The pipette is a reliable precision instrument that has been used and trusted for many years. However, as with many forms of instrumentation, a pipette will perform only as well as the operator’s technique allows.
Differences in technique – some more than others – can alter delivery volumes. With increasing demand for accuracy, quality and productivity the importance of understanding and developing optimal pipetting technique becomes imperative. Let’s review the results of a study conducted at Artel to determine these differences and assess their impact upon pipetting accuracy.
The reference pipetting method used in each of these experiments was as follows: The pipette mechanism was “warmed up” by gently depressing and releasing the plunger 15 to 20 times. The pipette tip was prewet by aspirating and dispensing an aliquot of the sample solution three times.1 With the plunger depressed to the first stop, the tip was immersed approximately one millimeter into the sample solution and held there for a half second. The aliquot was aspirated from the sample solution by gently releasing the plunger, keeping the tip in the sample solution for two seconds before removal.
The aliquot was delivered by placing the pipette tip on the side of a glass vial at a 45° angle just above the meniscus and slowly depressing the plunger past the first stop to deliver the entire aliquot.
Each experiment consisted of two runs of ten data points each, using an adjustable 20 μL Eppendorf manual action air displacement pipette† set at 5 μL and Eppendorf disposable pipette tips, on the Artel PCS® Pipette Calibration System. Each experiment was performed as a comparison of one pipetting technique versus another.
The results for each pair of techniques were compared concerning trueness and precision. The measurement used for rating the precision of each technique was the coefficient of variation (%CV). Trueness was defined as the percent difference in mean delivery volumes between the two pipetting techniques.
The greatest discrepancies observed during this study were the differences between dry and prewetted pipette tips. Dry pipette tips consistently delivered significantly lower volumes than did the prewetted tips, a fact which other researchers have noted.2-6 No difficulty with precision was observed using either prewetting or no prewetting. However, differences in trueness of up to 7% between runs using dry and prewetted tips were noted while using the 20 μL pipette set at 5 μL. Additional experiments using a 250 μL pipette set at 25, 50, 100 and 250 μL consistently showed differences in the trueness of the volume pipetted of up to 2%.
Prewetting the pipette tip influenced trueness by increasing the humidity within the tip, thus minimizing evaporation of the solution. Similarly, increased ambient humidity minimized evaporation. The beneficial effect of prewetting was less significant with high ambient humidity. Ambient humidity for these runs was 50%.
Variation in the temperature of the solution being pipetted was observed to be the second largest cause of pipetting error in this study. Three sample solutions were brought to three different temperatures: 8.5, 25 and 30 °C. Solutions that were warmed to 30 °C consistently delivered lower volumes than room temperature samples. Similarly, solutions that were cooled to 8.5 °C delivered higher volumes than the ambient (25 °C) sample. The differences observed in this study were significant, ranging from 3 to 7%. Figure 1 below shows the effect of sample temperature on pipetting trueness.
Experiment showing the effect of sample temperature on the trueness of pipetting results, using a 20 µL adjustable air displacement pipette set at 5 µL. Ambient temperature 25.0 °C.
In addition to trueness problems seen with samples that were not at room temperature, there was some difficulty in obtaining good precision. Runs typically produced between 0.5% and 1.0% CV, although the CV went as high as 3.6% in some cases. As the solution was allowed to approach room temperature, the precision of the results improved. Similarly, if the pipette end or tip was warmed, even just by casual handling, differences in delivery volumes were observed. These differences and inconsistencies were smaller and less significant than those resulting from variations in solution temperature.
Reverse mode pipetting is a method of pipetting commonly used with viscous liquids. This is a technique in which the plunger is depressed past the first stop to aspirate the aliquot from the sample, and depressed only to the first stop to deliver the aliquot. Reverse mode pipetting can make obtaining accurate results (for the pipetting of solutions similar to water in terms of density and surface tension) more difficult. The study showed that a typical precision for reverse mode was 1.4% CV. Differences in volumes delivered by standard and reverse mode techniques ranged up to 5%. The reverse mode consistently delivered a higher volume than the standard method of pipetting.
