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A pipette (sometimes spelled as pipett) is a laboratory tool commonly used in
chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
,
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
and
medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pract ...
to transport a measured volume of liquid, often as a
media dispenser A media dispenser or a culture media dispenser is a device for repeatedly delivering small fixed volumes (typically between 1 ml and 50 ml) of liquid such as a laboratory growth medium like molten agar or caustic or volatile solvents li ...
. Pipettes come in several designs for various purposes with differing levels of
accuracy and precision Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements ( observations or readings) are to their ''true value'', while ''precision'' is how close the measurements are to each oth ...
, from single piece glass pipettes to more complex adjustable or electronic pipettes. Many pipette types work by creating a
partial vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...
above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid. Measurement accuracy varies greatly depending on the instrument.


History

The first simple pipettes were made in glass, such as
Pasteur pipette An eye dropper, also called Pasteur pipette or simply dropper, is a device used to transfer small quantities of liquids. They are used in the laboratory and also to dispense small amounts of liquid medicines. A very common use was to dispense e ...
s. Large pipettes continue to be made in glass; others are made in squeezable plastic for situations where an exact volume is not required. The first micropipette was patented in 1957 by Dr
Heinrich Schnitger Heinrich Schnitger (10 May 1925 in Lemgo - 27 August 1964 in Upper Bavaria) was a German physician. He is considered the inventor of the piston stroke Micropipette, a laboratory device for dispensing small amounts of liquid. Life Heinrich Schnitg ...
(
Marburg Marburg ( or ) is a university town in the German federal state (''Bundesland'') of Hesse, capital of the Marburg-Biedenkopf district (''Landkreis''). The town area spreads along the valley of the river Lahn and has a population of approximate ...
, Germany). The founder of the company Eppendorf, Dr. Heinrich Netheler, inherited the rights and started the commercial production of micropipettes in 1961. The adjustable micropipette is a Wisconsin invention developed through interactions among several people, primarily inventor Warren Gilson and Henry Lardy, a professor of biochemistry at the
University of Wisconsin–Madison A university () is an educational institution, institution of higher education, higher (or Tertiary education, tertiary) education and research which awards academic degrees in several Discipline (academia), academic disciplines. Universities ty ...
.


Nomenclature

Although specific descriptive names exist for each type of pipette, in practice any type of pipette will merely be referred to as a "pipette" and the desired device will be obvious from context. Sometimes, pipettes that dispense between 1 and 1000 
μl The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). ...
are distinguished as micropipettes, while macropipettes dispense greater volumes.


Common pipettes


Air displacement micropipettes

Air displacement micropipettes are a type of adjustable micropipette that deliver a measured volume of liquid; depending on size, it could be between about 0.1  µl to 1,000 µl (1 ml). These pipettes require disposable tips that come in contact with the fluid. The four standard sizes of micropipettes correspond to four different disposable tip colors: These pipettes operate by
piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...
-driven
air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...
displacement. A vacuum is generated by the vertical travel of a metal or ceramic piston within an airtight sleeve. As the piston moves upward, driven by the depression of the plunger, a vacuum is created in the space left vacant by the piston. The liquid around the tip moves into this vacuum (along with the air in the tip) and can then be transported and released as necessary. These pipettes are capable of being very precise and accurate. However, since they rely on air displacement, they are subject to inaccuracies caused by the changing environment, particularly temperature and user technique. For these reasons, this equipment must be carefully maintained and calibrated, and users must be trained to exercise correct and consistent technique. The micropipette was invented and patented in 1960 by Dr.
Heinrich Schnitger Heinrich Schnitger (10 May 1925 in Lemgo - 27 August 1964 in Upper Bavaria) was a German physician. He is considered the inventor of the piston stroke Micropipette, a laboratory device for dispensing small amounts of liquid. Life Heinrich Schnitg ...
in
Marburg Marburg ( or ) is a university town in the German federal state (''Bundesland'') of Hesse, capital of the Marburg-Biedenkopf district (''Landkreis''). The town area spreads along the valley of the river Lahn and has a population of approximate ...
, Germany. Afterwards, the co-founder of the biotechnology company Eppendorf, Dr. Heinrich Netheler, inherited the rights and initiated the global and general use of micropipettes in labs. In 1972, the adjustable micropipette was invented at the University of Wisconsin-Madison by several people, primarily Warren Gilson and Henry Lardy. Types of air displacement pipettes include: * adjustable or fixed * volume handled * Single-channel, multi-channel or repeater * conical tips or cylindrical tips * standard or locking * manual or electronic * manufacturer Irrespective of brand or expense of pipette, every micropipette manufacturer recommends checking the calibration at least every six months, if used regularly. Companies in the drug or food industries are required to calibrate their pipettes quarterly (every three months). Schools which are conducting
chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
classes can have this process annually. Those studying forensics and research where a great deal of testing is commonplace will perform monthly calibrations.


