful-transfer/
Microlit. (2020). Filter Tips are an essential part of Covid19 Testing. Retrieved 4 November 2021, from https://www.microlit.us/filter-tips-are-an-essential-part-of-covid19-testing/
Microlit. (2021). What is the difference between air displacement and positive displacement pipettes?. Retrieved 4 November 2021, from https://www.microlit.us/what-is-the-difference-between-air-displacement-and-positive-displacement-pipettes/