Techniques among pipette users vary with background, personal preferences, and training. These differences in execution can affect the accuracy, precision and trueness of results being released from the clinical or research lab. To ensure pipetting accuracy, facilities should adopt standard operating procedures for pipetting techniques and ensure that all operators are trained to an adequate level of proficiency. By increasing the level of consistency in results obtained, the level of quality and credibility of the facility will be enhanced.
Other error causing techniques8 include:
Individually none of these factors resulted in an error greater than 2%. Cumulatively, however, two or more of these sources of error (e.g., prolonged delay and rate of plunger depression) could affect delivered volume significantly.
Component failure (e.g., a plunger seal or corroded piston), incorrect pipette tip, or incorrect installation of the tip can also affect your results.
†In an air displacement pipette, many sources of pipetting error are magnified by the ratio of “dead air” above the liquid level to the liquid volume in the tip.2-6 In conducting these experiments, a 20 μL pipette was used to deliver 5 μL, so the amount of dead air was increased, compared to pipetting 20 μL with the same pipette.
1. Zeman GH, Mathewson NS. “Necessity of prerinsing disposable polypropylene pipet tips,” Clin Chem 1974; 20(4)497-8.
2. Sternberg JC. “Sampling with air-piston pipettes – a critical study,” Clin Chem 1975; 21(7):1037.
3. Ellis KJ. “Errors inherent in the use of piston activated pipettes,” Anal Biochem 1973; 55:609-14.
4. Wenk RE, Lustgarten JA. “Technology of manually operated sampler pipettes,” Clin Chem 1973; 20(3):320-3.
5. Joyce DN, Tyler JPP. “Accuracy, precision and temperature dependence of disposable tip pipettes,” Med Lab Technol 1973; 30:331-4.
6. Lochner KH, Ballwegt, Fahrenkrog HH. “Factors influencing the measuring accuracy of piston pipettes with air interface (German),” J. Lab Med 1996; 20(7/8)430-440.
7. Ylätupa Dr. S. “Choosing a Pipetting Technique Affects the Results of Your Analysis,” European Clinical Laboratory 1996. 10:14.
8. 10 Tips To Improve Your Pipetting Technique: artel.co/resource-library/10-tips-to-improve-your-pipetting-technique/
Keeping a continual focus on optimizing laboratory productivity, particularly in an increasingly global environment, Bjoern has been contributing to the development of international standards for over 10 years. He is a technical expert contributing to the efforts of standards development committees of ISO (International Standards Organization), ASTM International (formerly the American Society for Testing and Materials), and CLSI (Clinical and Laboratory Standards Institute).
Filling a void in testing guidance for users of automated liquid handling systems, Bjoern was one of the industry experts who proposed the development of the ISO International Workshop Agreement (IWA) 15 “Specification and method for the determination of performance of automated liquid handling systems,” serving as project leader and technical editor for the development of this ISO document. He is currently the project leader and technical editor for the development of a series of ISO standards (ISO 23783 parts 1, 2, and 3) slated to succeed ISO/IWA 15.
Bjoern has been contributing as technical expert to the revision of the ISO 8655 series of standards, serving as lead author and project leader for the new Part 8 “Photometric reference measurement procedure for the determination of volume” and project leader and technical editor for the revision of Part 7 “Alternative measurement procedures for the determination of volume.” He is the co-proposer, lead author, and project leader for the development of the new Part 10 “User guidance and requirements for competence, training, and POVA suitability.”
