Tips for field work

Molecular microbiology field work, a.k.a. amplifying within tent.

Some things you do in the lab just don’t cut it in the field. But when you get out there to do your stuff in the field, you don’t have the option of walking back to the store cupboard for another box of pipette tips, a different range pipette or one with another kind of action. The decisions have to be made before you go, and you have to live with the consequences.

Here are a few observations on the things that worked and the things that didn’t, on a recent expedition in northern Australia, remembering that molecular microbiology is not meant to be an extreme sport.

The tips themselves. Good quality, aerosol-resistant tips, pre-tested on the pipettes before departure. Poor fitting, cheap tips cause more problems than they’re worth. Poly bags or beakers of autoclaved tips don’t do the job either. The plastic boxes decent tips come in double up as a useful discard zone for used tips when you’ve gone into overdrive and used up your first box far too quickly.

aerosol-resistant tips ready for action

Size range. The best combination seems to be a collection of three sizes:

  • 10μL
  • 200μL
  • 1000μL

a good range of dispensing volumes

Every time we’ve been, we revise our estimate based on the maximum use of all reagents, and still we get caught out towards the end of the field trip. It seems the best way to go is to assume there will be some wastage, a bit of overrun and at least one change to the standard procedure. The solution seems to be to calculate the number of each size of tip then pack at least 20% more of each as shock absorbing materials around the larger items of equipment.

The pointy end. The other end of your automatic pipette needs to work well with the chosen tips, under pressure, in unfamiliar surroundings and quite often in poor light. The last issue can be addressed either by working outdoors in good, natural light, or by using a caving headlamp. To pick up easily and seal well, pipette tips need to be firm and snug on the business end of the pipette. It may seem a little obvious, but if they don’t sit well back home, they’re not likely to work well in the field. It’s not just the tips that matter here. It’s the combination of tip and pipette. The small volume ranges really need a metal front end.

sturdy, neat metal pipette end

Handy hints. A lot has been done with pipette shapes recently, with more than a passing reference to ergonomics. I guess it’s a haptic issue: the combination of size, shape, control surfaces, balance and how the moving parts change all this. My preference when working in the field is for a pipette with a bit of weight in the main body, a good tip release mechanism and a light forward/reverse pipetting action. My favorite for small volumes is the double plunger effect (200μL in the picture). It is useful to be able to hang these up above the lab bench, so a rack or rail is worth packing. If not, a few moments improvising one is worth the effort.

Waste not. It’s a given that we take our consumables waste home again when we’re finished. So there’s no excuse for failing to pack enough small plastic bags and ties to secure these when full. As small pipette tips easily pierce thin plastic, it is usually necessary to double-bag this kind of waste. Taking care with tip disposal has the added advantage of reducing the risk of molecular contamination of work surfaces.

Comments

  1. Handy hints for those who loiter within tent… http://tinyurl.com/32rw6cm

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