How to Use Pipettes
Pipettes allow you to transfer liquid, often in small volumes, from one vessel to another. To use a pipette, you first need to aspirate a liquid into its tube. The process is similar to sucking liquid into a drinking straw, but instead of using your mouth, you use a bulb or pump. Learn more about how to use pipettes below.
What Is a Serological Pipette?
Pipettes come in several forms. A serological pipette allows you to measure liquids in milliliters (mL) and has markings along the side to help you accurately gauge the amount of liquid. Sizes vary — some pipettes hold just 1mL, while others hold up to 50mL. These pipettes can be made from glass or a clear plastic, such as polystyrene.
Using a Pipette
To use a pipette, you'll need the pipette and a bulb or pipette filler to aspirate the liquid. Some pipettes have a bulb attached at the end, while others require a separate bulb that fits over the upper opening.
Choose the correct size pipette based on the volume of liquid you're transferring. It needs to be slightly larger than the total volume — for example, use a 50mL pipette if you plan on moving 45mL of liquid.
Attach the bulb or pipette filler to the pipette if it isn't attached already, squeeze the bulb to release air from the pipette and then place the opposite end into the liquid. If using a safety bulb, aspirate and dispense according to the manufacturer's instructions. Release the bulb, depress the aspirate button or rotate the aspiration wheel on the pipette filler to draw the liquid into the pipette's tube. Stop releasing the bulb or aspirating the pipette filler once you have an adequate amount of liquid.
If the bulb has a side valve, place your finger firmly across it to create a vacuum and keep the liquid from spilling out while moving the pipette. Otherwise, carefully remove the pipette from the liquid without squeezing the bulb. Next, move the pipette to the container where you want to dispense the liquid. Remove your finger from the valve (or carefully remove the bulb if it does not have a valve while maintaining the same pressure on the bulb), and the liquid should flow out.
Serological pipettes typically need to be blown out to remove the last drop of liquid. This liquid should be discarded. To do this, place the bulb back over the upper opening and squeeze it above a waste container. The remaining drops should flow out into the container.
How to Read a Pipette
Serological pipettes have markings along their length, which usually read from largest near the tip to smallest near the upper opening. The top of the liquid will form a meniscus, or concave shape, inside the pipette. When measuring the volume, read from the bottom of the meniscus, not across the top.