Key Roles:
Project leader for development or revision of:
– ISO 8655-7
– ISO 8655-8
– ISO 8655-10
– ISO 23783-1, -2, and -3
– ASTM E1154
– ISO/IWA 15
Technical expert in:
– ISO/TC48/WG04
– ISO/TC48/WG05
– ANSI US TAG to ISO/TC48
– ASTM E41 and E13
– CLSI
Heidi contributes almost 40 years of Regulatory Affairs and Quality Assurance experience to the Standards Leadership team. Having worked for decades in FDA-registered companies, she is well-versed in FDA regulations, audits, and inspections. As a Certified QMS Auditor, she has been responsible for all aspects of Artel’s ISO 9001 certification and ISO 17025 accreditation processes, as well as the corresponding internal audits. Additionally, she is an expert in industry-specific regulatory requirements, and ensures Artel’s continuous compliance with all applicable regulations and international standards.
Heidi serves as the secretary to the ISO working group responsible for the development of a series of new ISO standards for Automated Liquid Handling Systems, after having provided significant support to the development of ISO/IWA 15. Her standards development expertise is further applied in handling the balloting process of ISO and ASTM standards for the relevant technical committees in the US.
Key Roles:
– ISO/TC48/WG05 – Secretary
– ANSI US TAG to ISO/TC48 – Vice Chair
Responsible for:
– FDA regulations
– ISO 9001 certification
– ISO 17025 accreditation
– Internal audits
– Compliance to RoHS, REACH, TSCA, and others
Richard has been applying his scientific expertise to the development of international standards for over 25 years. He proposed and authored ISO 8655-7:2005 and ISO/TR 16153, based on the ratiometric photometric method for volume determination.
He was an active member in the ASTM International (formerly American Society for Testing and Materials) committee on laboratory apparatus, as well as in NCSL International (formerly National Conference of Standards Laboratories) through the 1990’s. In 1995, he became involved in the revision of DIN 12650 series of standards related to pipettes and other piston-operated apparatus, which led to the development of the ISO 8655 series of standards.
The co-founder of Artel, Richard was company’s original member delegate to the NCSLI – an international metrology association founded at the request of the US National Institute of Standards and Technology (NIST). This close engagement with metrology and measurement excellence was formative in the development of Artel’s measuring systems and laboratory capabilities.
He authored numerous papers and presentations on the topic of pipette calibration, which are referenced in compliance standards, such as the checklists issued by CAP (College of American Pathologists).
Key Roles:
Author of:
– ISO 8655-7:2005
– ISO/TR 16153:2004
– Performance verification of manual action pipettes, Am Clin Lab 1994
– Referenced in CLSI GP-31 A
– Referenced in CAP checklists
– NCLSI member delegate and appointing officer
– ASTM E41 member since mid-1990’s
George has been engaged in international standards and metrology for more than 20 years – working with colleagues at ISO, ASTM International (formerly the American Society for Testing and Materials), CLSI, and NCSL International (formerly the National Conference of Standards Laboratories).
He chairs the ISO working group responsible for the development of the new standard for Automated Liquid Handling Systems, after having co-proposed and chaired the development of ISO/IWA 15, which was published in 2015. He is the former chair of the ISO working group responsible for pipettes and other piston-operated apparatus, where he proposed the development of a new ISO standard for the “Photometric Reference Measurement Procedure for the Determination of Volume” (ISO 8655-8). George is also a technical expert in the revision of all parts of the ISO 8655 series of standards and proposed the development of the new ISO standard on Operator Training and Pipetting Technique.
His deep expertise in metrology is applied in the current revision of the ISO technical report on the estimation of uncertainty for the photometric reference method, numerous articles, as well as across Artel’s product line.
Serving as chair of the US technical advisory group to the ISO technical committee responsible for laboratory equipment, George is responsible for achieving consensus among US experts and articulating this US consensus positions the ISO international technical committee.
George chairs the ASTM sub-committee on laboratory apparatus and serves as secretary to the parent main committee. His metrology expertise was applied in the revision of the balance calibration standards ASTM E898 and E617, which is referenced in the USP (United States Pharmacopeia).
He co-authored the chapters about pipettes and liquid handling processes in the current edition of CSLI QMS-23.
