BIOTIX INC. THE BIOTIX GUIDE TO PIPETTING understand and get the most out of your pipettes to get better results in your experiments
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Biotix Inc. Technological breakthroughs found only in the most advanced liquid handling tools available. http://biotix.com/ [email protected] +1 858 875 7696 01 | THE HISTORY OF PIPETTE DESIGN 0
02 | TYPES OF PIPETTES 2
03 | FINDING THE RIGHT PIPETTE TIP 4
04 | CARING FOR AND MAINTAINING YOUR PIPETTE 8
05 | ERGONOMICS AND PIPETTING IN THE LAB 10
06 | SUSTAINABILITY 12
07 | FURTHER READING 14 TABLE OF TABLE CONTENT CHAPTER 1 THE HISTORY OF PIPETTE DESIGN 4 THE HISTORY OF PIPETTE DESIGN
In the 19th century, Louis Pasteur needed a way to Contrary to popular belief, the earliest pipettes 3 transfer small amounts of liquid without contamination. 1 were created not by Louis Pasteur in the 19th He would take a glass tube, heat the center over a burner, century but in the 18th century by two French chemists, draw the tube out to make it very thin in the center, and Francois Descroizilles and Joseph-Louis Gay-Lussac. then snap it in half to yield two fine-tipped pipettes. The Descroizilles in particular is considered the patriarch of fine-tipped end was placed in liquid and a balloon or rubber the volumetric analysis field. He created the precursor bulb was placed on the larger diameter end. When the bulb to today’s buret and pipettes called the berthollimetre was squeezed, it creates a vacuum that draws liquid into and alcalimetre, respectively. In an 1824 paper, Gay- the pipette. Similar pipettes are still used today in this form Lussac made some modifications to the alcalimetre and or as an all-in-one plastic version, which is referred to as a coined the resulting instrument a “pipette.” transfer pipette. Typically, a transfer pipette does not have measurement markings and are not meant for transferring accurate amounts of liquid. Descroizilles’s and Gay-Lussac’s pipettes are most 2 similar to the modern day serological pipette. Today’s serological pipettes are either made of disposable plastic or
reusable glass. Like Descroizille’s design, these pipettes have a gradation scale on the side to accurately measure and transfer between a fraction of a milliliter and 50 mL of material. In use, serological pipettes are inserted in to a pipette plunger apparatus. When depressed, the plunger creates a partial vacuum that allows the liquid to be drawn up in to the serological pipette. The user can easily control the amount of liquid drawn in to the pipette.
Francois Descroizilles and Joseph-Louis Gay- Lussac created the first pipettes in the 18th century.
Like most modern day pipettes, they transfer between a fraction of a milliliter and 50 mL of material.
In the 19th century, Louis Pasteur needed a way to transfer small amounts of liquid without contamination.
THE BIOTIX GUIDE TO PIPETTING 5 THE HISTORY OF PIPETTE DESIGN
Heinrich Schnitger, a postdoctoral student at the The Carlsberg pipettes took Pasteur pipettes one 5 University of Marburg, Germany was frustrated with 4 step further. In the 1930s, Kaj Ulrik Linderstrøm– trying to accurately draw small volumes of materials using Lang in the Carlsberg laboratory in Denmark wanted to the Carlsberg pipette. To overcome this issue, he created study single cell metabolism. He passed the problem a piston-pump driven glass pipette starting from a syringe. of scaling down the typical laboratory techniques to a His design created a more accurate and durable pipette that research fellow named Milton Levy. For his research, didn’t require mouth pipetting. He was awarded a patent for Levy created the first reported pipette for small his design in 1961. Schnitger’s pipette design was adopted measurements. Similar to Pasteur, he made these by the scientific device industry and this basic design is still pipettes by drawing a glass tube over a lit Bunsen used today. burner and pulling one end to create a thin, capillary tube. However, each pipette was then calibrated with mercury or dye to measure a specified volume of liquid. Also, the liquid was drawn into the pipette by For his research, Levy created the first reported mouth pipetting—a technique in which the scientist pipette for small measurements. uses his/her mouth to suck up the liquid into the pipette. Schnitger’s design created a more accurate Carlsberg pipettes had a number of limitations—they and durable pipette that didn’t require mouth pipetting. were not consistently manufactured (though some were mass-produced), broke easily, did not ensure accurate volumes despite calibration, required extensive experience, and could cause the user to ingest whatever was being drawn up in to the pipette.
