Start by selecting the pipette appropriate for your volume.

Dr. Smith: ‘This is correct!’ She proceeds to demonstrate the correct procedure.

1. Select the Appropriate Pipette: Choose a pipette that matches the volume range required for your task.

2. Attach a Pipette Tip: Firmly attach an appropriate, sterile tip to the pipette. Ensure it fits snugly to avoid leaks.

3. Set the Desired Volume: Adjust the pipette to the required volume using the volume adjustment dial. Ensure it locks in place.

4. Aspiration:

• Press the plunger to the first stop (the initial resistance point).

• Immerse the tip vertically just below the surface of the liquid to be aspirated.

• Release the plunger slowly and steadily to aspirate the desired liquid volume.

5. Dispensing:

• Align the tip with the receiving vessel and press the plunger to the first stop to dispense the liquid.

• Press the plunger to the second stop to expel any remaining liquid in the tip.

6. Dispose of the Tip: Eject the used tip into a waste container using the tip ejector button, being careful not to touch the tip with your hands.

7. Repeat as Necessary: If more repetitions are needed, attach a new tip and repeat the process.

For a more extensive video visit this link: How to pipette correctly – a short step-by-step introduction into proper pipetting (https://www.youtube.com/watch?v=QGX490kuKjg) 

Dr. Smith instructs the students to pipette 1000 μL and watches Emma's careful attempt noting her frustration with the small droplets lingering in the tip.

What is the most likely error? 

Option 1: Emma is likely releasing the plunger too quickly during aspiration, which can cause air bubbles to form in the tip and lead to inconsistent volume uptake (e.g 1050 μL).

Option 2: Emma is likely submerging the pipette tip too deeply, causing liquid to be drawn into the tip due to increased pressure differences or capillary action. 

Option 3: Emma is holding the pipette at an incorrect angle (rather than vertically) while aspirating or dispensing can lead to incorrect volume measurements.