The value of scientific research rests in its accuracy, reliability, and repeatability. In many cases, that translates to valid measurements captured through pipetting vast volumes of liquids. These efforts require high precision, but they're also vulnerable to avoidable error. These errors can be avoided with careful use of liquid handling best practices.
Learn more about correct pipetting, the value of automation, the benefits of sophisticated equipment, and mistakes to avoid.
What Are the Protocols for Liquid Handling?
The reliability of your pipetting results largely comes down to human skill — and fallibility. You can minimize your errors by following these guidance tips for pipetting:
- Select the right pipette: Generally, pipetting should be done at 35-100% of the pipette's nominal volume. For example, when pipetting 100uL, it's better to opt for a 10-100 µL pipette rather than 100-1000 µL. In other words, you want to choose a pipette with the smallest volume range for your needs.
- Monitor temperature: Temperature impacts liquid volume. Pipette at a constant temperature between 20° and 25°C for greatest accuracy.
- Use proper technique: Hold the pipette vertically, aspirate near the liquid surface, wait one second before lifting the pipette, and dispense slowly.
- Pre-wet: For volumes over 10 µL, pre-wet the pipette tip for better accuracy.
- Change tips: Switch tips when changing liquids to avoid cross-contamination. Changing tips can reduce errors by 4%.
- Store pipettes vertically on stand: When leaving a pipette flat on the bench, liquid left in it could enter internal parts, leading to corrosion. Hand warmth can affect thermal equilibrium and sample volume.
- Clean and calibrate frequently: Always clean external pipette surfaces with isopropyl alcohol and calibrate them at least once a year to ensure consistent measurements.
Liquid Handling Best Practices
It isn't uncommon for lab staff to pipette for more than two hours at a time while conducting research. However, engaging in this repetitive activity can lead to negative consequences. In fact, the risk for hand and shoulder injuries, often called repetitive strain injuries (RSIs), increases after 1.5 hours of continuous pipetting.
Alongside limiting how long you pipette in a single session, following these ergonomic liquid handling best practices can lead to consistently better results:
- Work with your hands below shoulder height. Avoid working in uncomfortable positions, such as in a biosafety cabinet.
- Hold your wrist in a neutral position and avoid equipment that requires you to extend or rotate your wrist or elbow unnecessarily.
- Keep everything within the forearm's reach. Constantly reaching for necessary equipment can overstress the tendon in your elbow.
- Don't rest your elbow on a hard surface. It can cause numbness and tingling in your hand or an ache inside your elbow.
- Adjust your sitting position so it's comfortable with the height of your lab bench.
In addition, frequently switch between pipetting and other activities, and switch your hands to avoid hand exhaustion. Every 30 minutes, try to take a break to get up and move around.
The Benefits of Liquid Handling Automation
Historically, most pipetting has been completed manually. However, automated systems, like the Corning® Lambda™ EliteMax Semi-Automated Benchtop Pipettor, offer multiple benefits:
- Saves time: Versatile platforms can pipette multiple rows and columns and may be customized by liquid type. They can be programmed to run serial dilutions, tube-to-tube transfers, and plate replications, freeing staff for other, higher-priority responsibilities.
- Boosts productivity: Automated pipetting is faster than manual pipetting. The increased throughput improves efficiency. Automated systems can handle setups between 1 µL and 20 µL.
- Improves safety: Manual pipetting carries higher risks for RSIs and mistakes. Automated systems reduce errors. They can work inside biosafety cabinets, improving staff safety.
- Enhances accuracy: Precise pipetting dispenses the same volume each time, improving data quality.
Pipetting Solutions
Corning has a wide product selection dedicated to accurate, reliable pipetting. This equipment offers several ergonomic features that support liquid handling best practices, including:
- Comfortable handle shapes to decrease effort and potential injury.
- Finger hooks and contoured shapes for relaxed grips.
- Lighter weight to limit hand fatigue.
- Low pipetting and tip ejection forces to reduce RSIs.
For transferring large volumes, we recommend using a bottle top dispenser that works with most Corning plastic and glass bottles. This precision device is a universal solution for dispensing organic and inorganic liquids. It offers quick, accurate volume settings and a three-position discharge tube (dispensing, sample recovery, and emptying). It also has a 360° rotatable valve block for easy, accurate dispensing.
Common Mistakes with Liquid Handling
Even when using the most advanced pipetting equipment, there are still several mistakes to avoid ensuring you follow liquid handling best practices. These include:
- Not assessing liquid viscosity: Denser liquids dispense slowly, but thinner ones dispense quickly and can evaporate.
- Dispensing too quickly: Rapid pipetting can lead to volume errors and contamination.
- Reusing pipette tips: Reusing the same pipette tip to extract and dispense different liquid samples can promote contamination.
- Disregarding pipette maintenance: Improper maintenance can cause volume measurement errors and contamination. Daily cleaning is essential.
- Ignoring calibration: At a minimum, calibrate your pipettes once a year. Calibration every three months is ideal to ensure accuracy.
- Using the wrong angle: Aspirate from 90° and dispense from 45°.
- Aspirating air: Taking air into the pipette can introduce it into the pipette neck and create inaccurate volumes.
- Immersing pipette tip too deep: Always aspirate liquid from the surface of the sample, being careful not to suck up air.
- Storing pipettes incorrectly: Always store pipettes vertically to prevent contamination or corrosion.
- Using the wrong tip: Choose the right-sized tip for your pipette to ensure accuracy and decrease contamination and air aspiration.
- Not pre-wetting tips: Moistening tips minimizes liquid evaporation. Pre-wetting is recommended for volumes over 10 µL.
- Ignoring temperature: Temperature can change liquid volumes. Pipette at room temperature to ensure greater accuracy.
Accurate, reliable pipetting that supports reproducible results is a critical component of high-value scientific research. With these liquid handling best practices, you can enhance the quality of repeated investigations.