What indicates whether the small amount of fluid in the tip of a pipette that remains after it has drained should be blown out?

What indicates whether the small amount of fluid in the tip of a pipette that remains after it has drained should be blown out?

• A. a frosted band near the top of the pipette
• B. a color band near the top of the pipette
• C. a capital BO near the top of the pipette
• D. absence of TD near the top of the pipette

Answer: (A)

The key idea is how a pipette visually signals whether you should blow out the remaining liquid to deliver the exact calibrated volume. A frosted band near the top is the cue that this is a blow-out pipette, meaning you should expel the last bit of liquid after draining to ensure the delivered volume matches the mark. In practice, you dispense to the receiving vessel and then use the plunger to the second stop to blow out the tip so all liquid is released. Color bands usually indicate something like the pipette’s volume range or brand, not whether to blow out. Markings such as TD (to deliver) relate to blow-out behavior, but the most direct, common indicator you’ll see as soon as you pick up the pipette is that frosted band.

The key idea is how a pipette visually signals whether you should blow out the remaining liquid to deliver the exact calibrated volume. A frosted band near the top is the cue that this is a blow-out pipette, meaning you should expel the last bit of liquid after draining to ensure the delivered volume matches the mark. In practice, you dispense to the receiving vessel and then use the plunger to the second stop to blow out the tip so all liquid is released.

Color bands usually indicate something like the pipette’s volume range or brand, not whether to blow out. Markings such as TD (to deliver) relate to blow-out behavior, but the most direct, common indicator you’ll see as soon as you pick up the pipette is that frosted band.