Pipette

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Various pipettes and related items: 1) Adjustable pipettes, from left: 20-200 ml, 2-20 ml, 100-1000 ml; 2) Graded transfer pipette and electric pipette filler; 3) 25 mL, 10 mL, 5 mL, and 2 mL transfer pipettes; 4) Disposable tips for adjustable pipettes; 5) 12-channel adjustable pipette for microplates; 6) Low-retention 0.5-10 ml adjustable pipette; 7) Squeezable transfer pipettes; 8) Digital adjustable pipette; 9) Light-guided pipetting system Pipettes.jpg
Various pipettes and related items: 1) Adjustable pipettes, from left: 20–200 μl, 2–20 μl, 100–1000 μl; 2) Graded transfer pipette and electric pipette filler; 3) 25 mL, 10 mL, 5 mL, and 2 mL transfer pipettes; 4) Disposable tips for adjustable pipettes; 5) 12-channel adjustable pipette for microplates; 6) Low-retention 0.5–10 μl adjustable pipette; 7) Squeezable transfer pipettes; 8) Digital adjustable pipette; 9) Light-guided pipetting system

A pipette (sometimes spelled pipett) is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, often as a media dispenser. Pipettes come in several designs for various purposes with differing levels of accuracy and precision, from single piece glass pipettes to more complex adjustable or electronic pipettes. Many pipette types work by creating a partial vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid. Measurement accuracy varies greatly depending on the instrument.

Contents

History

The first simple pipettes were made in glass, such as Pasteur pipettes. 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 (Marburg, 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. [1] [2]

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 are distinguished as micropipettes, while macropipettes dispense greater volumes.

Common pipettes

Air displacement micropipettes

Single-Channel Pipettes designed to handle 1-5ml and 100-1000ul with locking system Single channel rack.jpg
Single-Channel Pipettes designed to handle 1–5ml and 100–1000µl with locking system
A 5,000 ml (5 ml) pipette, with the volume to be transferred indicated. 500 means that the amount transferred is 5,000 ml. P5000 pipette.jpg
A 5,000 μl (5 ml) pipette, with the volume to be transferred indicated. 500 means that the amount transferred is 5,000 μl.
A 1,000 ml (1 ml) pipette, with the volume to be transferred indicated. P1000 pipette.jpg
A 1,000 μl (1 ml) pipette, with the volume to be transferred indicated.
A variety of pipette tips Pipette tips-different 1.jpg
A variety of pipette tips

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:

Pipette typeVolumes (μL)Tip color
P100.5–10white
P202–20yellow
P20020–200yellow
P1000200–1,000blue
P50001,000–5,000white

These pipettes operate by piston-driven air 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 in Marburg, 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. [3]

Types of air displacement pipettes include:

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 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 due to repetitive pipetting, electronic pipettes commonly replace the mechanical version.

Single-Channel Electronic Pipettes designed to handle 0.5-10ml Air-displacement electronic pipette with maximim volume of 10mL.jpeg
Single-Channel Electronic Pipettes designed to handle 0.5–10ml
VIAFLO electronic multichannel pipettes from INTEGRA Biosciences VIAFLO-electronic-pipettes.jpg
VIAFLO electronic multichannel pipettes from INTEGRA Biosciences

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.

Volumetric pipettes

Several sizes of volumetric pipette. Vollpipetten.jpg
Several sizes of volumetric pipette.

Volumetric pipettes or bulb pipette 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). 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.

Graduated pipettes

Graduated pipettes are a type of macropipette consisting of a long tube with a series of graduations, as on a graduated cylinder or burette, 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.

Pasteur pipette

Pasteur pipettes with rubber bulbs attached. Pasteur Pipets.jpg
Pasteur pipettes with rubber bulbs attached.

Pasteur pipettes 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 pipettes, droppers, eye droppers and chemical droppers.