Electronic pipette

To minimize the possible development of
musculoskeletal disorders Musculoskeletal disorders (MSDs) are injuries or pain in the human musculoskeletal system, including the joints, ligaments, muscles, nerves, tendons, and structures that support limbs, neck and back. MSDs can arise from a sudden exertion (e.g., li ...
due to repetitive pipetting,
electronic pipettes Piston-driven air displacement pipettes are a type of micropipette, which are tools to handle volumes of liquid in the microliter scale. They are more commonly used in biology and biochemistry, and less commonly in chemistry; the equipment is susc ...
commonly replace the mechanical version.


Positive displacement pipette

These are similar to air displacement pipettes, but are less commonly used and are used to avoid contamination and for volatile or viscous substances at small volumes, such as DNA. The major difference is that the disposable tip is a microsyringe (plastic), composed of a capillary and a piston (movable inner part) which directly displaces the liquid. File:Positive displacement pipette.jpg, Positive displacement pipette File:Pos pipette showing grappler.jpg, The
chuck Chuck is a masculine given name or a nickname for Charles or Charlie. It may refer to: People Arts and entertainment * Chuck Alaimo, American saxophonist, leader of the Chuck Alaimo Quartet * Chuck Barris (1929–2017), American TV producer * C ...
which will be used to move the plunger File:early pipette.jpg, An early pipette


Volumetric pipettes

Volumetric pipettes A volumetric pipette, bulb pipette, or belly pipette allows extremely accurate measurement (to four significant figures) of the volume of a solution. It is calibrated to deliver accurately a fixed volume of liquid. These pipettes have a large bu ...
or
bulb pipette A volumetric pipette, bulb pipette, or belly pipette allows extremely accurate measurement (to four significant figures) of the volume of a solution. It is calibrated to deliver accurately a fixed volume of liquid. These pipettes have a large bu ...
allow the user to measure a volume of solution extremely precisely (precision of four significant figures). These pipettes have a large bulb with a long narrow portion above with a single graduation mark as it is calibrated for a single volume (like a
volumetric flask A volumetric flask (measuring flask or graduated flask) is a piece of laboratory apparatus, a type of laboratory flask, calibrated to contain a precise volume at a certain temperature. Volumetric flasks are used for precise dilutions and prepar ...
). Typical volumes are 20, 50, and 100 mL. Volumetric pipettes are commonly used to make laboratory solutions from a base stock as well as prepare solutions for
titration Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte (a substance to be analyzed). A reagent, termed the ''titrant'' ...
.


