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Biology LibreTexts

2.6: Exercise 2 - How NOT to pipette!

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    1. Use the P1000 to add 990 μL of water to two microcentrifuge tubes. Label the tubes A and B. Dispose of used tips in the containers provided on the benchtop.

    2. Use a P20 to correctly transfer 10 μL of 0.05% BPB to tube A. Make a mental note of what fraction of the pipet tip is filled with the dye. Use the vortex mixer to disperse the BPB in the water.

    3. Use a P20 to INCORRECTLY transfer 10 μL of 0.05% BPB to tube B. Do this by depressing the plunger to the second stop before you take up the BPB solution. Make a mental note of how well the dye fills the tip this time.

    4. Set the wavelength of the spectrophotometer to 590 (A590). Pipette 1 mL of water into a plastic cuvette and blank the spectrophotometer at this wavelength.

    5. Read the A590 of the solutions in tubes A and B, in the spectrophotometer. How do the two readings compare? What kind of error results from drawing solution into the pipette incorrectly?