Repeater pipettes are the energizer bunnies of the pipetting world - pull up liquid once and they just keep on going (dispensing a set amount of liquid over and over)! So your experiments can keep on going - without your thumbs falling off! They’re great for doing things like: making aliquots (splitting up a large volume into a bunch of smaller portions (great for avoiding freeze-thaws, reducing stock contamination, etc.); doing lots of mini preps or other spin column purifications in parallel; setting up crystallography screens, etc. But they can be a bit finicky, so here are some tips for using them.
Instead of normal pipets where you suck up (aspirate) a set amount of liquid and then push out (dispense) that same amount of liquid - and then have to re-aspirate if you want to dispense again, with a repeater pipet, you pull up more liquid than you need and have it dispense a set amount every time you push down. What that amount is will be restricted by the tip size & their “step sizes” (e.g. you can adjust by 1μL increments with a 100 μL tip but only 2μL increments with a 200 μL tip and only 100 μL with a 10 mL tip). Basically, the smaller the tip, the smaller the portions you can make and the more control you have over the exact size of those portions.
No matter what size, the basic operating principles are the same:
- snap on the tip (make sure it’s straight) - listen for the click
- push down the bottom lever - listen for another click
- use the dial to set the volume you want to dispense each time - it will tell you how many times you can dispense that amount if you fill the tip
- stick the tip in your liquid (note that some of the tips are pretty wide-diameter-ed, so you might need to use a 50 mL conical instead of a 15 mL one so you can reach the bottom)
- pull up that bottom lever to suck up enough liquid to dispense the number of samples you want to dispense
- be careful not to introduce air!
- push down the top lever back into the tube to get “excess” out - don’t use that first dispensed bit - it won’t be accurate
- now push down the top lever over and over and over and over… each time dispensing the correct amount until you get the the end and there’s not a full amount left
- push the bottom lever down to push that out into the original tube or waste container OR, suck up more (again, careful not to introduce bubbles)
- eject the tip by pushing down the bottom lever and the top lever at the same time
a couple tips:
- check the tip when you’re dispensing to make sure there aren’t any bubbles in there that would mess up the volume
- when dispensing small volumes make sure stuff is actually coming out - and going into your dispenser (pipetting onto wall of tube helps)
- be careful not to splash - especially can be an issue when doing ethanol-containing washes in mini preps - dispense with the tip held inside the tube and don’t rush (you’re still saving time over a normal pipet, don’t worry!)
Another time-saving pipet is the multichannel pipet - this is great when have to pipette into multi-well plates. We have 8-channel and 12-channel ones in multiple volumes.  These are basically just a normal pipet with lots of tips stuck together. So you still only dispense once per aspiration, but you can do it into multiple wells, tubes, etc. at the same time. But your sample has to be “spread out” (in tubes or a reagent reservoir that’s basically just a little dish thing), so you have to make more extra than with the repeater pipet. But with the repeater you do still need to make extra. You should always make extra to account for liquid loss on the tips, etc. but you should make extra extra when using the repeater and extra extra extra when using the multichannel!
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more time-saving tips when working with lots of samples: bit.ly/mastermixesmultichannels
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more about all sorts of things: #365DaysOfScience All (with topics listed) 👉 bit.ly/2OllAB0 or search blog: thebumblingbiochemist.com