To dispense a volume of 100 µL as accurately as possible, which of the three autopipettes provided in the teaching labs would you use, and why?

Question

BlackTom AI · Accepted Answer

Pipettes give their best accuracy and precision when used near the top (close to their maximum) of their calibrated volume range, and repeated aliquot transfers increase cumulative error. These two concepts determine the best choice.

Step‑by‑step reasoning:
1) Compare available pipettes and the target: 100 µL. The 10–100 µL pipette can be set to 100 µL and deliver the whole volume in one stroke. The 0.5–10 µL and 10–100 µL could in principle deliver 10 µL aliquots ten times to reach 100 µL; the 100–1000 µL pipette can deliver 100 µL but at its minimum setting.  
2) Accuracy vs range position: Manufacturers specify best accuracy near 100% of a pipette’s range. Using a pipette at the top of its range (e.g., 10–100 µL at 100 µL) gives smaller systematic and random error than using the same pipette near its bottom. Similarly, using the 100–1000 µL pipette at 100 µL (its minimum) places it at the worst part of its range.  
3) Error accumulation: If you dispense multiple aliquots, any random error in each dispense accumulates. For independent random errors with standard deviation s per aliquot, the combined standard deviation after n aliquots is sqrt(n)·s, so doing 10 × 10 µL transfers produces greater overall uncertainty than one 100 µL transfer from an appropriately sized pipette.

Why C is correct:
- The 10–100 µL pipette set to 100 µL uses the instrument at its optimal point and requires only one dispense, minimizing both single‑dispense error and cumulative error from repeats.

Why the other options are incorrect:
- A: 0.5–10 µL used ten times increases cumulative error and is unnecessary.
- B: 10–100 µL set to 10 µL is at the low end of its range and repeated transfers compound error.
- D: 100–1000 µL at 100 µL is at the bottom of that pipette’s range and less accurate.

Final confirmation: therefore option C is the correct choice.

To dispense a volume of 100 µL as accurately as possible, which of the three autopipettes provided in the teaching labs would you use, and why?单项选择题

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