Graduated pipettes

Graduated pipettes A graduated pipette is a pipette with its volume, in increments, marked along the tube. It is used to accurately measure and transfer a volume of liquid from one container to another. It is made from plastic or glass tubes and has a tapered tip. ...
are a type of macropipette consisting of a long tube with a series of graduations, as on a
graduated cylinder A graduated cylinder, also known as a measuring cylinder or mixing cylinder, is a common piece of laboratory equipment used to measure the volume of a liquid. It has a narrow cylindrical shape. Each marked line on the graduated cylinder represent ...
or
burette A burette is a graduated glass tube with a tap at one end, for delivering known volumes of a liquid, especially in Titration, titrations. It is a long, graduated glass tube, with a stopcock at its lower end and a tapered capillary tube at the stop ...
, to indicate different calibrated volumes. They also require a source of vacuum; in the early days of chemistry and biology, the mouth was used. The safety regulations included the statement: "Never pipette by mouth KCN, NH3, strong acids, bases and mercury salts". Some pipettes were manufactured with two bubbles between the mouth piece and the solution level line, to protect the chemist from accidental swallowing of the solution. File:"Pfc. Johnnie Mae Welton, Negro WAC, laboratory technician trainee, conducts an experiment in the serology laboratory sf - NARA - 531360.tif, A person pipetting by mouth, now considered an unsafe practice File:2Pipettierhilfen.jpg, A manual propipetter adjusted by turning the wheel with the thumb File:Pipetteerballon.png, A manual propipetter adjusted by squeezing the valves marked E and S File:Pipettier-Hilfe.jpg, An automatic propipetter adjusted by pressing the button and toggling the switch File:Motorized pipetter blue.jpg, An automatic propipetter adjusted by pulling and releasing the triggers


Pasteur pipette

Pasteur pipette An eye dropper, also called Pasteur pipette or simply dropper, is a device used to transfer small quantities of liquids. They are used in the laboratory and also to dispense small amounts of liquid medicines. A very common use was to dispense e ...
s are plastic or glass pipettes used to transfer small amounts of liquids, but are not graduated or calibrated for any particular volume. The bulb is separate from the pipette body. Pasteur pipettes are also called
teat A teat is the projection from the mammary glands of mammals from which milk flows or is ejected for the purpose of feeding young. In many mammals the teat projects from the udder. The number of teats varies by mammalian species and often corr ...
pipettes, droppers, eye droppers and chemical droppers.


Transfer pipettes

Transfer pipette An eye dropper, also called Pasteur pipette or simply dropper, is a device used to transfer small quantities of liquids. They are used in the laboratory and also to dispense small amounts of liquid medicines. A very common use was to dispense e ...
s, also known as Beral pipettes, are similar to Pasteur pipettes but are made from a single piece of plastic and their bulb can serve as the liquid-holding chamber.


Specialized pipettes


Pipetting syringe

Pipetting syringes are hand-held devices that combine the functions of volumetric (bulb) pipettes, graduated pipettes, and
burette A burette is a graduated glass tube with a tap at one end, for delivering known volumes of a liquid, especially in Titration, titrations. It is a long, graduated glass tube, with a stopcock at its lower end and a tapered capillary tube at the stop ...
s. They are calibrated to
ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...
volumetric A grade standards. A glass or plastic pipette tube is used with a thumb-operated piston and
PTFE Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemour ...
seal which slides within the pipette in a positive displacement operation. Such a device can be used on a wide variety of fluids (aqueous, viscous, and volatile fluids; hydrocarbons; essential oils; and mixtures) in volumes between 0.5 mL and 25 mL. This arrangement provides improvements in precision, handling safety, reliability, economy, and versatility. No disposable tips or pipetting aids are needed with the pipetting syringe.


Van Slyke pipette

A graduated pipette commonly used in
medical technology Health technology is defined by the World Health Organization as the "application of organized knowledge and skills in the form of devices, medicines, vaccines, procedures, and systems developed to solve a health problem and improve quality of liv ...
with serologic pipettes for volumetric analysis. Invented by
Donald Dexter Van Slyke Donald Dexter Van Slyke (March 29, 1883 – May 4, 1971) was a Dutch American biochemist. His achievements included the publication of 317 journal articles and 5 books, as well as numerous awards, among them the National Medal of Science and t ...
.


