Which pipette type should be used when a strict, specific volume is needed?

A volumetric pipette is specifically designed to measure and deliver a single, precise volume of liquid. It features a bulb in the middle and a narrow stem, allowing for accurate measurement when filled to a specific mark. This level of precision is critical in many laboratory applications where exact volumes are necessary for reactions or experiments, thus making the volumetric pipette the ideal choice for tasks requiring strict volume specifications.

In contrast, other types of pipettes serve different functions. A graduated pipette allows users to measure and dispense a range of volumes, but it may not provide the same level of accuracy as a volumetric pipette for a specified volume. A Pasteur pipette is primarily used for transferring small amounts of liquid rather than precise measurements. Similarly, a disposable plastic transfer pipette is also meant for transferring liquids, often in informal or educational settings, and lacks the precision required for strict volume requirements. Therefore, when exactness is paramount, the volumetric pipette stands out as the best option.