THE BIOTIX GUIDE TO PIPETTING CHAPTER 2 TYPES OF PIPETTES 7 TYPES OF PIPETTES
While micropipettes have been developed in all sizes to address specific laboratory tasks, mechanistically there are two main types: Air displacement and positive displacement. In overall basic mechanism, both air and positive displacement pipettes are similar.
Both types of micropipettes work similarly to Schnitger’s basic pipette design. Both pipettes require depression of a piston-driven plunger. The user sets the volume to be drawn up prior to pressing the plunger. Depressing and releasing the plunger creates a vacuum that draws the set amount of liquid up into the pipette. However, because of slight differences in design and how the sample is drawn up, they are used for very different purposes and materials in the lab.
THE BIOTIX GUIDE TO PIPETTING 8 TYPES OF PIPETTES
Figure 1. Comparison of Air Displacement and Positive Displacement Pipettes.
AIR DISPLACEMENT
Air displacement starts with dialining in your volume which moves the internal piston to the correct position to be able to draw the appropriate volume. Once that volume is set you depress the plunger which moves
the piston down in the pipette. Once you emerge the tip into the liquid is when the vacuum is created and once you release the button the piston moves up and aspirates the liquid to whatever setting you put on the pipette. Once you have the sample in the pipette tip and you push the plunger again the piston will move back towards the position you drew the liquid from. Then the blowout stage which is fully pressing the top button pushes the piston past its position when you began the draw which creates pressure greater than the volume drawn making it expel all the remaining liquid.
THE BIOTIX GUIDE TO PIPETTING 9 TYPES OF PIPETTES
A key feature of air displacement pipettes is that a cushion of air is left between the pipette shaft and the sample, so the sample is never allowed to come into contact with the shaft. This, in combination with the use of disposable pipette tips makes air displacement pipettes very convenient for repeated, routine, accurate pipetting work. In biological labs for example, air displacement pipettes are the instrument of choice for measuring most aqueous solutions and buffers, including common biological materials like DNA, RNA and proteins.
The downsides of the air displacement mechanism are that the accuracy of the pipettes is affected by temperature, atmospheric pressure, and density/viscosity of the sample. In addition, the air cushion can allow highly volatile samples to evaporate into the air space, which can lead to contamination of the pipette.
Fixed volume Single channel Calibrated to dispense one volume One pipette tip per pipette
Variable/adjustable volume Multi-channel Can change and set volume dispensed One pipette holds many tips that by pipette simultaneously measure and dispense the same volume of liquid (often used with multi-well plates Manual Manually press and depress plunger Repeat function (repeaters) A larger volume is taken up into a Electronic reservoir. The sample volume is taken up and dispensed with a push of a button Pipette operated by battery force
THE BIOTIX GUIDE TO PIPETTING 10 TYPES OF PIPETTES
POSITIVE DISPLACEMENT PIPETTES
Positive displacement pipettes act more like In comparison to air displacement pipettes, syringes. A disposable barrel/tip is placed the types of positive displacement pipettes on to the pipette (see Figure 1). The desired are limited. They are generally only available pipetting volume is selected and the piston as repeat or manual, single channel variable moves down into the disposable barrel. The pipettes. piston comes into direct contact with the sample so no air cushion exists between the sample and the piston. When the plunger is released, a partial vacuum draws the liquid up into the barrel. To release the sample, the plunger is pressed again and the piston pushes the liquid out of the barrel. The entire barrel/tip is disposed of between samples. A positive displacement pipette applies constant aspiration force to the sample that is not affected by the physical characteristics of the sample. Therefore, they are useful for accurately pipetting viscous or dense solutions. They are also used to pipette corrosive or radioactive samples to prevent contamination of the pipette as well as cross- contamination between samples. Positive displacement pipettes are also used when working with volatile samples that would be susceptible to evaporation in the air cushion of air displacement pipettes.
THE BIOTIX GUIDE TO PIPETTING 11 TYPES OF PIPETTES
Figure 2. Exploded Diagram of an Air Displacement Pipette.