Key Roles:
– Co-author of:
– ISO 8655-7
– ISO 8655-8
– ISO/TR 16153
– Proposer of ISO/IWA 15
– Proposer of ISO 23783-1, -2, -3
– CLSI QMS-23 – Contributing Author
– ISO/TC48/WG05 – Convenor
– ISO/TC48/WG04 – Former Convenor
– ASTM E41 – Secretary
– ASTM E41.06 – Chair
– ASTM E898:2020 – Revision Participant
– ASTM E617:2018 – Revision Participant
– ASTM E1154 – Technical Contact
– ANSI
– US TAG to ISO/TC48 (Laboratoy Equipment) – Chair
– ANSI International Forum – Participant
– NCLSI – Member Delegate & Healthcare Metrology Committee
Kathleen extends Artel’s commitment to using innovative processes for error-free results to Artel’s finance-related activities. Responsible for financial planning and analysis, evaluating strategic opportunities, budgeting, benefits, and compensation, Kathleen uses her long history of doing mergers and acquisitions from a consulting and business side to bring analytical excellence to strategic evaluations, and her experiences at larger companies to advance established processes.
When not at Artel, Kathleen uses all her experience in efficiency and productivity to care for her two daughters and their cat, dog, and horse and, in the very little time left over after that, enjoys travelling to other countries, meeting new people and learning about other cultures.
“Live life as if you were to die tomorrow. Learn as if you were to live forever.” Mahatma Gandhi
Bernadette is the driving force (and friendly face) behind Artel’s content-heavy and customer-centric approach to marketing. She develops marketing/branding strategies and communications campaigns, and leads program execution and analysis by coordinating internal and external efforts, managing budgets, and ensuring consistency and adherence to Artel’s high standards.
Bernie’s strength lies in her ability to reach across all disciplines at Artel—scientific, engineering, metrology, technical support, product development, production, sales, and field support—to make sure that customers are getting the valuable information they need.
Bernie’s passion for detail, quality, and authentic content is expressed in her extraordinary culinary skills, whether the cooking is for an (extensive) family gathering or making a meal for the local community teen center.
“What people do with food is an act that reveals how they construe the world.” Marcella Hazan
John keeps one eye on the latest technologies and another on the challenges facing today’s life science labs. He and his team of eagerly engaged scientists and engineers test new ideas to enhance Artel’s current products and build out tomorrow’s solutions.
Like many Artelians, John is driven by a lifelong curiosity in the physical world around him. He has turned his fascination with spectroscopy and understanding how light interacts with molecules into products that solve real-world productivity and quality challenges for scientists. He was part of the original team that created the MVS and has been involved in product development at Artel since he walked through the front door.
Descended from a family whose motto is probably best expressed as “do a job right, do it completely, and don’t let go until it’s done,” John embodies this philosophy during the day at Artel. He propagates that motto to his kids through gardening, tapping Maple trees and exploring the great backwoods and waterways of Maine.
“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.” – something Mark Twain may, or may not, have said…probably
Wendy puts her years of experience in the laboratory and her passion for helping people and problem solving to good use as Artel’s Technical Services Manager. Her background has given her hands-on knowledge of customers’ tests and assays, enabling her to understand their pain points since she has experienced them herself. Her goal is to ensure that first-class service is provided by Artel’s customer-facing team, whether it’s directly interacting with customers or through her management of the team. Through hiring, training and guiding her team, she nurtures productive, long-lasting customer relationships.
Wendy’s focus on customers also makes her an excellent internal customer representative to Artel’s teams, where she provides input on product development to the R&D team and communicates any quality issues with Artel products and services to the operations team.
Wendy’s drive to help others resolve problems is not limited to Artel but is evident in all aspects of her life, especially with her children. When not assisting customers, Wendy likes to stay active by biking, boating, and taking long walks in beautiful Maine.
“Nobody cares how much you know until they know how much you care.” commonly attributed to Theodore Roosevelt
Richard combines his scientific education, love of learning, curiosity, and passion for making things work better to build products that help life science labs meet quality and productivity goals. His favorite challenge is finding the bullseye at the intersection of corporate strategy, market need and available technology, and then figuring out how to create a product which hits that target. His leadership has been instrumental in shaping Artel’s products and services into the effective, easy-to-use, and quality-focused offerings that they are today.
