Pipetting game: two stops, no bubbles
Three wells, three volumes and a pipette whose plunger stops twice. Push, draw up, find the well and empty the tip without wasting a drop.
- 01 Set the volume
- 02 Draw up
- 03 Find the well
- 04 Push it out
I use a transfection mix to help DNA enter the cells. You'll see some of my cells under the microscope at 14:20.
What this simulates
What you do
Each round gives you a volume and a well: 50 µL into B3, then 120 µL into C5, then 25 µL into A2. You dial the pipette to the volume (the dial runs from 20 to 200 µL). Then you drag the plunger down to the first stop, or use the arrow keys, and let it up slowly to draw the liquid in. Next you click the right well on the plate and push past the first stop to the second, then let the plunger up.
Each round is scored out of 100. You lose points for pulling in a bubble by letting the plunger up too fast, for going to the wrong well, for pressing past the first stop before drawing up, and for leaving a drop in the tip. A clean round scores 100.
The real technique
Many bench pipettes have a plunger with two stops. The first stop is the one that matches the volume you have set: you push down to it before drawing up. Letting the plunger rise slowly lifts the liquid into the tip smoothly. Letting it go too quickly can pull in air, which gives you a bubble and the wrong volume.
The second stop is for dispensing. Pushing all the way to it empties the tip, including the last drop. The wells are labelled by row and column, as on a plate, so you also have to check which well you are over before you push.
What you learn
Why the order of the plunger matters, why the way up is slow, and why small volumes are easy to get wrong. A few microlitres in the wrong place, or with a bubble in it, changes an experiment, so the care you practise here carries over to real plates.