THE BIOTIX GUIDE TO PIPETTING CHAPTER 3 FINDING THE RIGHT PIPETTE TIP 13 FINDING THE RIGHT PIPETTE TIP
In the days of mouth-drawn Pasteur pipettes (and even earlier), one size of pipette tip had to fit all applications. But today’s technology has advanced to the point where there many types of tips are available to suit a myriad of applications. Picking the right tip for your application is important. In fact, the tip is one of the most important factors in accurate pipetting – it is at least as important as calibration and pipetting technique. A well-calibrated pipette isn’t very helpful if the wrong type of tip is used. In addition, using the wrong tip can lead to contamination, and even force you to exert more force while pipetting, leading to repetitive stress injuries. The sheer variety of available tips can be confusing, but this guide will help you make the best choice for your needs.
GENERAL CONSIDERATIONS WHEN CHOOSING A TIP
QUALITY
Pipetting must be precise and accurate—that is, you The design of the tip is also critical. While it may must be able to consistently deliver the exact amount seem like just a piece of plastic, many features of a of material in precisely the right location. This requires pipette tip can improve performance. One example tips that are manufactured to reduce any variation in is BLADE® technology by Biotix in which the distal volume and sample delivery. That means you should end of the pipette tip has an optimal bore size to wall avoid cheaper tips that may have manufacturing thickness. This prevents droplet formation reducing imperfections such as flashes, protrusions, scratches, touch-off and save you time with each aspiration. air bubbles, bends or impurities. Also, make sure there is little tip-to-tip variation in a batch of tips. Finally, be aware that some lower quality tips may contain additives in the plastic that can contaminate samples and affect experiments.
THE BIOTIX GUIDE TO PIPETTING 14 FINDING THE RIGHT PIPETTE TIP
FIT PRICE
Tips should fit snugly on to the end of your pipette. Pipette tips represent a small cost compared to This ensures precision, avoiding any aspiration of time and reagents. Pipette tip costs can vary greatly air into the pipette as you draw samples. Tips should depending on the design of the tip and the materials it also release easily from the pipette without falling is made from. One way to reduce costs is to purchase off prematurely. Poor fitting tips can lead to sample high quality tips delivered in a reload format. Reloads leakage and may require additional insertion force allow you to rack tips in seconds saving you time, and contributing to repetitive stress injury. Biotix tips come come in a multitude of formats to fit your budget. with FlexFit® technology and “flex” at the insertion end Figures 3 & 4. Packaging to provide a better fit on a variety pipette types. of Bulk Tips.
THE BIOTIX GUIDE TO PIPETTING 15 FINDING THE RIGHT PIPETTE TIP
UNIVERSAL VERSUS BRAND SPECIFIC
Most pipettes are compatible with universal pipette tips. However many pipette manufacturers recommend using their brand-specific tips designed for use with their pipettes. In most cases this is unnecessary, but there are a few pipettes on the market that require a specific pipette tip. When selecting pipettes consider whether or not a specific tip is required versus universal. The requirement of a specific pipette tip can lead to higher costs and disruptions in supply. In addition, if brand-specific/pipette-specific tips are used, then each brand of pipette used in the lab will require purchase of a different tip. Therefore, the most economical choice is to use universal pipettes and tips. Universal tips are designed to fit most commercially available pipettes containing a standard-diameter barrel. These tips meet a large number of laboratory requirements, including reagent transfer and high accuracy measurements and can be used for a wide variety of applications, as long as they are of good quality and fit your pipette snugly.
THE BIOTIX GUIDE TO PIPETTING 16 FINDING THE RIGHT PIPETTE TIP
BARRIER (OR FILTER) TIPS
Barrier, also called filter, tips contain material near the proximal end of the tip that prevents your samplefrom contaminating your pipette or damaging your equipment. The filter works by protecting the pipette barrel from aerosols and liquids during aspiration of samples. This prevents contamination of the pipette and subsequent samples. Filter tips are essential when working with toxic or caustic solvents or radioactivity. They are also used when conducting experiments that require the highest level of purity, such as with PCR or RNA.
Tip Types
Figure 5. Tip With no Barrier Compared to Tip With Figure 6. Pipette Tip Without Low-Retention Technology Barrier.
THE BIOTIX GUIDE TO PIPETTING 17 FINDING THE RIGHT PIPETTE TIP
LOW RETENTION STERILE AND DNASE/RNASE FREE
In many standard pipette tips a tiny amount of residual Sterile tips are treated with radiation to eliminate liquid will to cling to the sides of the tip after aspiration living organisms. They are packaged and shipped in and dispensing due to the properties of the resin that the individual boxes. DNase/RNase-, endotoxin-free tips tip is made. Low retention pipette tips are manufactured undergo additional rounds of sterilization to remove all in two ways: from material that is hydrophobic or contaminants. These tips are typically used for highly batch coated with a hydrophobic material. Typically sensitive experiments, such as PCR. manufacturing from a hydrophobic material is superior. A cheaper alternative to purchasing pre-sterilized tips Batch coating can be variable among tips negatively is to purchase tips in bulk, and sterilize the racked tips impacting precision. using an autoclave. This is most useful for tips to be used in less sensitive, routine applications.
