Question

1. For optimal accuracy, do you recommend choosing a larger or smaller sized flask? On what do you base this decision?

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Table 2: KIMAX Brand Reusable Volumetric Pipets, Class A % Relative Tolerance Capacity (ml) 0.5 1 0.6 0.5 0.3 Tolerance (ml) 0.006 0.006 0.01 0.01 0.01 0.02 0.03 0.03 0.03 0.05 0.08 0.4 0.3 0.2 0.2

2. Jamie needs to pipet 1 mL of bovine serum albumin solution into a test tube. Two options are available: a 1 mL pipet and a 1000 µL micropipet. Refer to Table 2 for information about the volumetric pipet tolerances. Data for the micropipet appear below. Which pipet will deliver the more accurate volume? Explain your reasoning.

Answer 1

(a) Accuracy is the measure of how close the measured value is to the true value. Tolerance is the allowed range of variation from the actual value.

To choose between a larger and smaller sized flask for optimal accuracy, it is smaller sized flask. It is because it is very clear from the table that small sized flasks having lesser capacity showed more tolerance than large sized flasks having greater capacity and more tolerance means more accuracy. Hence, small sized flasks are prefered.

(b) Since we prefer small sized flasks for optimum accuracy, it is advisable to use a 1000 $\mu$ L pipet. From the two tables, it is clear that if you use a 1000 $\mu$ L pipet instead of a 1 mL pipet for a small sized flasks, it shows more tolerance and accuracy and hence, will deliver more volume.

For example, for a small sized flask of 0.5 mL capacity, if you use a 1 mL pipet, the accuracy is about 6%. But if you use a 1000 $\mu$ L pipet, the accuracy is 8%.