How to Improve Your Pipetting Technique?
How good is your manual pipetting technique?
With increasing demands for accuracy, precision, and sustainability in laboratories, it becomes crucial to comprehend and refine your manual pipetting technique.
That is why we prepared a short list of 12 steps on how to improve your technique to enhance your pipetting proficiency and determine which ones you have already mastered and incorporated into your daily routine.
Pre-wet the pipette tip before use
Pre-wet the pipette tip by aspirating and expelling liquid at least three times before delivering a sample. This minimizes evaporation within the tip, ensuring more accurate sample volumes, especially crucial when handling volatile samples like organic solvents.
Dip the tip to the correct depth when aspirating
Before aspirating, ensure the tip is immersed appropriately below the meniscus. For large volume pipettes (1–5 mL), immerse to 5–6 mm, and for smaller volumes, immerse to 2–3 mm. Insufficient immersion, especially with larger pipettes, may result in air aspiration, while excessive immersion can cause sample adherence to the outer tip. Avoid touching the container’s bottom, as it can impede aspiration.
Consistently pause after aspirating
Allow the tip to remain in the liquid for about one second after aspirating the sample. This brief pause allows the liquid in the tip to settle after the plunger stops, ensuring accurate volume delivery. Maintain consistency in these pauses for optimal results.
Maintain a consistent plunger pressure and speed
Depress and release the plunger smoothly and consistently, applying uniform pressure and speed during both aspiration and dispensing of each sample. Consistent actions yield reliable results.
Pull out the pipette straight
When aspirating, keep the pipette vertical, avoiding container sides. For withdrawal after aspiration, pull the pipette straight from the center, crucial for small volumes (<50 µL). Tilting or touching container sides can alter aspirated volumes, causing wicking and volume loss due to surface tension.
Inspect the tip before dispensing the sample
Before dispensing, use a lint-free cloth to gently remove any droplets on the outside of the tip, ensuring not to touch the tip opening. Absorbent materials near the opening can quickly draw out the sample, and excessive wiping increases the risk of sample loss. Exercise caution during this process.
Inspect the tip after dispensing a sample
When dispensing a sample, touch the tip to the container side to release any residual liquid. Maintain thumb pressure on the second stop of the plunger, and remove the tip promptly to prevent sample re-aspiration. Ensure visibility of the sample leaving the tip.
Use standard mode pipetting
Use “standard (or forward) mode” pipetting for aqueous samples. Choose “reverse mode” rather than viscous or volatile samples. Utilizing reverse pipetting with standard aqueous samples can lead to over-delivery, while employing standard mode with viscous or volatile samples may result in under-delivery.
Select the appropriate pipette
Use a pipette with a volume range closest to the intended aspiration and dispensing volume. Improved accuracy is achieved when there is a slight difference between the pipette’s minimum volume and the tested volume. For instance, if dispensing 15 µL, a 1 mL pipette would be inappropriate, while a 20 µL pipette would be ideal.
Select the correct pipette tip
Choose high-quality tips designed for specific pipettes; manufacturer-recommended tips are generally reliable. If proven with a particular pipette model, alternative brands are acceptable. Mismatched tips and pipettes can cause inaccuracy or imprecision. Quality tips create an airtight seal effortlessly, made from superior materials, free of molding defects, ensuring dependable liquid delivery.
Operate at room temperature equilibrium
Let liquids and equipment equilibrate to room temperature before pipetting. Air displacement pipette accuracy is influenced by temperature-related factors like air pressure, humidity, and liquid vapor pressure. Consistent temperature minimizes variations, enhancing overall precision.
Reduce pipette handling
Gently hold the pipette, place it back on the stand when not in use, and wear gloves to minimize body heat transfer. Avoid touching pipette tips or containers of yet-to-be-pipetted samples. Body heat interference can disrupt temperature equilibrium, causing variations in delivered volumes.
Visit this website to download the infographic, featuring illustrative examples of all these tips. Share it with your colleagues, or print it for your lab.
