Question

Being careful not to disturb the cell pellet at the bottom, decant the supernatant from each centrifuge tube using a different sterile transfer pipette.

Short answer

Decant the supernatant carefully with a sterile pipette to avoid disturbing the pellet.

Step-by-step solution

Prepare the Workspace

Ensure that the workspace is clean and all necessary materials, such as centrifuge tubes and sterile transfer pipettes, are ready and accessible.

Identify the Supernatant and Pellet

Carefully observe the centrifuge tube. Identify the liquid portion, known as the supernatant, at the top and the solid cell pellet at the bottom.

Position the Pipette

Take a sterile transfer pipette and position it near the top of the supernatant, being careful not to touch the pellet at the bottom.

Decant the Supernatant

Slowly and carefully decant the supernatant by drawing the liquid up into the pipette. Ensure that the pellet remains undisturbed.

Transfer the Supernatant

Use the pipette to transfer the supernatant to a new container, ensuring that the transfer process is done gently to avoid disturbing the pellet.

Use Different Pipettes

Repeat the decanting process for each centrifuge tube, using a different sterile transfer pipette for every tube to prevent cross-contamination.

Key concepts

Understanding the Cell Pellet

The cell pellet forms at the bottom of the centrifuge tube after it has been spun at high speed. It contains solid materials, like cells or debris, that have been separated from the liquid above. This process happens because the centrifugal force pushes heavier particles down, creating a distinct layer.
To ensure the success of your experiment, it is crucial to avoid disturbing the cell pellet when performing procedures involving the supernatant. Disturbing the pellet can mix the solid material back into the liquid, altering the intended separation.
When working with cell pellets:

• Be gentle when repositioning the tube.
• Keep the tube upright to prevent the pellet from spreading.
• Use appropriate tools to handle the tube and materials.

Decanting the Supernatant

The supernatant is the liquid portion found at the top of the centrifuge tube, separated from the cell pellet. Proper decanting of the supernatant is essential to maintain the integrity of the separated materials.
Here’s how to decant without disturbing the pellet:

• Visually locate the supernatant at the top of the tube.
• Position your sterile transfer pipette near the top, avoiding the cell pellet.
• Suck up the liquid slowly and carefully.

This process ensures that you are only removing the supernatant, leaving the pellet intact at the bottom.
Decanting gently ensures that no solid particles are mixed back into the supernatant.

Using a Sterile Transfer Pipette

Sterile transfer pipettes are vital tools in laboratory settings. They ensure precise liquid handling while maintaining sterility to prevent contamination.
When using sterile transfer pipettes:

• Always use a new pipette for each sample to avoid cross-contamination.
• Handle the pipette by its upper part to maintain its sterility.
• Dispose of the pipette properly after single-use.

Using sterile pipettes effectively ensures the purity of samples and the accuracy of the experiment.

Avoiding Cross-Contamination

Cross-contamination occurs when unwanted substances from one sample mix with another, potentially skewing experimental results.
To prevent cross-contamination:

• Always use a new sterile transfer pipette for each tube.
• Keep the workspace clean and organized.
• Regularly disinfect tools and surfaces.

By adhering to these practices, you maintain the integrity of your samples and the reliability of your experimental results.