PASTEUR PIPETTE: CHARACTERISTICS, TYPES AND USES - CHEMISTRY - 2024

The Pasteur pipette is a liquid transfer instrument that is not intended for quantification. However, dropper pipettes are used for the administration of medications, such as nasal and eye drops.

The Pasteur pipette, as its name implies, was the brainchild of Louis Pasteur (1822-1895), a French biologist, microbiologist, and chemist. Louis Pasteur managed to establish the principles of vaccination, bacterial fermentation, and pasteurization.

Plastic Pasteur pipettes (top) and glass (bottom). Source: Cjp24 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

The Pasteur pipette was created to solve the problems that were presented to Louis Pasteur, when carrying out the numerous tasks that he had to execute for the cultivation and inoculation of bacterial strains, thus avoiding their contamination.

In the time of Louis Pasteur, researchers had to build many of the equipment they used in their experiments. The Pasteur pipette was designed in such a way that it allowed the aspiration of the liquids of the bacterial cultures and their transfer in sterile form.

History

The invention of the Pasteur pipette is attributed to Louis Pasteur, without specifying the exact date of its creation. However, at the end of the 18th century the French chemist and pharmacist Francois Descroizilles developed the alkalimeter instrument, considered the initial precursor of the pipette.

Portrait of Louis Pasteur (Source: Paul Nadar via Wikimedia Commons)

The word pipette began to be used in the English language in 1818, before Louis Pasteur was born (1822). Pasteur invented the pipette in order to transfer liquids between containers, without the introduction of foreign elements that could contaminate the cultures of microorganisms.

Pasteur pipettes were constructed from long, thin glass tubes, the ends of which were filled with cotton to prevent the entry of germs into the tubes. The tubes were heated in the center and stretched in this area to form a very thin tube portion.

Then, the thin tube was split in the center, obtaining two pipettes. These began to be used in the laboratory, receiving various names: transfer pipettes, bulb pipettes, dropper pipettes or nipple pipettes.

Pasteur pipettes allowed the researcher to isolate pure cultures of microorganisms.

Characteristics of the Pasteur pipette

Pasteur pipette. Witia / CC BY (https://creativecommons.org/licenses/by/3.0)

Regardless of what material it is made of, the Pasteur pipette is a very simple instrument, which allows taking aliquots or small volumes of liquids without any type of graduation; Unless it is a version intended for specific purposes.

This volume is so small that when the Pasteur pipette is not used for drop measurements (such as a dropper is), it serves to transfer liquids from one site to another.

Types

Glass pipettes

Two types of glass are used in the manufacture of this type of pipettes: borosilicate glass and soda lime glass.

Pasteur pipettes are made as short pipettes and long pipettes. The short pipettes are 5.75 inches long, approximately 14.4 cm; while long pipettes are 13 inches long.

Pasteur pipettes have a diameter of 6.95 ± 0.15 mm at their wide end, and a diameter of 1.2 ± 0.15 mm at the tips. The wall of the pipettes has a thickness of 0.53 ± 0.03 mm.

Near the thick end, the pipettes have a constriction that allows a cotton plug to be placed to prevent the passage of germs into the pipettes.

The ingress and egress of liquid from the pipettes are regulated by the presence at the thick end of a bulb or nipple made of rubber or rubber material, which is squeezed or released from pressure, depending on whether it is desired to expel or aspirate liquid.

Plastic or transfer pipettes

They have a stem and bulb integrated into a single piece of soft plastic, usually polyethylene. The wall of the bulb is softer and thinner, so it can be squeezed to expel the liquid from the pipette, or to relieve pressure so that liquid aspiration occurs.

Pipettes come in volumes of 1, 2, 3, and 5 mL. Meanwhile, they are calibrated to deliver 10, 10, 25, 35 and 50 µL drops. The volumes that flow into or out of the pipettes can be visualized by the volume markings on the stem wall of the pipettes.

However, the measurement of liquid volumes in plastic Pasteur pipettes is imprecise and unreliable, and it can be said that they are reference volumes.

Applications

Sample separation

A person's blood can be centrifuged in a test tube at a specified speed and time. Once this has elapsed, the erythrocytes and leukocytes are concentrated at the bottom of the tube, while the serum or plasma remains in the supernatant.

Serum is aspirated using a Pasteur pipette and stored in vials for laboratory tests required by the patient.

Inoculation

The Pasteur pipette can be used to inoculate, in sterile form, a biological sample into a culture medium.

Chromatography mini columns

Plastic Pasteur pipettes can have the bulb partially or completely removed for use in chromatography, for example ion exchange.

The sample is allowed to penetrate through the chromatography medium, with some components of the samples adhering to the chromatography resin. These are removed from the column by washing them with a buffer supplied by the upper part of the Pasteur pipette, used in this case as a chromatography column.

The buffer (elution liquid) descends through the column by action of gravity.

Liquid purification

The Pasteur pipettes used in chromatography can be used for the purification of liquids, placing in the pipettes materials, such as glass wool, activated carbon, etc., that can trap contaminants in the liquids, thus allowing their purification.

Storage material

The material sucked into a Pasteur pipette can be stored in it, sealing the pipette tip with the flame. The liquid remaining in the pipette can then be stored in the freezer until it can be properly processed.

Medicine administration

The Pasteur pipette, acting as a dropper, can be used to administer medications through the ear, nostrils, eyes or oral cavity, as the case may be.

References

1. Wikipedia. (2020). Eye dropper. Recovered from: en.wikipedia.org
2. Alpha Laboratories. (2018). History of Pasteur Pipettes. Recovered from: pasteur-pipette.com
3. National Museum of American History. (sf). Pasteur Pipette. Recovered from: americanhistory.si.edu
4. Deltalab. (2016). Glass Pasteur pipettes. Recovered from: deltalab.es
5. EVS Translations. (2016, March 31). Pipette-word of the day. Recovered from: evs-translations.com