Choosing the correct tip for your pipettes: are third-party manufactured tips a good alternative?
by Dr Nicolas Gerst
Pipettes are important tools widely used in the lab. They are usually chosen and purchased carefully with the goal of receiving the best performance for a given price. Pipette tips are consumables; therefore, price can be an important factor, sometimes at the detriment of quality and performance. We found that tips from pipette manufacturers performed as expected but certain third-party manufacturer products performed just as well.
Introduction
Have you ever wondered if you are using the correct tip for your pipette? There are several articles warning users that inaccurate pipetting is often caused by using the incorrect tip [1, 2]. Most pipette manufacturers sell pipette tips so the choice should be easy, right? Well, that may not always be the case. To be on the safe side you just automatically buy the same brand tips as the brand of your pipette, not even taking into consideration third-party manufactured options. However, you should not make your buying process this straight forward.
Many laboratories use multiple brands of pipettes. Pricing is often a driving factor for using various options, with the goal of researchers and lab managers being to purchase a tip that works well for all pipettes at a reasonable price. In this article we will explore the results of an experiment we conducted comparing pipette manufacturer tips versus third-party tips.
One tip for all pipette brands
Lab managers and researchers question whether they can use one type of tip for all their different pipettes. Our experiment tested tips from pipette manufacturers and third-party manufacturers on three different pipette brands (Gilson, Sartorius and ThermoFisher). The pipettes used in this study are manual single channel pipettes. With every user the random error may be affected by the user’s pipetting technics. Muriel Art et al. use an electronic pipette for their test bringing more consistency between each pipetting [1]. Manual pipettes are widely used by researchers; therefore, it is important to test these too [3].
Material and methods
We used three pipettes from the following different original manufacturers (Gilson, Sartorius and ThermoFisher Scientific).
- Finnpipette™ 200 μl (ThermoFisher Scientific; serial no. CH38384)
- BioHit mLine® m200 (Sartorius; serial no. 7518885)
- PIPETMAN® Classic P100 (Gilson; serial no. L14257L)
The performance of the combination of pipette and tip was determined using the gravimetric method with a Practum® 224-1S analytical balance (Sartorius). We set up the experiment in a room free of draft with a relative humidity above 45% and a constant temperature (between 15 °C and 25 °C). Humidity, temperature and atmospheric pressure were measured during each experiment to calculate the Z factor, which is used in the calculation of water volume and needed for pipette calibration. The measurements (ten) were performed at 10% and 100% nominal volumes with or without a tip change.
We calculated the systematic error and the random error according to the formula found in the manual of the pipettes. Also, the formula is the same for all the pipettes, the error limits are different and will be used in the graph later on (red line).
Details of the different tips used in this study are shown in Table 1, and they were all bought in bulk.
Regarding packaging, tips A, B and C came in a box that was well labelled (size, plastic type, expiration date). Tips D and E came in a bag, also well labelled. Tips F and G came in a bag with a small sticker with a number (maybe a lot number). All the tips are clear except for tip G, which has a yellow colour.
Results
The tips were ranked from least expensive to most expensive: G < F < E < B < A < D < C. There is a factor of four between the least expensive and the most expensive tip (Table 1). The results for the BioHit pipette are shown in Figure 1 at 100% of nominal volume and at 10% of nominal volume with and without a tip change between measurements. All tips passed the recommended error set by the manufacturer except tip G, which only passed the ISO 8655 guideline. The MBP tip fitted on the tip holder but did not work with the ejector of the BioHit m200 and so the tip had to be removed manually. The results for the Finnpipette are shown in Figure 2. All the tips behaved well both without a tip change and with a tip change. Tip G had the highest systematic error and random error, but passed the calibration criteria set by the manufacturer. The results with the Gilson pipette are shown in Figure 3. All the tips performed well except tip G which failed the random error recommended by Gilson and even the ISO 8655 recommended limit at the nominal volume 100 ul. Water retention in the tip was noticed in tip G.
Discussion
Looking at the seven tips tested here, six of them (A, B, C, D, E and F) performed adequately in the tests above. Tip G should be used in a lab where precise results are not critical, such as a high school lab with limited budget.
Most pipetting will not involve water alone, but buffers and many different kinds of solutions. Solutions containing proteins or chemicals can make the liquid more or less viscous; therefore, liquid retention in the tip will reduce the accuracy and reproducibility of pipetting. A tip that shows water retention will not give the best performance.
When choosing a tip you should test it on some of the most challenging solutions used in the lab.
The new tip candidate should be fitted on all the brand of pipettes found in the lab to ensure that the ejector will reach them and eject the tips properly. In previous studies some tips fell off the tip holder of the test pipette [1].
Pricing is a big consideration in choosing a tip. Most pipette brands that sell tips will offer discounts when the lab buys a certain volume of tips. In one of the labs where I worked the pipette manufacturer offered the lab a 35% discount on the tips because of the volume of tips we used every year.
The tips used in this study are the basic tips in bulk; therefore, the least expensive option. Tip manufacturers offer their tips in individual boxes of 96 and in refill or space saver packs to refill the boxes. Most manufacturers will also have low retention tips that perform better with ‘sticky’ solutions. There are also filtered tips to avoid pipette contamination and cross contamination.
Some tips can be autoclaved for use in a sterile environment [1]. In this article the author showed that some tips failed the calibration test after being autoclaved. Testing your tip after autoclaving is a good idea to check if the tip performance has not been altered. To avoid this step tips can be purchased sterile.
Overall, there are a lot of tips out there. A little homework is necessary to ensure you have the best tip(s) for your pipette(s) that will provide accurate and reproducible results.
The author
Nicolas Gerst PhD, Co-founder and Director of Operations
Laboratory Equipment Services, LLC, Evanston, IL 60201, USA
E-mail: Ngerst.les@gmail.com
References
- Art M, Dufey V, Gast U, et al. The tip of the Iceberg: how pipette tips influence results. Eppendorf Application Note 2016; 354: 1–22 (https://www.eppendorf.com/product-media/doc/en/154106/Eppendorf_Liquid-Handling_Application-Note_354_Pipette-Tips-Tip-Iceberg-How-Pipette-Tips-Influence-Results.pdf).
- Ersoy R, Pathtech Pty Ltd. A pipette tip is a pipette tip right? Not even close. Lab+Life Scientist 2014, 15 December (https://www.labonline.com.au/content/lab-equipment/article/a-pipette-tip-is-a-pipette-tip-right-not-even-close-1022500197).
- Wenk RE, Lustgarten JA. Technology of manually operated sampler pipets. Clin Chem 1974; 20(3): 320–323.