Ostwald–Folin pipette

A special pipette used in measuring viscous fluid such as whole blood. Common in medical technology laboratory setups together with other pipettes. Invented by
Friedrich Wilhelm Ostwald Friedrich Wilhelm Ostwald (; 4 April 1932) was a Baltic German chemist and philosopher. Ostwald is credited with being one of the founders of the field of physical chemistry, with Jacobus Henricus van 't Hoff, Walther Nernst, and Svante Arrhe ...
, a Baltic German Chemist and later refined by
Otto Folin Otto Knut Olof Folin (April 4, 1867 – October 25, 1934) was a Swedish-born American chemist who is best known for his groundbreaking work at Harvard University on practical micromethods for the determination of the constituents of protein-f ...
, an American chemist.


Glass micropipette

These are used to physically interact with microscopic samples, such as in the procedures of
microinjection Microinjection is the use of a glass micropipette to inject a liquid substance at a microscopic or borderline macroscopic level. The target is often a living cell but may also include intercellular space. Microinjection is a simple mechanical pro ...
and
patch clamp The patch clamp technique is a laboratory technique in electrophysiology used to study ionic currents in individual isolated living cells, tissue sections, or patches of cell membrane. The technique is especially useful in the study of excitabl ...
ing. Most micropipettes are made of
borosilicate Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...
,
aluminosilicate Aluminosilicate minerals ( IMA symbol: Als) are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals. Andalusite, kyanite, and sillimanite are naturall ...
or
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
with many types and sizes of glass tubing being available. Each of these compositions has unique properties which will determine suitable applications. Glass micropipettes are fabricated in a micropipette puller and are typically used in a
micromanipulator A micromanipulator is a device which is used to physically interact with a sample under a microscope, where a level of precision of movement is necessary that cannot be achieved by the unaided human hand. It may typically consist of an input joysti ...
.


Microfluidic pipette

A recent introduction into the micropipette field integrates the versatility of
microfluidics Microfluidics refers to the behavior, precise control, and manipulation of fluids that are geometrically constrained to a small scale (typically sub-millimeter) at which surface forces dominate volumetric forces. It is a multidisciplinary field tha ...
into a freely positionable pipette platform. At the tip of the device a localized flow zone is created, allowing for constant control of the nanoliter environment, directly in front of the pipette. The pipettes are made from
polydimethylsiloxane Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, as its ...
(PDMS) which is formed using reactive injection molding. Interfacing of these pipettes using pneumatics enables multiple solutions to be loaded and switched on demand, with solution exchange times of 100ms.
Invented by Alar Ainla, currently situated in the Biophysical Technology Lab at
Chalmers University of Technology Chalmers University of Technology ( sv, Chalmers tekniska högskola, often shortened to Chalmers) is a Swedish university located in Gothenburg that conducts research and education in technology and natural sciences at a high international leve ...
in Sweden.


Extremely low volume pipettes

A zeptoliter pipette has been developed at
Brookhaven National Laboratory Brookhaven National Laboratory (BNL) is a United States Department of Energy national laboratory located in Upton, Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base and Japanese internment c ...
. The pipette is made of a carbon shell, within which is an alloy of gold-germanium. The pipette was used to learn about how
crystallization Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposi ...
takes place.


Pipette aids

A variety of devices have been developed for safer, easier, and more efficient pipetting. For example, a motorized pipette controller can aid liquid aspiration or dispensing using volumetric pipettes or graduated pipettes; a tablet can interact in real-time with the pipette and guide a user through a protocol; and a pipette station can help to control the pipette tip immersion depth and improve ergonomics.


Robots

Pipette robots are capable of manipulating the pipettes as humans would do.


Calibration

Pipette recalibration is an important consideration in laboratories using these devices. It is the act of determining the accuracy of a measuring device by comparison with NIST traceable reference standards. Pipette calibration is essential to ensure that the instrument is working according to expectations and as per the defined regimes or work protocols. Pipette calibration is considered to be a complex affair because it includes many elements of calibration procedure and several calibration protocol options as well as makes and models of pipettes to consider.


