Micropipette Quiz
Questions: 16 · 10 minutes
1. Which sequence describes reverse pipetting for a liquid suited to that technique?
Press to the first stop, aspirate, then dispense repeatedly without releasing the plunger
Aspirate with the plunger fully released, then dispense only to the second stop
Press to the second stop, aspirate, then dispense to the first stop and leave the residual liquid in the tip
Press to the second stop, aspirate, then dispense through the second stop so no residue remains
2. Which statement best distinguishes calibration from adjustment of a micropipette?
Calibration replaces the piston, while adjustment replaces the tip cone
Calibration cleans the pipette, while adjustment sterilizes it
Calibration applies only to fixed-volume pipettes, while adjustment applies only to variable-volume pipettes
Calibration evaluates performance against a reference; adjustment changes the instrument to bring performance within requirements
3. Before making a series of precise transfers, a technician aspirates and dispenses the same liquid two or three times using the attached tip. What is the main purpose of this pre-wetting step?
To sterilize the inside of the tip with the sample
To confirm that the pipette's calibration certificate is current
To increase the pipette's maximum operating volume
To condition the tip and reduce volume variation caused by evaporation or surface effects
4. In standard forward pipetting, what is the purpose of pressing from the first stop to the second stop at the end of dispensing?
To blow out liquid remaining in the tip
To aspirate an extra volume for the next transfer
To reset the pipette's calibration electronically
To release the disposable tip from the tip cone
5. In a gravimetric performance check, how is the volume of dispensed water typically determined?
By reading the liquid level directly from the disposable tip markings
By measuring the water's mass and converting it to volume using appropriate density-related factors
By timing how long the pipette takes to dispense
By comparing the plunger force with that of a larger pipette
6. A pipette continues to leak after a fresh compatible tip has been seated correctly and the technique has been checked. What is the most appropriate next step?
Remove it from critical use and have its seal, piston, or tip cone inspected according to service guidance
Compensate by setting a slightly larger volume for every transfer
Apply laboratory grease to the outside of each disposable tip
Operate it above its stated maximum volume to reseat the piston
7. During aspiration, the tip is submerged much deeper than necessary. What is the most likely technique-related concern?
The tip's nominal capacity permanently increases
The pipette automatically changes from air displacement to positive displacement
Extra hydrostatic pressure and liquid coating the tip exterior can contribute to transfer error
Deep immersion prevents any liquid from entering the shaft
8. Which practice is generally appropriate when storing a micropipette after use?
Leave a used tip attached to protect the tip cone from air
Remove the tip and place the pipette upright on a suitable stand, following the manufacturer's instructions
Lay the pipette horizontally with liquid remaining in the tip
Store it resting on the plunger so the piston remains compressed
9. A sample repeatedly enters the tip too quickly and occasionally splashes or forms bubbles. What should the operator change first?
Allow the plunger to rise smoothly and consistently during aspiration
Release the plunger abruptly so the liquid reaches the piston faster
Use the tip-ejector button to regulate aspiration speed
Rotate the volume control while liquid is entering the tip
10. A researcher must transfer a clean buffer after pipetting a sample that could contaminate it. What is the most appropriate routine action?
Reuse the same tip if no droplet is visible on its exterior
Eject the used tip and attach a new compatible tip before transferring the buffer
Rinse the used tip once in the clean buffer and continue
Increase the volume setting to flush contamination into the buffer
11. After attaching a disposable tip, a pipette drips despite careful plunger control. Which issue should be checked first?
Whether the volume display uses three or four digits
Whether the liquid was dispensed against the wall of the receiving vessel
Whether the tip is compatible, undamaged, and seated evenly enough to form a seal
Whether the pipette was held horizontally during tip ejection
12. You need to transfer a volume that falls within the stated ranges of several micropipettes. Which choice will generally support the best accuracy?
A pipette set near the bottom of its range, regardless of other suitable choices
The largest-capacity pipette available, because its piston travels farther
Any pipette that can display the target number, even if the volume is below its stated range
The smallest-capacity pipette whose stated operating range includes the target volume
13. A multichannel pipette repeatedly leaves one row of wells with lower volumes than the others. What should be investigated first?
Uneven tip seating, incompatible tips, or a sealing problem on the affected channel
Whether the microplate contains an even number of wells
Whether the volume display is facing the operator during dispensing
Whether the plunger was held at the second stop before the tips were attached
14. A pipette set to 100 µL produces repeated results of 98 µL, 102 µL, 99 µL, and 101 µL under controlled conditions. How are these results best described?
Highly precise but systematically inaccurate, because every result is identical
Neither accurate nor variable, because all values must equal exactly 100 µL
Accurate on average, with some spread indicating limited precision
Perfectly accurate and perfectly precise, because the average is near 100 µL
15. A user holds an air-displacement micropipette at a steep angle while aspirating. Which change is generally most appropriate?
Keep the angle but press directly to the second stop before aspiration
Keep the angle and immerse the entire disposable tip
Turn the pipette horizontal so the liquid spreads along the tip
Hold the pipette close to vertical during aspiration
16. When aspirating liquid with a standard air-displacement micropipette, where should the plunger normally be before the tip enters the liquid?
Fully released, followed by pressing while the tip is submerged
Pressed smoothly to the first stop
Pressed to the second stop and held there throughout aspiration
Repeatedly moved between both stops to remove air from the tip