Pasteur pipette
Pasteur pipettes, also known as droppers or eye droppers, are used to transfer small quantities of liquids. They are usually glass tubes tapered to a narrow point, and fitted with a rubber bulb at the top. The combination of the Pasteur pipette and rubber bulb has also been referred to as a teat pipette. Pasteur pipettes come in various lengths and are sold in boxes of hundreds. They are named after the doctor Louis Pasteur
Louis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...

, who was known to have used a variant of them extensively during his research. Generally, they are considered cheap enough to be disposable, however, so long as the glass point is not chipped, the Pasteur pipette may be washed and reused indefinitely.

The name eye dropper also may refer to early models of fountain-pens, which have to be refilled with some kind of Pasteur pipette.

Plastic Pasteur pipettes

Plastic Pasteur pipettes, also referred to as transfer pipettes, have their stems and bulbs in the form of a single piece made of plastic. There are different sizes. The volumes are usually marked on the stem, though the markings are rather crude and are not particularly accurate.

Plastic Pasteur pipettes are often used in biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

 where most media are aqueous, and solvent resistance is not important. Most organic solvents, such as hexane
Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...

 and acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

, cannot be used in plastic Pasteur pipettes. They dissolve the plastic in these instruments, rendering them inadequate for many types of applications. The pipettes are also hard to wash, and are usually discarded with other biohazard
Biohazard may refer to:* Biological hazard* Biohazard , a book by Ken Alibek* Biohazard , a New York hardcore punk band** Biohazard , a self-titled album from Biohazard...

 waste after each use.

Plastic bulb pipettes are generally not precise enough to be used for exact measurements, whereas their glass counterparts can be extremely precise. The longer and thinner the tip of a glass pipette, the more exact the measurement. Usually they will be used in conjunction with a scale.

Microscale use

The constriction toward the tip of the Pasteur pipettes may be plugged with a bit of tissue paper or cotton wool to filter off solids from small amounts of liquids. The use of celite is optional. The bulb can be attached and squeezed to help viscous solutions filter more rapidly.

With a bit of skill, Pasteur pipettes may also be used for microscale column chromatography
Column chromatography
Column chromatography in chemistry is a method used to purify individual chemical compounds from mixtures of compounds. It is often used for preparative applications on scales from micrograms up to kilograms.The main advantage of column chromatography is the relatively low cost and disposability...

. With appropriately fine silica gel
Silica gel
Silica gel is a granular, vitreous, porous form of silica made synthetically from sodium silicate. Despite its name, silica gel is a solid. It is a naturally occurring mineral that is purified and processed into either granular or beaded form...

, the bulb may be squeezed for microscale flash column chromatography.

Pasteur pipettes can also be used for microscale distillations. The liquid to be distilled is placed into a small reaction tube along with a boiling chip and heated to reflux one-half to two-thirds of the way up the inside of the tube. After squeezing the bulb to expel air, a pasteur pipette is inserted into the tube just below the level of the ring of refluxing liquid (into the vapor). The vapor is then drawn into the relatively cold pipette tip, causing it to condense and accumulate inside of the pipette. By this method, enough distillate can be collected to determine a boiling point, identify a distillate, or possibly prepare derivatives.

See also

  • Laboratory glassware
    Laboratory glassware
    Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratories...

  • Pipette
    A pipette is a laboratory tool used to transport a measured volume of liquid.-Use and variations:Pipettes are commonly used in molecular biology, analytical chemistry as well as medical tests...

  • Old technique of Pasteur pipettes manufacturing video
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