Glass Pasteur pipette The two types of glass that are usually found in the laboratory and in the Pasteur pipette are
borosilicate glass and
soda–lime glass. Borosilicate glass is a widely used glass for laboratory apparatus, as it can withstand chemicals and temperatures used in most laboratories. Borosilicate glass is also more economical since the glass can be fabricated easily compared to other types. Soda lime glass, although not as chemically resistant as borosilicate glass, is suitable as a material for inexpensive apparatus such as the Pasteur pipette. Traditionally, glass Pasteur pipettes were made by heating lengths of glass tubing over a flame, before drawing them apart to form a long
capillary. This capillary was further heated to bisect, producing two pipettes. Before the advent of rubber bulbs (also called
teats) to generate a vacuum, liquid was drawn up through mouth suction. Nowadays, mouth-pipetting is either strongly discouraged or forbidden. Glass Pasteur pipettes can also be used for microscale
filtration. By plugging the top (the larger aperture) with cotton or
glass wool, a solution may pass through the pipette while insoluble sediment is retained. A rubber bulb may be employed to provide additional pressure if gravity is insufficient. Glass pasteur pipettes can be used to make spotters for
thin layer chromatography after pulling it over a flame.
Plastic Pasteur pipette Plastic Pasteur pipettes, also referred to as
transfer pipettes, have their stems and bulbs in the form of a single piece made of soft plastic such as
polyethylene. The bulb portion is thinner and therefore "squeezable", while the pipette portion is thick enough to be rigid. They commonly come in 1, 2, 3, and 5 ml which comes with a specific drop size of 10, 20, 25, 35, and 50 μL. The volumes are usually marked on the stem, though the markings are rather crude and are not particularly accurate. A plastic dropper is relatively inexpensive and disposable, so they are often used to avoid cross-contamination. In a solution containing cells and/or protein, it reduces the loss of cell and/or protein that binds to glass. Some plastic pipettes include a long flexible tube that can be bent for drawing solution from small volume tubes. Plastic Pasteur pipettes are often used in
biology where most media are aqueous and solvent resistance is not important. (Most
organic solvents, such as
hexane and
acetone cannot be used in plastic Pasteur pipettes as the solvent can dissolve the plastic.) The pipettes are also hard to wash and are usually discarded with other
biohazard waste after one use. Plastic bulb pipettes are generally not precise enough to be used for exact measurements, whereas their glass counterparts can be extremely precise. ==Other usages==