Analysis of Abnormal Pipetting Volumes in Pipettors

Accurate and precise pipetting is a cornerstone of laboratory work, ensuring reliable results in various scientific applications. However, there are instances when pipetting volumes deviate from the expected values, leading to both frustration and potential inaccuracies. In this article, we will delve into the analysis of abnormal pipetting volumes in pipettors, exploring the possible causes and systematic steps to diagnose and resolve such issues. Whether you're a seasoned researcher or a newcomer to the lab, understanding these troubleshooting techniques can greatly enhance your pipetting experience and contribute to the integrity of your experimental outcomes.

1. Excessive Pipetting Volume

Instances of excessive pipetting volume are relatively rare. If encountered, there are generally two reasons:

• Operational Error: This occurs when the aspirate/dispense button is pressed all the way down while pipetting, when it should actually be pressed to the stopping point (not fully depressed).

• Pipettor Calibration Issue: The pipettor might require calibration using appropriate tools to adjust the volume setting.
  
  

2. Insufficient Pipetting Volume

Insufficient pipetting volume is a common issue and can be caused by several factors. Here's a systematic approach to diagnose and solve the problem:

• Check Pipette Tips: Examine whether the pipette tip is properly attached and if it's deformed. You can also try using a new, visually undamaged tip to see if the problem persists. If the pipetting volume remains insufficient, proceed to the next step.

• Inspect the Shaft: Check the shaft's surface where it connects with the pipette tip. If there are minor scratches due to prolonged friction or if the surface feels rough, consider replacing the shaft. Also, ensure the shaft isn't blocked. Detach the shaft and hold it with the wider end toward your eye and the narrower end toward a light source. If you can't see light passing through, the shaft is blocked. Use a thin metal wire to clear the blockage. Once you've confirmed the shaft is fine, check if the pipetting volume is still insufficient. If the problem persists, move to the next step.

• Check Pipettor's Seal: Set the pipettor's volume range to the maximum and attach a tip. For pipettors with a volume range of 200 μl and above:

  • Pipette water and hold it vertically for 15 seconds. Check if any water droplets form or fall from the tip. If no change is observed, the seal is good.

• For pipettors with a volume range below 200 μl:

  • Pipette water and keep the tip submerged in the water for 15 seconds. Observe if the liquid level inside the tip drops. If there's no drop, the seal is good.

• If the pipettor's seal is confirmed to be intact but the pipetting volume is still insufficient, contact the supplier for adjusting the volume setting using appropriate tools. If the seal isn't intact, proceed to the next step.

• Inspect the Piston System: Remove the piston and check for contamination. Clean the piston and apply lubricating oil before reassembling it. Check if the pipetting volume is now correct. If the problem persists, involve the supplier for further resolution.

• For more severe issues such as aging seals or rusted pistons, contact the supplier for assistance.

In summary, troubleshooting abnormal pipetting volumes involves a systematic approach. Begin with simple checks, progressing to more complex steps, and involving the supplier if necessary to ensure accurate and reliable pipetting results.