- automatic pipettes
- E. coli
- environmental chamber
- Escherichia coli
- growth curves
- heated chamber
- M9 minimal medium
- mini centrifuges
- time-lapse microscopy
25 October 2019
I have been quite ignorant when it comes to automatic pipettes. From my very fist volunteer lab practical I was exposed to the Pipetman range from Gilson, and they have simply not let me down. I have used these pipettes all through my PhD and my postdoc studies and these pipettes simply work. I have inherited some pipettes that are now approximatley 25 years old and with occasional calibration these are as accurate as the new models we have equipped the lab with.
When it came to buying more pipettes when I set up my own lab I had very little funds to begin with and bought a relatively inexpensive set of Finnpettes F2 from ThermoFisher Scientific. In my personal opinion they are slightly too thin for a comfortable grip, they are also slightly too light to get the tips to a good fit without much strain and they feel cheap. However, in the past 10 years they have worked fine, even though suffering some student abuse on occasion. Again with occasional calibration they are pretty much as accurate as they were at the beginning.
One detail that students find very confusing is the volume indicator on the Gilson models. Even though quickly to learn, students find the 3 digits very confusing. They simply struggle that for the P1000 a setting of 050 means something different than for the P200, and they never notice the red colour for the P1000 and the p20 and P10, indicating the larger volume and the decimal point, respectively. The Finnpettes F2 series is slightly better in this regard. The P1000 equivalent comes with 4 digits, which appears to be much easier to grasp by students, and they feature a decimal point.
The German brand IKA has now started to make their own pipette range and as we needed another set I have bought the equivalent of the P20, P200 and P1000. After some work with them I was quite surprised about what works well and what does not work so well. In terms of weight they are slightly lighter than the Gilson pipettes. This is only ~15 g, but it still makes a difference when picking up tips, a fact that might also be influenced by the shape of the sealing end of the shaft. Nevertheless, picking up tips with a Gilson can be done with very little force. The weight of the pipette itself is enough to firmly push a tip onto the end. At least for me this does not work quite as well with the IKA Pettes. They always require some extra force, otherwise the tip is in danger of falling off, even though this is better than with the Finnpettes F2, which are even lighter. For my personal use IKA certainly got the diameter right and I find the pipettes comfortable to hold. The operating mechanism is smooth and light, making pipetting quite enjoyable. However, there are some additional details that do not work as well. For example, when used with Starlab tips, which is our preferred tip provider, the P1000 is about 1.5 mm short of reaching the bottom of conventional 15 ml Falcon tubes. The remaining volume is very small, but still, why not make the shaft 2 mm longer and avoid the problem alltogether?
When it comes to the volume indicator the IKA pettes certainly are student-friendly, as they all feature a 4-digit display. However, in practise this actually does not work overly well, because it increases the resistance when changing volumes. There is no point for the P20 equivalent to have to digits after the decimal point. The single decimal point of the P200 might be more useful on occasion, but the way Gilson has done this with an extra graduation on the turning wheel works perfectly well and also conveys in some way the limited accuracy. I find changing volume with the IKA Pettes far more tiresome than with Gilsons and the Finnpettes F2 set. The IKA Pette volume setting can be locked, which on paper is a nice feature for student work. However, I certainly have not needed this feature when actively working at the bench. When doing very repetitive work the Gilsons might change very slightly, but that can be easily adjusted.
The IKA Pettes can be user calibrated, which might be useful especially when working with students. However, I would not really want to do this for sensitive lab work. The high accuracy and durability of the Gilson range clearly indicates that if for some reason the volume is out then something is slightly (or not so slightly) wrong with the mechanism and the pipette needs servicing and calibrating. As the Finnpettes F2 they can be autoclaved, which can be useful. However, again, if they are contaminated by culture droplets I would want to the give the shaft a throrough clean anyway and we use autoclaving rarely for our purposes, as E. coli is very efficiently killed by ethanol. Obviously working with other organisms will be another story.
Overall I find the differences highlighted all to be relatively minor. All the pipettes I have used in recent years do their job, so it comes down to the finer details when distinguishing between the various models. For good PhD students and especially postdoctoral researchers I would without hesitation buy Gilson pipettes, as they are accurate, have a good weight and an easy to use volume indicator that is not too strenuous. However, for student work I rather like having both the Finpettes F2 set and the IKA Pettes in the lab.
The IKA Pettes were directly bought from IKA, while all Gilson pipettes were purchased from SLS. The Finpettes F2 series was directly purchased from Fisher Scientific.