{{Short description|Device used to transfer small quantities of liquids}} {{About|the laboratory tool|the digital tool in graphics software|Color picker|the pipette more broadly|Pipette|other uses|Dropper (disambiguation)}} [[Image:Transfer pipette.jpg|right|thumb|Plastic Pasteur pipettes]] An '''eye dropper''', also called '''Pasteur pipette''' or simply '''dropper''', is a device used to transfer small quantities of liquids.<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/dropper|title=Definition of DROPPER|website=www.merriam-webster.com|access-date=21 April 2018}}</ref> They are used in the laboratory and also to dispense small amounts of liquid medicines. A very common use is to dispense [[eye drops]] into the eye. The commonly recognized form is a [[glass tube]] tapered to a narrow point (a [[pipette]]) and fitted with a [[rubber bulb]] at the top, although many styles of both plastic and glass droppers exist. The combination of the pipette and rubber bulb has also been referred to as a teat pipette. The ''Pasteur pipette'' name is from the French scientist [[Louis Pasteur]], who used a variant of them extensively during his research. In the past, there was no equipment to transfer a chemical solution without exposing it to the external environment. The hygiene and purity of chemical compounds is necessary for the expected result of each experiment. The eye dropper, both glass and plastic types, can be sterilized and plugged with a rubber bulb at the open end of the pipette preventing any contamination from the atmosphere.<ref>{{Cite web|url=http://pasteur-pipette.com/history/history-of-pasteur-pipettes/|title=Pasteur Pipettes (transfer pipettes) – A History of glass to plastic|work=Pastette|access-date=2017-06-22|language=en-US}}</ref> Generally, they are considered cheap enough to be disposable, however, so long as the glass point is not chipped, the eye dropper may be washed and reused indefinitely.
== Overview == In laboratory use, droppers should not be used for work involving high accuracy since droppers are not designed to measure specific volume; however, it can be used to add drops of reagents. Each type of dropper is designed to produce a specific drop volume, but this is not highly precise. Before using a dropper, the tip should be carefully examined for cracks. To increase accuracy, the pipette is to be rinsed with the reagent. To use the dropper, the bulb is squeezed to expel air out of the pipette and the tip of the pipette is submerged into the solution vertically. The bulb is slowly released to draw the solution up, making sure that the solution does not overshoot into the bulb or else it may get contaminated. To dispense the reagent, the tip is held against the side of the target container at a 30 to 45 degrees angle.<ref>{{Cite news|url=https://www.biosciencetechnology.com/article/2003/01/proper-pipette-usage|title=Proper Pipette Usage|date=2003-01-14|work=Bioscience Technology|access-date=2017-06-06}}</ref>
Broken pasteur pipettes should be disposed of in an appropriate [[Sharps waste|glassware container]].<ref>{{Cite web|url=http://www.ehrs.upenn.edu/programs/environ/waste/labglassware.html|title=Laboratory Glassware Disposal {{!}} Laboratory Waste Management {{!}} Environmental {{!}} Safety Programs {{!}} EHRS|website=www.ehrs.upenn.edu|language=en|access-date=2017-06-06}}</ref>
== History == This liquid handling tool, known as the "Pasteur Pipette," was first invented by the renowned scientist [[Louis Pasteur]] in the 19th century.{{citation needed|date=January 2025}}<ref>{{cite web | last1=Sella | first1=Andrea | title=Pasteur pipette | website=Chemistry World | date=2010-03-31 | url=https://www.chemistryworld.com/opinion/pasteur-pipette/3004931.article | access-date=2026-05-07}}</ref> He is widely recognized for developing the [[Pasteurization|pasteurization process]], and the pipettes were named in his honor.<ref>{{Cite web |title=Pasteur Pipette Archives |url=https://www.glasscolabs.com/product-category/laboratory-glassware/disposable-glassware/pasteur-pipette/#:~:text=The%20pasteur%20pipettes%20are%20commonly,the%20top%20of%20the%20pipette. |access-date=2024-09-04 |website=Glasscolabs |language=en-US}}</ref>
== Types == ===Glass Pasteur pipette=== [[File:S 2695170.jpg|thumb|right|Glass Pasteur pipettes]]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.<ref>{{cite web|url=http://www1.udel.edu/chem/GlassShop/PhysicalProperties.htm|title=Physical Properties|website=www1.udel.edu|access-date=21 April 2018|archive-url=https://web.archive.org/web/20171205135450/http://www1.udel.edu/chem/GlassShop/PhysicalProperties.htm|archive-date=5 December 2017|url-status=dead}}</ref>{{Inconsistent|date=January 2026}}