Transfer pipettes

A transfer pipette Plastic Pasteur pipette.jpg
A transfer pipette

Transfer pipettes , 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 burettes. They are calibrated to ISO volumetric A grade standards. A glass or plastic pipette tube is used with a thumb-operated piston and PTFE 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 with serologic pipettes for volumetric analysis. Invented by Donald Dexter Van Slyke. [4]

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, a Baltic German Chemist and later refined by Otto Folin, an American chemist. [5] [ failed verification ]

Glass micropipette

Carlsberg pipettes, glass micropipettes, named for the place for their invention and first use, The Carlsberg Laboratory, Physiology Department, Copenhagen, Denmark. Used with a mouthpiece for precision biochemical and physiological labwork. From the top: double constriction pipettes for 1 and 10 microlitre, single constriction pipettes for 200, 2,000, and 10,000 microlitre Carlsberg micropipettes.jpg
Carlsberg pipettes, glass micropipettes, named for the place for their invention and first use, The Carlsberg Laboratory, Physiology Department, Copenhagen, Denmark. Used with a mouthpiece for precision biochemical and physiological labwork. From the top: double constriction pipettes for 1 and 10 microlitre, single constriction pipettes for 200, 2,000, and 10,000 microlitre
Borosilicate glass micropipette pulled with a Flaming/Brown micropipette puller P-97 Pulled pipette.jpg
Borosilicate glass micropipette pulled with a Flaming/Brown micropipette puller P-97

These are used to physically interact with microscopic samples, such as in the procedures of microinjection and patch clamping. Most micropipettes are made of borosilicate, aluminosilicate or quartz 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.

Microfluidic pipette

A Microfluidic pipette, housed in a manifold holder. The colored solutions highlight the solutions loaded into the wells of the PDMS pipette. Pneumatic actuation is used to keep all tubing free of contamination. Multifunctional Pipette.jpg
A Microfluidic pipette, housed in a manifold holder. The colored solutions highlight the solutions loaded into the wells of the PDMS pipette. Pneumatic actuation is used to keep all tubing free of contamination.

A recent introduction into the micropipette field integrates the versatility of microfluidics 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 (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 [6] at Chalmers University of Technology in Sweden. [7]

Extremely low volume pipettes

A zeptoliter pipette has been developed at Brookhaven National Laboratory. 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 takes place. [8]

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; [9] a tablet can interact in real-time with the pipette and guide a user through a protocol; [10] and a pipette station can help to control the pipette tip immersion depth and improve ergonomics. [11]

Robots

An example of mechanical pipettes manipulated by an anthropomorphic robot Automated pipetting system using manual pipettes.jpg
An example of mechanical pipettes manipulated by an anthropomorphic robot

Pipette robots are capable of manipulating the pipettes as humans would do. [12]

Calibration

Pipette recalibration [13] 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. [14] 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. [15] 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

Smart pipette stand capable to control electronic pipettes Smart pipette stand.jpg
Smart pipette stand capable to control electronic pipettes

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. [16]

Alternatives

An alternative technology, especially for transferring small volumes (micro and nano litre range) is acoustic droplet ejection.

Related Research Articles

Pressure measurement Analysis of force applied by a fluid on a surface

Pressure measurement is the analysis of an applied force by a fluid on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure meters or pressure gauges or vacuum gauges. A manometer is a good example, as it uses the surface area and weight of a column of liquid to both measure and indicate pressure. Likewise, the widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge.

Pump Device that imparts energy to the fluids by mechanical action

A pump is a device that moves fluids, or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps.

Repetitive strain injury Medical condition

A repetitive strain injury (RSI) is an injury to part of the musculoskeletal or nervous system caused by repetitive use, vibrations, compression or long periods in a fixed position. Other common names include repetitive stress disorders, cumulative trauma disorders (CTDs), and overuse syndrome.

In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, a sound tone, or a physical artifact, such as a meter ruler.

A burette is a graduated glass tube with a tap at one end, for delivering known volumes of a liquid, especially in titrations. It is a long, graduated glass tube, with a stopcock at its lower end and a tapered capillary tube at the stopcock's outlet. The flow of liquid from the tube to the burette tip is controlled by the stopcock valve. There are two main types of burette; the volumetric burette and the Piston burette.

Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. The common types of flowmeters with industrial applications are listed below:

Desoldering

In electronics, desoldering is the removal of solder and components from a circuit board for troubleshooting, repair, replacement, and salvage.