When not creating tools and knowledge to help life science labs get the right answers every time, Richard enjoys the great Maine outdoors—canoeing, camping, and gardening—as well as woodworking (usually in the great Maine indoors).
“When you have eliminated every possibility for inaccuracy, then accuracy remains your only option.”
With years of pharmaceutical industry experience centered around analytical chemistry, automation, and new technologies, as well as a background in teaching assay development and validation, Nat’s a natural in his role at Artel as the primary driver and chief communicator of product applications. From optimizing assays, processes, and workflows to pipette user training and calibration, Nat communicates to customers how Artel products and services can improve quality and productivity.
At the same time, he keeps track of key assay trends and applications to inform new product development and strategic guidance for business development, partnering, and collaborative opportunities.
While typically a casual and friendly person at Artel and at home, Nat’s aggressive commitment to quality comes out when he homebrews beer and other fermented beverages and he’s even been known to kick people out of the kitchen to avoid contamination.
“Fast is fine but accuracy is everything.” Wyatt Earp
As a co-founder and President, Kirby’s role at Artel is similar to that of an orchestra conductor—he melds the different elements of the company into a powerful whole, bringing out the best in his colleagues and creating synergies that together overcome customer challenges in liquid handling, quality, and regulatory compliance.
Through a combination of curiosity and discipline, creativity and precision, he works with his fellow Artelians to build outside-the-box solutions that are efficient, easy-to-use, highly effective and based on science. Their goal: to ensure that each customer finds new opportunities and executes new solutions to achieve productivity and compliance objectives.
When not at Artel, Kirby takes up his own instruments, the saxophone and piano, playing for the approval of Charlie Parker and Gabriel Faure.
“Music is your own experience, your thoughts, your wisdom. Master your instrument, master the music. If you don’t live it, it won’t come out of your horn.” Charlie Parker
As the Production Manager, Jim maximizes Artel’s productivity and quality by ensuring that all supplies and components are in place, providing proper training for production personnel, maintaining effective processes, and supporting an overall positive, sound and safe working environment.
Driven by a desire to help others, Jim uses his 30-plus years of experience in the photometric instrument field to ensure that customers know they can rely on Artel, answering questions, solving problems, and guiding them through to complete resolution of any issues they have with their lab’s systems.
Like many at Artel, Jim enjoys cooking and home renovation, and is currently combining his helpfulness and home renovation skills by working on his daughter and son-in-law’s house.
“Seek first to understand, then to be understood.” Stephen R. Covey
An important part of building high-quality products, and providing services that rely on those products, is ensuring that the components and supplies are also high-quality and readily available. Which is why Jack focuses on keeping supply-side relationships top notch. Responsible for the extended supply chain—procurement, purchasing, inventory control, warehousing, shipping, and trade compliance—as well as Artel’s facilities and physical plant, Jack ensures quality by being both a good customer and delivering good customer service.
Jack’s adherence to high standards, quality, and attention to detail are a great fit for his work at Artel and can also be seen in the years-long home renovation project he and his wife have been undertaking. When not at Artel, Jack is an avid traveller, gardener, and connoisseur of cinema and literature.
“No one knows the cost of a defective product – don’t tell me you do. You know the cost of replacing it, but not the cost of a dissatisfied customer.” W. Edwards Deming
Officially, Graham is responsible for overseeing sales, strategic marketing, business development, and applications of Artel’s technology. In practice, this means listening to customers and leveraging his broadly eclectic scientific and business background to identify technological solutions that improve data quality and productivity.
Initially trained as a molecular biologist/protein biochemist, his many years troubleshooting misbehaving assays and analytical methods make him particularly well-suited to a role helping customers with their data quality. The many years at the bench have given Graham a deep appreciation of the importance of reducing sources of noise and variability which, together with experimental controls, can help save weeks and even months of wasted time.
