The proper use of Pipettes and Pipette-aids (Pipettors)

Images and some Text courtesy of this excellent, highly recommended book:

Basic Laboratory Methods for Biotechnology, Textbook and Laboratory Reference., By Lisa A. Seidman and Cynthia J.Moore, copyright 2000 Prentice-Hall, Inc.


The Procedure for Using a Serological Pipette:

Most of our work is done with sterile pipettes and if so, the operations are done aseptically.   When working with non-sterile pipettes it is a good idea to work aseptically anyway as a matter of routine in order to practice the technique.

  1. Without opening the sterile sleeve, look through the wrapper and check that the pipette is calibrated as a 'blow-out' pipette.   Also make sure that the tip is not cracked or chipped and check the wrapper hasn't been damaged in any way.
  2. Open the wrapper and remove the pipette aseptically and insert the top, wide end into a pipette-aide.
  3. Fill the pipette a bit above the capacity line desired and then slowly lower the meniscus to that capacity line.
  4. Remove the pipette from the vessel, allowing the outside of the pipette to gently touch the inner lip of the vessel to remove any adherent liquid.   Don't touch the tip of the pipette though to avoid introducing an air bubble.
  5. Aseptically move the pipette to the receiving vessel and deliver the contents.   If you are pipetting a volume between two measurement lines you will not have to 'blow-out'.   However if you are delivering the entire contents of the pipette you will have to 'blow-out' the remaining liquid in the tip with a firm puff of air from the pipette-aide.
  6. Remove the pipette aseptically and discard it into an appropriate discard container.  

Using Serological Pipettes to dispense 3.2 mL:

This is a serological pipette calibrated so that the tip includes the last milliliter.

The bands at the top indicate that this pipette is to be "blown-out."

Note that this pipette has a scale that extends above zero to expand the calibrated capacity of the pipette. Thus, this is really an 11.0 mL pipette.

The center diagram show how one would measure 3.2 mL using the 'blow-out' technique.

The diagram on the right shows how one could measure 3.2 mL using a point to point technique.

Both techniques equally accurate

Mohr pipettes are another type of pipette. Mohr pipettes are not 'blow-out' type, nor are the tips part of the measurement. Here is an example of how Mohr pipettes are used:


These types of pipettes are only used to measure using a point-to-point delivery system.

Mohr pipettes aren't commonly used in microbiology applications.