Figure 8. Sterile, Pre-Racked Pipette Tips.
Figure 7. Pipette Tip With Low-Retention Technology
THE BIOTIX GUIDE TO PIPETTING 18 FINDING THE RIGHT PIPETTE TIP
OTHER TYPES GRADUATED TIPS
Many other tip types are available for specialty Graduated tips contain measurement markings on applications. For example, wide orifice/bore tips have the side of the tip. They enable the user to visually larger openings for pipetting more viscous fluids. determine that the right volume is aspirated each time. Gel loading tips contain a thinner drawn out tip for These graduations are not exact but can help avoid accessing wells. large mistakes.
Figure 9. Image of Gel-Loading Tip
SELECTING THE BEST TIP FOR YOUR LAB
1. Do you need a specific pipette type for your pipette? Check around there may be multiple companies selling pipette tips compatible with your pipette.
2. Are you working with sticky samples such as protein or DNA? You may want to consider low retention tips
3. Are you performing PCR or a highly sensitive application? Sterile, DNase free/RNase free barrier tips would be the best choice to prevent carry-over and contamination.
4. Are you working with hazardous samples such as human blood, radioactive, or corrosive material? A barrier tip that seals will protect your pipette from contamination.
THE BIOTIX GUIDE TO PIPETTING CHAPTER 4 CARING FOR AND MAINTAINING YOUR PIPETTE 20 CARING FOR AND MAINTAINING YOUR PIPETTE
PIPETTING TECHNIQUE ADVICE
The pipette is a sophisticated and precise piece of Proper pipetting technique will prevent damage to technology that requires proper care and handling. the piston and other internal mechanisms of the pipette. It will also keep the pipette barrel free from Dirt, dust, and residual liquids affect its performance. contamination. Your pipette requires calibration on a regular basis to Always make sure your movements are smooth maintain its precision and accuracy. Most damage to and consistent. This prevents jarring of the pipettes arises from improper handling. For example, internal mechanisms of the pipette. the user drops the pipette on the lab bench and causes damage to the pipette barrel, or incorrect Operate your pipette in a vertical position to prevent liquids running along the shaft of the pipetting technique/pipette tip choice causing pipette. contamination inside the shaft.
Don’t dial a volume that is outside the limits of your pipette (this can also damage internal mechanisms). Use a pipette with a suitable capacity instead. STORING OF YOUR PIPETTE
How you store your pipette when it’s not in use is just as Don’t let the piston snap back up into place important as how you use it. For example, using a pipette when aspirating—this can lead to liquid backup and contamination of the shaft’s interior. stand to store your pipettes prevents the instrument from being accidentally knocked to the ground and keeps your pipettes organized. Storing pipettes upright prevents any liquid that might have accidentally been aspirated into the barrel from running further into the pipette—possibly even to the piston.
When not using your pipettes, store them upright and away from liquid.
Never store your pipettes on their side, and never store them with liquid in their tips.
Always use a pipette stand that fits your pipettes.
THE BIOTIX GUIDE TO PIPETTING 21 CARING FOR AND MAINTAINING YOUR PIPETTE
PROPER CLEANING OF YOUR PIPETTES
Nearly all pipette manufacturers provide cleaning instructions that won’t harm your pipettes. The manufacturer’s instructions should contain information about safe products to clean the inside of the pipette, and, for example, how to clean after using radioactive substances. Because certain cleaning products and procedures can harm different pipettes, be sure to check their instructions before starting any cleaning procedure. However, there are some general cleaning steps that are helpful for any pipette:
Wipe pipettes down with a 70 % ethanol solution every day.
Visually inspect your pipettes for damage every time you use them.
Learn how to remove the pipette barrel to clean inside (using the manufacturer’s instructions as a guide).
Organic solvents (and proteins) can be removed with a detergent solution, as long as the detergent doesn’t damage the pipette.
