How to use a Volumetric Pipette - Science@Waikato

Summary

This instructional video demonstrates the proper use of a volumetric pipette, a tool for measuring precise volumes of liquid. It explains the significance of pipette sizes and volume units, and emphasizes the importance of avoiding contamination by transferring solutions from a beaker rather than directly from a bottle. The video illustrates how to use a pipette filler to draw up a solution to the correct meniscus level, ensuring accuracy by adjusting to the line at eye level. It also covers the technique for dispensing the solution into a flask, highlighting the need to allow the solution to fully drain without shaking out residual liquid, as the pipette is calibrated to account for this.

Takeaways

• 🔍 A volumetric pipette is used to measure out an exact volume of liquid.
• 📏 Volumetric pipettes come in various sizes and are marked with volume units, which can be in milliliters or cubic centimeters.
• 🌡️ When drawing liquid into the pipette, it's crucial to do so at eye level to ensure accuracy.
• 🚫 Avoid pipetting directly from the stock solution bottle to prevent contamination; instead, use a beaker.
• 🔧 A pipette filler is a common device used to fill volumetric pipettes, reducing the risk of breakage.
• ✋ When inserting the pipette into the filler, hold it near the top to avoid damage.
• 💧 Use the scroll wheel on the pipette filler to draw the solution up into the pipette, initially drawing past the calibration line.
• 🔽 Adjust the scroll wheel to lower the meniscus to the exact calibration line after drawing the solution past it.
• 🧪 Transfer the filled pipette to a flask and use the button on the filler to dispense the solution.
• ⏳ Allow the solution to drain completely from the pipette, which may take a few moments.

Q & A

What is the purpose of a volumetric pipette?

A volumetric pipette is used to measure out an exact volume of liquid.

What are the different sizes of volumetric pipettes, and how are they labeled?

Volumetric pipettes come in various sizes and are labeled with the volumes on the sides, with units shown in either milliliters or cubic centimeters.

Why are milliliters and cubic centimeters considered equivalent in this context?

In the context of volumetric pipettes, milliliters and cubic centimeters are considered equivalent because they both measure volume and are used interchangeably for labeling the pipette sizes.

How should you draw a solution into the volumetric pipette?

You should use a pipette filler to draw a solution up until the meniscus touches the line on the pipette, ensuring this is done at eye level.

Why is it important to avoid pipetting directly from the stock solution bottle?

Pipetting directly from the stock solution bottle might introduce contamination, so it's better to pour the solution into a beaker and pipette from there.

What is the proper way to fill a volumetric pipette using a pipette filler?

Insert the pipette into the filler holding it near the top to avoid breaking it, and ensure it fits tightly. Then, use the scroll wheel to draw the solution up into the pipette.

How do you adjust the meniscus to the calibration line on the pipette?

After drawing the solution past the line on the pipette using the pipette filler, use the scroll wheel to lower the meniscus to the exact line.

What is the correct technique for dispensing the solution from the volumetric pipette?

Transfer the pipette to a flask and push the button on the side of the filler to dispense the solution, allowing all of it to drain from the pipette.

Why should you hold the tip of the pipette to the side of the flask when dispensing?

Holding the tip of the pipette to the side of the flask ensures that all of the solution is dispensed without splashing or contamination.

What should you do with the small amount of solution left in the tip of the pipette after dispensing?

Do not try to shake it out, as the pipette has been calibrated to account for the small amount of solution left in the tip.