Volumetric Pipets: Usage and Calibration

Introduction

• Volumetric pipets are glass or plastic tubes used for accurate liquid measurements.
• They typically range from 1 to 100 ml in volume.
• Calibrated to deliver specific volumes, with specifications imprinted on the pipet.

Specifications

• Calibration Line: Indicates how much liquid will be delivered if drawn to this line.
• Temperature: Calibration is specific to a certain temperature.
• TD vs. TC Pipets:
  • TD (To Deliver): Calibrated to deliver the specified volume.
  • TC (To Contain): Calibrated to contain the specified volume, with no remainders.

Preparation

1. Inspect Pipet: Ensure cleanliness. If water beads inside, clean or replace the pipet.

Rinsing Procedure

• Pour Liquid: Use a beaker to hold the liquid to be pipetted.
• Rinse: Draw up a small quantity of liquid and rinse the interior surface.
  • Roll the pipet horizontally with a slight rocking motion.
  • Drain rinse liquid into a waste beaker.
  • Repeat at least two more times.

Pipetting Procedure

1. Fill the Pipet:
   • Use a pipet bulb to draw liquid above the graduation mark.
   • Ensure no air bubbles or foam.
   • Wipe the outside with a lint-free tissue.
2. Set the Meniscus:
   • Hold pipet vertically and align the bottom of the meniscus with the graduation mark.
   • Keep the mark at eye level.
3. Deliver the Liquid:
   • Move to the receiving vessel, keeping the pipet vertical.
   • Allow liquid to drain naturally.
   • Leave pipet tip touching the vessel wall for an extra 5 seconds.

Important Tips

• Do not blow or shake out the remaining liquid in the tip.
• The pipet is calibrated to account for the small liquid remainder.

Summary of Steps

• Inspect and rinse pipet.
• Use a pipet bulb to fill above the mark.
• Wipe pipet and set meniscus.
• Drain liquid into receiving vessel, maintaining contact with the vessel wall for additional time.