You can eliminate DNA by immersing pipette parts in at least 3% (w/v) sodium hypochlorite, for at least 15 minutes. Rinse well with distilled water and allow to dry. Some manufacturers have specialized solutions for removing DNA. RNA degrades quickly, and doesn’t require any special treatment to remove.
Autoclaving can be helpful, but for some types of pipettes, only certain parts may be sterilized in this way. Always check manufacturer’s guidelines in advance because autoclaving can destroy pipettes that are not suitable for autoclaving!
THE BIOTIX GUIDE TO PIPETTING 22 CARING FOR AND MAINTAINING YOUR PIPETTE
CALIBRATION
Calibrating a pipette involves testing it to determine if the dispensed volume is equal to the measured volume. If those two values aren’t the same, then your pipette needs calibration. All pipettes are calibrated at the factory, but repeated use (and maintenance issues) call for periodic recalibration. Manufacturers will disclose precision limits for their pipettes, but these may be more exact than are necessary for your lab. You must determine the necessary precision for your experiments.
HOW TO CALIBRATE PIPETTES
1. The calibration testing should take place in a 5. Repeat step 4 but dispense the second draft-free room at a constant temperature between calibration point’s volume. 20°C to 25°C.
2. Relative humidity should be above 45%, 6. Verify the weights you’ve collected to be within especially for volumes under 50 µL. Keep the the published pipette manufacturers systematic pipette in this room for at least two hours to error range. acclimate.
3. Choose two points that are published in the user 7. If the volumes fall outside of the published range, manual by your pipette manufacturer to calibrate you may do the calibration adjustments yourself or against. Nominal and 10% of nominal are usually send it out to a repair facility. published.
4. Using distilled water, dispense the first calibration point’s volume onto an analytical balance. Record the weight. Repeat this process ten times.
Calibrations should be done every 6 to 12 months. If you see worn O-rings, they should also be replaced as needed. Your lab should have a procedure to regularly do self checks in between scheduled calibrations
THE BIOTIX GUIDE TO PIPETTING 23 CARING FOR AND MAINTAINING YOUR PIPETTE
CALIBRATION: DO IT YOURSELF OR SEND IT OUT?
Electronic pipettes should be calibrated by the manufacturer or another specialized and trusted facility, because of the wide variety of features and construction methods for each type of pipette. For manual pipettes, some adjustments can be made in the lab using the following tips:
All adjustments are made at the lowest volume.
A service tool should have come with the pipette. If one did not, then you can order this from the manufacturer.
Place the service tool that came with the pipette into the opening of the calibration nut at the top of the handle.
Place the service tool that came with the pipette into the opening of the calibration nut at the top of the handle.
After adjusting, check the calibration again using the process outlined above.
www.Calibrate-It.com is a useful resource when carrying out your own calibrations. If these steps don’t help, then send the pipette out.
THE BIOTIX GUIDE TO PIPETTING 24 CARING FOR AND MAINTAINING YOUR PIPETTE
TROUBLESHOOTING YOUR PIPETTE
From time to time, your pipette will not behave as it should, and the tips below may help you solve some of most basic issues you might encounter:
Pipette tips drip or leak: This is probably the most commonly encountered pipetting 1. issue, and can easily occur if tips are loosely fitted, or if inappropriate tips are used.You can solve this by ensuring that your tips fit your pipettes, and/or by checking the pipette barrel for damage.
The pipette aspirates and dispenses inaccurate volumes: This can occur for a 2. number of reasons, including pipetting outside the range of your pipette, leaking tips (see 1. above), or the pipette is in need of calibration.
The dispensing button is stiff and doesn’t release smoothly: This may occur if the 3. seal gets swollen by reagent vapors and can usually be solved by opening the pipette and allowing it to ventilate. The piston can be lubricated if necessary.
If your pipette stops functioning completely, and the simple tips above don’t help you then don’t despair, but do send your pipette out for repair!
THE BIOTIX GUIDE TO PIPETTING CHAPTER 5 ERGONOMICS AND PIPETTING IN THE LAB 26 ERGONOMICS AND PIPETTING IN THE LAB
Many scientists do not think about the impact of pipetting on their long-term health. However pipetting has been identified as a risk for repetitive stress injury (RSI). Ergonomics is the study of how our work and othercommon activities affect our physical (in particular our musculoskeletal) health. In the lab, it focuses on how repetitive and forceful activities, as well as our sitting and standing postures, can cause pain and eventually damage to our bodies.
