Proper Use of Pasteur Pipets
Pasteur pipets are traditionally one of the most abused and misunderstood items of glassware in the student labs. The goal of this section is to teach you how to properly handle Pasteur pipets.
Pipet Disposal and Reuse
The glass in a Pasteur pipet costs only 5 cents. So, why not simply use it and throw it away? First of all, it is always better to re-use something if possible, to help preserve our resources and the environment. Why have someone make another one if the one you have is perfectly okay, just a little dirty? Why add trash to the dumps if it is avoidable? Second, "dirty" glassware in a chemistry lab is not only "dirty" it is hazardous waste. The "dirt" on it is a chemical, and almost surely a hazardous chemical. Legally and morally you cannot place hazardous waste in the city dump, which is where the trash can contents end up.
We collect chemically dirty Pasteur pipets in the small white bins scattered around each lab room. Several times a week, these bins are emptied into a 55 gallon drum, which is later tagged and picked up for processing by EH&S (see the waste chemicals page). Most likely, it will be shipped to a site where it can safely be incinerated. Each pipet you put into the container burdens this expensive process.
To avoid this, you should clean and re-use your Pasteur pipets when possible. Do it immediately, before the chemical dries on the pipet and makes it impossible to clean. If the pipet has only been used for a solvent (pure hexanes,ether, ethanol, etc.), simply let it dry. If it has been used for a solution of a solid compound in a solvent, or for an aqueous acid or base, rinse it with the minimum amount necessary to get the bulk of the chemical off - use water or acetone - into the appropriate waste container, then rinse it fully under running water. Put it in your lab drawer and it will be ready for use at your next lab meeting.
If the above steps do not clean it, or if it is broken, put the Pasteur pipet in the broken glassware hazardous waste container.
Proper Pipet Technique
Pasteur pipets must be used in a vertical or near-vertical position. The bulb goes on top, the tip of the pipet is pointed down.
|Fill it like this||Hold it like this||Never do this|
Never hold a filled pipet upside down or horizontally. If you hold it this way, the liquid runs into the bulb, which means:
- The bulb is dirty and should not be used again - this means 39 cents wasted
- If it is dirty but left in use, it will quickly discolor, crack, dry up, and simply be ruined
- If a dirty bulb it is used again, any chemical left in it from the past use will mix with the new solvent, contaminating the new solvent.
- If a misused bulb is saturated with solvent and left laying about, another student might pick it up unsuspectingly gloveless, and get a hazardous chemical all over their hands
- If even a clean bulb comes into contact with any solvent, the solvent will leach out compounds naturally present in the rubber bulb, which will contaminate your solvent and hence your reaction