Pre-lab talk Pipetting Volume Ranges and Compatible Tips Each micropipette requires a specific type of tip to ensure accurate measurements: • P2: 0.2–2 µL, small yellow tips • P10: 1–10 µL, small yellow tips • P20: 2–20 µL, small yellow tips • P200: 20–200 µL, small yellow tips • P1000: 100–1000 µL, large blue tips Always verify that the tip fits snugly to prevent leaks and ensure precision. Using the wrong tip (e.g., small yellow tips for a P1000) can lead to errors and imprecise measurements. Steps for Using a Micropipette 1. Select the Correct Micropipette and Tip: Choose the pipette and its corresponding tip based on the desired volume. • For 50 µL, use a P200 with a small yellow tip. • For 750 µL, use a P1000 with a large blue tip. 2. Set the Volume: Rotate the dial to the desired volume. Example settings: • P200: Set to 1-0-0 for 100 µL. • P1000: Set to 0-7-5 for 750 µL. 3. Attach the Tip: Firmly press the micropipette onto the tip to create an airtight seal. 4. Aspirate Liquid: • Press the plunger to the first stop. • Submerge the tip just below the liquid surface. • Release the plunger slowly to aspirate the liquid. 5. Dispense Liquid: • Touch the tip to the side of the receiving container. • Press the plunger to the second stop to expel all liquid. 6. Eject the Tip: Use the tip ejector button to discard the tip into a waste container. 1 Common Errors and Troubleshooting • Incorrect Tip Usage: Using a small yellow tip with a P1000 will lead to inaccurate measurements. Always use a large blue tip for a P1000. • Fast Plunger Movement: Pressing or releasing the plunger too quickly can cause air bubbles and inaccurate readings. • Setting Volume Outside Range: Setting a P200 to 250 µL exceeds its maximum range and may damage the pipette. 2 Practice Problems Problem 1: You need to measure 200 µL. Which micropipette and tip should you use, and what settings are required? Answer: Use a P200 micropipette with a small yellow tip. Set the dial to 2-0-0. Alternatively, you can use a P1000 with a large blue tip and set the dial to 0-2-0. Problem 2: You need to measure 50 µL. Which pipette and tip should you use, and what are the settings? Answer: Use a P200 micropipette with a small yellow tip. Set the dial to 0-5-0. You can also use a P1000 with a large blue tip, but set the dial to 0-0-5. Problem 3: You need to transfer 750 µL. Which pipette and tip are required, and how should you set the volume? Answer: Use a P1000 micropipette with a large blue tip. Set the dial to 0-7-5. A P200 cannot be used because it exceeds its maximum range. Problem 4: You need to measure 1.5 µL. What pipette and tip should you use, and what are the settings? Answer: Use a P2 micropipette with a small yellow tip. Set the dial to 1-5. Problem 5: You want to measure 25 µL of liquid. How would you set the volume on a P20 and a P200? Answer: On a P20 with a small yellow tip, set the dial to 2-5. On a P200 with a small yellow tip, set the dial to 0-2-5. Problem 6: What happens if you use a small yellow tip with a P1000 micropipette? Answer: The small yellow tip is incompatible with the P1000 and will result in inaccurate measurements. Always use a large blue tip for the P1000. Problem 7: Calculate the total volume transferred if you pipette 100 µL with a P200 ten times. Answer: The total volume is 100µL × 10 = 1000µL. 3