WHY SHOULD WE PRACTICE ERGONOMIC PIPETTING?
Much of the work we do in the lab (and many other workplaces) can lead to back pain, RSI and other issues over time, all depending on the nature of the work. In the lab, we are much more likely to become injured if we use the wrong equipment, or if we use appropriate equipment in the wrong way.
One common source of RSI and other lab-related work injury stems from pipetting. You may experience RSI as a numbness around your basal thumb joint, an ache in your wrist, or a general weak feeling in your hand. These symptoms occur because of the repetitive nature of pipetting and the force you apply when doing so. The symptoms associated with RSI may also extend into your back and shoulders causing you great discomfort.
Force in pipetting comes from attaching the pipette tip, dispensing the contents, ejecting pipette tips, and keeping a tight grip on a poorly designed pipette. Pipetting is usually very repetitive, and any laboratory worker might go through thousands of pipetting motions every single day. Pipetting for only one hour a day, over the course of a year, can put you at risk for RSI!
THE BIOTIX GUIDE TO PIPETTING 27 ERGONOMICS AND PIPETTING IN THE LAB
CHOOSE AN ERGONOMIC PIPETTE AND ERGONOMIC TIPS
Older pipette models require a lot of manual force on the plunger and the ejector button, which leads to more muscle strain than modern pipettes.
Look for more advanced pipettes that have low profile ejector buttons to reduce ejection force.
Ejection forces can vary greatly between pipette types, so it is important to test and select the one with the least force required.
Learn how to remove the pipette barrel to clean inside (using the manufacturer’s instructions as a guide).
Use well-fitting tips such as Biotix with a flexible proximal end (“FlexFit”). This flexing end forms a secure seal with your pipette barrel, eliminating banging or rocking. You should not have to twist your wrist or pound the tip into the end of pipette to get a good fit.
Figure 10. Demonstration of Flexible Fit at the Proximal End of the Tip.
THE BIOTIX GUIDE TO PIPETTING 28 ERGONOMICS AND PIPETTING IN THE LAB
PREPARE YOUR WORKSPACE BE ERGONOMIC – BE KIND TO YOURSELF!
Using proper pipetting technique and practicing good posture will go a long way in helping you avoid RSI Make sure your work area is clean, clear and and other pipetting-related injuries. You can be kind to organized. yourself by keeping the following in mind:
Arrange your most commonly used reagents so that you can reach them easily. Keep an eye on your posture. Sit up straight with your arms straight out.
Make sure you have a waste disposal bucket nearby on the side that suits you best. Position yourself so that you can pipette without reaching too far. Don’t hunch over or keep your arms elevated for any extended period of time. Pour liquids into smaller vessels so they are easier to reach, and keep your pipette tips at bench level (don’t try reaching for them up on a shelf). Take breaks! If you have hours of pipetting work ahead, don’t do a marathon session. Get up, stretch, walk around a little bit, and then start working again.
Remember that the U.S. Occupational Health and Safety Administration (OSHA) recommends taking a 2-minute break every 20 minutes.
As mentioned earlier, RSI is only one-lab related injury, and pipetting is only one cause of RSI. Continuous pain or pain that doesn’t subside when practicing ergonomic pipetting should be addressed by a doctor. From time to time physiotherapy may be necessary to treat RSI. Luckily, it’s very easy to reduce the risk of pipetting-associated RSI by following the ergonomic tips provided here. Don’t be afraid to take that 2-minute break!
THE BIOTIX GUIDE TO PIPETTING CHAPTER 6 FURTHER READING 30 FURTHER READING
History of Pipettes: 1. Duval C. (1951) Francois Descroizilles, the inventor of volumetric analysis. J. Chem. Educ. 28(10):508–19. 2. The Rockefeller University: Science Outreach Program. Origins of the Pipette: Why Today’s Scientists Don’t Need to Use Their Mouths. 3. Klingenberg M. (2005) When a common problem meets an ingenious mind. EMBO Reports 6:797-800. 4. JoVE. Introduction to Serological Pipettes and Pipettors. 5. Sella A. (2014) Schnitger’s pipette. Chemistry World.
Pipette Tips: Here are some more references to help with tip selection. 1. Bitesize Bio Biotix article 2. http://biotix.com/technology/
Ergonomic Pipeptting: 1. Bitesize Bio Biotix article
THE BIOTIX GUIDE TO PIPETTING