How to use a pipette: Pre- and post-dispense (video)
How to use a pipette: Pre- and post-dispense
Welcome back, electronic pipettes are incredibly useful tools in the lab and a large part of that, is their ability to repeat the spend. That is multiple altoids after one aspiration. This really increases productivity. You can pipette faster with less errors.
However, to achieve the best results, when performing to repeat the spend, follow the simple rule - always discard the first and the last dispense. When the electronic pipette is finished aspirating the liquid and you want to repeat dispense, the mechanics inside the pipette need to change direction from aspiration to dispense.
This could result in the first dispense being too low in volume, to eliminate this effect it's recommended to discard the first dispense. Often back into the source vessel. This is typically three to five percent of the pipette's full volume and is sometimes called the pre-dispense. All dispenses after that can be used, but remember that no pipette is a hundred percent accurate. Each dispense might be slightly off the target volume and these errors accumulate.
Eventually we get to the last dispense and the amount of liquid in the tip is likely not what you think it is. To eliminate this problem, simply discard the last suspend. Again this is typically three to five percent of the piper's full volume and is sometimes called the posters pen. With the free and the post dispense discarded, you really see a big improvement in your overall results.