* Calibration: Pipets are calibrated to deliver a specific volume of liquid when the meniscus is at the calibration mark. This calibration assumes that a small amount of liquid will remain in the tip after dispensing. Blowing out this residual liquid will result in an inaccurate volume being delivered.
* Pipet Type:
* To-deliver (TD) pipets: These are designed to deliver the full volume indicated on the pipet when the liquid is allowed to drain freely. Blowing out the residual liquid would make the delivered volume exceed the intended amount.
* To-contain (TC) pipets: These are designed to hold a specific volume. They are not typically used for dispensing, but rather for measuring the volume of a liquid within the pipet. Blowing out would be appropriate for TC pipets since the volume delivered is not calibrated.
* Type of Liquid: Some liquids, like viscous solutions or those that tend to form bubbles, may require blowing out to ensure complete delivery. However, this should only be done if the pipet is explicitly marked as "blowout" or if the procedure specifically instructs it.
In summary:
* Unless a pipet is marked as "blowout," you should never blow out the residual liquid.
* Always follow the instructions provided in the procedure or on the pipet itself.
Let me know if you have any other questions about pipetting!