When not at work, Graham’s total embrace of the experimentalist’s spirit is evident in his approach to cooking and baking, also known as “the experiment you get to eat,” which requires precision and tight QC of the ingredients as well as exact execution of the recipe steps to get the desired tasty outcome.
“I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.” Lord Kelvin
With a specialization in metrology and a lifelong interest in both science and engineering, George is ideally suited for his role as Artel’s representative to metrology and standards organizations, laboratory accreditation bodies, and government regulators, where he helps shape regulatory frameworks around liquid handling processes.
These activities give George a deep understanding of regulatory compliance which, coupled with his metrology and quality expertise, he uses to help customers improve data quality and efficiency while maintaining regulatory compliance. This help is especially critical for customers making process improvements, as change can be challenging in regulated environments.
George’s interest in metrology and standards extends beyond his work at Artel (see how he celebrated World Standards Day in 2016). For example, in George’s words, “Deflategate could have been avoided with a properly defined and validated measurement process. With no stated reference temperature, the NFL cannot possibly regulate ball pressure to plus or minus 0.5 psi. A game of inches and seconds, $15 billion annual revenue, and zero metrologists!”
“Every system is perfectly designed to get the results it gets.” Often attributed to W. Edwards Deming, but more likely from Paul Batalden.
As the person in charge of Artel’s Quality Management System, Cary plays a critical role in making sure that Artel’s commitment to quality is always being met. By training employees and keeping all quality processes and procedures well-documented and up-to-date with current regulatory standards she ensures regulatory compliance, and by assessing and evaluating performance both internally and externally (Suppliers) and customer feedback, she supports overall productivity and effectiveness to ensure we meet our customers’ expectations.
When not working closely with her team members to maintain Artel’s quality management processes, Cary enjoys the peace found hiking in the beautiful Maine outdoors.
“Nature does not hurry, yet everything is accomplished.” Lao Tzu
“Random is not one of my strengths.” Doreen Rumery
With a strong work ethic, thorough attention to detail, inquisitive mind that needs to know why things work (or don’t work), and passion for standardization, Doreen is exactly the right kind of person to manage Artel’s chemistry and calibration labs. She’s responsible for making sure the labs run smoothly, ensuring product and instrument quality, calibrations, regulatory compliance, lab personnel training, timely delivery of products, troubleshooting, and process improvements.
Doreen’s need for standardization is apparent even in her home life where spreadsheets and planning tools are used to ensure the household runs smoothly. When not at Artel, Doreen likes to spend time with her family (some of whom she also sees at Artel), gardening, and travelling with her many sisters and brother.
“Quality is never an accident; it is always the result of high intention, sincere effort, intelligent direction and skilful execution; it represents the wise choice of many alternatives.” William A. Foster
Table 1. Regulations that require demonstration of pipette competency training and/or assessment
ISO Standards | |
ISO/IEC 17025:2005 | General Requirements for the Competence of Testing and Calibration Laboratories |
ISO 15189:201 | Medical Laboratories; Requirements for Quality and Competence |
ISO 15195:2003 | Laboratory Medicine; Requirements for Reference Measurement Laboratories |
FDA cGMP regulations (current Good Manufacturing Practice) | |
21 CFR Part 211 | cGMP for Finished Pharmaceuticals |
21 CFR Part 225 | cGMP for Medicated Feeds |
21 CFR Part 820 | Quality System Regulation for Finished Devices for Human Use |
21 CFR Part 1271 | Human Cells, Tissues, and Cellular and Tissue-based Products |
GLP (Good Laboratory Practice) | |
FDA: 21 CFR Part 58 | GLP for Non-clinical Laboratory Studies |
EU: Directive 2004/10/EC | Principles of Good Laboratory Practice 1997 (Part 1), from the Organisation for Economic Cooperation and Development (OECD) |
GCP (Good Clinical Practice): | |
International Conference on Harmonization (ICH) E6 | Good Clinical Practice – Consolidated Guidance 1996 |