Stuff that occurs to me

All of my 'how to' posts are tagged here. The most popular posts are about blocking and private accounts on Twitter, also the science communication jobs list. None of the science or medical information I might post to this blog should be taken as medical advice (I'm not medically trained).

Think of this blog as a sort of nursery for my half-baked ideas hence 'stuff that occurs to me'.

Contact: @JoBrodie Email: jo DOT brodie AT gmx DOT com

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Wednesday, 5 December 2012

How to pipette properly

This is for the benefit of anyone making TV series or films that feature the transfer of small amounts of liquid from one place to another via pipette, in a laboratory setting - let's get it right. Or at least a bit right-er.

OK it's probably a bit rich of me to tell anyone how to pipette properly as it's been almost ten years since I stepped foot inside a lab, and to be fair most of the stuff I was handling wasn't amenable to plasticware (I was doing lipid science which requires some chemicals that tend to destroy plastic. The destruction of the plastic is less of a problem than the fact that contact between the chemical and the plastic can cause stuff that's in the plastic to 'leach out', wrecking the sample. Glass all the way.)

1. Gloves are there to protect you from the chemicals and whatnot, but importantly they're also there to protect whatever you're handling from you (from your sweat, dust and other stuff on your skin) so when wearing gloves don't fiddle with your hair or face. In some cases you might want to avoid picking up the phone or opening the door with a gloved hand, it does depend though. Ten years on and I still open doors with my foot in preference, where possible.

2. No 'skooshing' of the liquid from the pipette into the test-tube or wherever it's being placed. While this will certainly encourage mixing, which you often want, if you whoosh it in too fast you can lose some of it. If you skoosh it into a test-tube that already contains some liquid then you can end up jettisoning some of that liquid too - so you end up with the wrong amounts of everything. Or, you might form aerosols (tiny breathable liquid particles which you probably don't want). Not crucial if you're making orange squash but not so good in science.

Generally, you should angle the test-tube and touch the end of the disposable pipette tip against the lower side and depress the plunger gently. The liquid will then trickle down gracefully. If you want to mix it with another liquid (or dissolve something in the tube) you can suck up a bit of the slightly mixed liquid and repeat a few times (squidge it up and down a bit), or hold firmly (in your hand) but lightly against one of those vortex mixers).

I was once asked, by a new student in the lab, what the vortex mixer was for and I helpfully explained that you could put an Eppendorf (microcentrifuge) tube on it and it would mix it nicely for you. How we laughed when he took it a bit literally and he placed it on the mixer - without holding onto it - and it pinged off across the lab.

Next week: How to make fatty acid methyl esters. Kidding :)



2 comments:

  1. Very good advice! You might like our micropipetting video, plenty of advice about what to do and not do! http://www2.le.ac.uk/departments/genetics/vgec/schoolscolleges/topics/recombinanttechniques/micropipette-whole

    ReplyDelete
    Replies
    1. Thanks Jo - I approve of the level of detail in this video :)

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