Traditionally, glass Pasteur pipettes were made by heating lengths of glass tubing over a flame, before drawing them apart to form a long [[Capillary action|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.<ref>{{Cite web |title=Pasteur Pipette |url=https://americanhistory.si.edu/collections/object/nmah_1458876 |access-date=2026-01-10 |website=National Museum of American History |language=en}}</ref><ref>{{Cite web |title=Chemistry Teaching Labs - Using a Pasteur pipette |url=https://chemtl.york.ac.uk/techniques/basic-techniques/pipettes/using-a-pasteur-pipette |access-date=2026-01-10 |website=chemtl.york.ac.uk |language=en-US}}</ref> Nowadays, mouth-pipetting is either strongly discouraged or forbidden.<ref>{{Cite web |title=1910.1450 App A - National Research Council Recommendations Concerning Chemical Hygiene in Laboratories (Non-Mandatory) {{!}} Occupational Safety and Health Administration |url=https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1450AppA?utm |access-date=2026-01-10 |website=www.osha.gov}}</ref><ref>{{Cite web |title=DSpace |url=https://iris.who.int/bitstream/handle/10665/42981/9241546506_eng.pdf?utm |access-date=2026-01-10 |website=iris.who.int}}</ref><ref>'''Centers for Disease Control and Prevention & National Institutes of Health.''' ''Biosafety in Microbiological and Biomedical Laboratories (BMBL), 6th Edition.''</ref>
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.<ref>{{Cite web |title=Chemistry Teaching Labs - Microscale Filtration |url=https://chemtl.york.ac.uk/techniques/reaction-techniques/filtration/micro |access-date=2026-01-10 |website=chemtl.york.ac.uk |language=en-US}}</ref>
Glass pasteur pipettes can be used to make spotters for [[Thin-layer chromatography|thin layer chromatography]] after pulling it over a flame.<ref>{{Cite journal |last=Cai |first=Li |date=2014 |title=Thin Layer Chromatography |url=https://currentprotocols.onlinelibrary.wiley.com/doi/10.1002/9780470089941.et0603s08 |journal=Current Protocols in Essential Laboratory Techniques |language=en |volume=8 |issue=1 |doi=10.1002/9780470089941.et0603s08 |issn=1948-3430|url-access=subscription }}</ref>
===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.<ref>{{Cite web|url=http://www.ajoshabioteknik.in/laboratory-pipette.html#pasteur-pipettes|title=Pasteur Pipette - Pasteur Pipettes Manufacturer from Mumbai|website=www.ajoshabioteknik.in|access-date=2017-05-30}}</ref> The volumes are usually marked on the stem, though the markings are rather crude and are not particularly accurate.<ref>{{Cite news|url=https://greenbioresearch.com/choose-pasteur-pipettes-pasteur-liquid-transfer-pipette-eye-droppers/|title=How to Choose Pasteur Pipettes, Pasteur Liquid Transfer Pipette, Eye Droppers|date=2017-01-02|work=Green BioResearch LLC|access-date=2017-05-30|language=en-US}}</ref>
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.<ref>{{Cite web|url=http://www.argos-tech.com/plastic-pasteur-pipettes_2.html|title=Plastic Serological Pipettes|date=2017|website=Argos Technologies}}</ref>
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.<ref name=":0">{{Cite book|title=Essentials of Clinical Laboratory Science|url=https://archive.org/details/essentialsclinic00ridl|url-access=limited|last=Ridley|first=John|publisher=Cengage Learning|year=2010|isbn=9781435448148|pages=[https://archive.org/details/essentialsclinic00ridl/page/n232 199]}}</ref>
Plastic bulb pipettes are generally not precise enough to be used for exact measurements, whereas their glass counterparts can be extremely precise.<ref name=":0" />
==Other usages== ===Microscale column chromatography=== [[File:Column Chromatography 01.jpg|thumb|upright|Column chromatography constructed using plastic Pasteur pipette]] 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 bulb can be attached and squeezed to help viscous solutions filter more rapidly.<ref>{{Cite web|url=http://www.csudh.edu/oliver/demos/pipetuse/pipetuse.htm|title=Helpful Hints on the Use of a Volumetric Pipet|last=Seely|first=Oliver|website=www.csudh.edu|access-date=2017-06-13|archive-date=2013-06-30|archive-url=https://web.archive.org/web/20130630142910/http://www.csudh.edu/oliver/demos/pipetuse/pipetuse.htm|url-status=dead}}</ref>
With a bit of skill, Pasteur pipettes may also be used for microscale [[column chromatography]]. With appropriately fine [[silica gel]], the bulb may be squeezed for microscale [[flash column chromatography]].<ref>[[University of Colorado at Boulder]], [http://orgchem.colorado.edu/hndbksupport/colchrom/colchromprocmicroflash.html Procedure for Microscale Flash Column Chromatography] {{Webarchive|url=https://web.archive.org/web/20130524011830/http://orgchem.colorado.edu/hndbksupport/colchrom/colchromprocmicroflash.html |date=2013-05-24 }}. Accessed 1 Nov 2006.</ref>
===Microscale distillation=== Pasteur pipettes can also be used for microscale [[distillation]].<ref>{{Cite web|url=http://www.chemistry.mcmaster.ca/~chem2o6/labmanual/microscale/complete.html|title=Microscale Techniques - Complete Manual|website=www.chemistry.mcmaster.ca|access-date=2017-06-13}}</ref> 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.
===Microscale liquid storage=== Heat can be applied to the tip of a plastic Pasteur pipette to seal the solution and create a liquid-tight storage.<ref>{{Cite web|url=http://www.sigmaaldrich.com/catalog/product/sigma/z354368?lang=en®ion=TH&cm_sp=Insite-_-prodRecCold_xviews-_-prodRecCold10-9|title=Transfer pipette, polyethylene Z354368|website=Sigma-Aldrich|language=en|access-date=2017-05-30}}</ref>
== Additional images == <gallery> File:Einwegpipetten.jpg|Plastic Pasteur pipette File:Pasteur pipette.jpg|Pipette bulb File:Glass pasteur pipette.jpg|Pipette glass tube File:Pp pasteur pipette1.jpg|Pipette container </gallery>
==See also== * [[Pipette]]
==References== <references/>
{{laboratory equipment}}
[[Category:Laboratory glassware]]