Wristlock

A wristlock is a joint lock primarily affecting the wrist-joint and, in some cases, the radioulnar joints through rotation of the hand. A wristlock is typically applied by grabbing the opponent's hand, and bending and/or twisting it. Wristlocks are very common in martial arts such as aikido, hapkido and jujutsu where they are featured as self-defense techniques. They are also used as submission holds in martial arts such as Brazilian jiu-jitsu and catch wrestling. While being an illegal technique in modern sambo and judo competitions, it is still practiced in judo forms of self-defense kata kōdōkan goshinjutsu. Wristlocks are also widely used as pain compliance holds, often in police, military, and residential treatment centers.

An eye dropper, also known as a Pasteur pipette, or 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 eye drops into the eye. The commonly recognized form is a glass tube tapered to a narrow point 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. 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.

Hydraulic pump

Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or hydrodynamic. A hydraulic pump is a mechanical source of power that converts mechanical power into hydraulic energy. It generates flow with enough power to overcome pressure induced by the load at the pump outlet. When a hydraulic pump operates, it creates a vacuum at the pump inlet, which forces liquid from the reservoir into the inlet line to the pump and by mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system. Hydrostatic pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement cannot be adjusted, or variable displacement pumps, which have a more complicated construction that allows the displacement to be adjusted. Hydrodynamic pumps are more frequent in day-to-day life. Hydrostatic pumps of various types all work on the principle of Pascal's law.

The Ballard Maturational Assessment, Ballard Score, or Ballard Scale is a commonly used technique of gestational age assessment. It was devised by Dr Jeanne L Ballard, Professor Emeritus of Pediatrics, Obstetrics and Gynecology at the University of Cincinnati College of Medicine.

A volumetric pipette, bulb pipette, or belly pipette allows extremely accurate measurement of the volume of a solution. It is calibrated to deliver accurately a fixed volume of liquid.

Air displacement pipette

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 susceptible to damage from many organic solvents.

Graduated pipette

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. Along the body of the tube are graduation markings indicating volume from the tip to that point. A small pipette allows for more precise measurement of fluids; a larger pipette can be used to measure volumes when the accuracy of the measurement is less critical. Accordingly, pipettes vary in volume, with most measuring between 0 and 25.0 millilitres.

Automated pipetting system


An automated pipetting system is generally a device which performs programmed transfers of liquid between preselected groups of containers.

Forward pipetting is a technique to dispense a measured quantity of liquid by means of air displacement pipette. The technique is mainly recommended for aqueous solutions, such as buffers, or diluted acids or alkalis. In case of solutions with a high viscosity or a tendency to foam, reverse pipetting is more suitable.

Reverse pipetting is a technique to dispense a measured quantity of liquid by means of air displacement pipette. The technique is mainly recommended for solutions with a high viscosity or a tendency to foam: as it reduces the risk of splashing, foam or bubble formation. Reverse pipetting is more precise in dispensing small volumes of liquids containing proteins and biological solutions compared to forward pipetting, which is mostly used for aqueous solutions, such as buffers, diluted acids or alkalis.

Media dispenser


A media dispenser or a culture media dispenser is a device for repeatedly delivering small fixed volumes of liquid such as a laboratory growth medium like molten agar or caustic or volatile solvents like toluene into a series of receptacles. It is often important that such dispensers operate without biological or chemical contamination, and so must be internally sealed from the environment and designed for easy cleaning and sterilization before use. At a minimum, a media dispenser consists of some kind of pump connected to a length of discharge tubing or a spout. Dispensers used in laboratories are also frequently connected to microcontrollers to regulate the speed and volume of the medium as it leaves the pump.

Heinrich Schnitger

Heinrich Schnitger was a German physician. He is considered the inventor of the piston stroke Micropipette, a laboratory device for dispensing small amounts of liquid.

Positive displacement pipettes are a type of pipette that operates via piston-driven displacement. Unlike an air displacement pipette, which dispenses liquid using an air cushion in the pipette tip, the piston in a positive displacement pipette makes direct contact with the sample, allowing the aspiration force to remain constant.

References

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  10. "TRACKMAN Connected". www.gilson.com.
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