Posture and injuries

Proper pipetting posture is the most important element in establishing good ergonomic work practices. During repetitive tasks such as pipetting, maintaining body positions that provide a maximum of strength with the least amount of muscular stress is important to minimize the risk of injury. A number of common pipetting techniques have been identified as potentially hazardous due to biomechanical stress factors. Recommendations for corrective pipetting actions, made by various US governmental agencies and ergonomics experts, are presented below. ;Winged elbow pipetting :Technique: elevated, “winged elbow”. The average human arm weighs approximately 6% of the total body weight. Holding a pipette with the elbow extended (winged elbow) in a static position places the weight of the arm onto the neck and shoulder muscles and reduces blood flow, thereby causing stress and fatigue. Muscle strength is also substantially reduced as arm flexion is increased. :Corrective action: Position elbows as close to the body as possible, with arms and wrists extended in straight, neutral positions (handshake posture). Keep work items within easy reach to limit extension and elevation of arm. Arm/hand elevation should not exceed 12” from the worksurface. ;Over rotated arm pipetting :Technique: Over-rotated forearm and wrist. Rotation of the forearm in a supinated position (palm up) and/or wrist flexion increases the fluid pressure in the carpal tunnel. This increased pressure can result in compression of soft tissues like nerves, tendons and blood vessels, causing numbness in the thumb and fingers. :Corrective action: Forearm rotation angle near 45° pronation (palm down) should be maintained to minimize carpal tunnel pressure during repetitive activity. ;Clenched fist pipetting :Technique: Tight grip (clenched fist). Hand fatigue results from continuous contact between a hard object and sensitive tissues. This occurs when a firm grip is needed to hold a pipette, such as when jamming on a tip, and results in diminished hand strength. :Corrective action: Use pipettes with hooks or other attributes that allow a relaxed grip and/or alleviate need to constantly grip the pipette. This will reduce tension in the arm, wrist and hand. ;Thumb plunger pipetting :Technique: Concentrated area of force (contact stress between a hard object and sensitive tissues). Some devices have plungers and buttons with limited surface areas, requiring a great deal of force to be expended by the thumb or other finger in a concentrated area. :Corrective action: Use pipettes with large contoured or rounded plungers and buttons. This will disperse the pressure used to operate the pipette across the entire surface of the thumb or finger, reducing contact pressure to acceptable levels. ;Incorrect posture can have a strong impact on available strength arm strength pipetting :Technique: elevated arm. Muscle strength is substantially reduced when arm flexion is increased. :Corrective action: Keep work items within easy reach to limit extension and elevation of arm. Arm/hand elevation should also not exceed 12” from the worksurface. ;Elbow strength pipetting :Technique: Elbow flexion or abduction. Arm strength diminishes as elbow posture is deviated from a 90° position. :Corrective action: Keep forearm and hand elevation within 12” of the worksurface, which will allow the elbow to remain near a 90° position. Unlike traditional axial pipettes, ergonomic pipetting can affect posture and prevent common pipetting injuries such as carpal tunnel syndrome, tendinitis and other musculoskeletal disorders. To be "ergonomically correct" significant changes to traditional pipetting postures are essential, like: minimizing forearm and wrist rotations, keeping a low arm and elbow height and relaxing the shoulders and upper arms.


Pipette stand

Typically the pipettes are vertically stored on holder called pipette stands. In case of electronic pipettes, such stand can recharge their batteries. The most advance pipette stand can directly control electronic pipettes.


Alternatives

An alternative technology, especially for transferring small volumes (micro and nano litre range) is
acoustic droplet ejection Acoustic droplet ejection (ADE) uses a pulse of ultrasound to move low volumes of fluids (typically nanoliters or picoliters) without any physical contact. This technology focuses acoustic energy into a fluid sample in order to eject droplets as s ...
.


References


External links


Helpful Hints on the Use of a Volumetric Pipet
by Oliver Seely {{Laboratory equipment Laboratory glassware Laboratory equipment Microbiology equipment Volumetric instruments