Micropipettes are a common type of laboratory equipment designed to transfer and measure very small amounts of liquid. They can be used to measure volumes as low as 0.003 ounce (0.1 milliliter). Standard micropipettes used in laboratory settings feature a few basic parts including an adjustment dial and a plunger button. Plungers on micropipettes are depressed with the thumb and when released, liquid can be drawn into a special plastic tip. There are several different sizes, types and styles of micropipette available.
The average micropipette consists of several components including a volume adjustment dial and a digital volume indicator. At the end of a shaft, these pipettes also feature an attachment point engineered to accommodate different types of disposable tips. Liquids are drawn into the disposable plastic tips fitted at the end of micropipette shafts instead of into the shafts themselves. The two main buttons found on most micropipettes are the plunger button and the tip ejector button. Pushing the ejector button will cause the pipette to immediately release the disposable tip at the end of the device.
Most micropipette plungers are designed to stop at two different positions. Depressing the plunger to the first stopping position and slowly releasing it will cause the pipette to draw the desired volume of liquid up into its disposable tip. Pressing a micropipette's plunger down further to the second stopping point releases the volume of fluid drawn into the device at the first stop. To draw an accurate measurement, pipette plungers should be pressed down to the first stop point before the pipette tip gets inserted into a sample.
Three of the more common micropipette sizes include P20, P200, and P1000. Each different size is designed to measure liquids within different volume ranges. The P20 micropipette can measure volumes within the range of 0.02 and 0.7 ounce (0.5 and 20 milliliters) while the P200 can measure volumes between 0.7 and 6.8 ounces (20 and 200 milliliters). P1000 micropipettes are some of the larger micropipettes available and are typically employed to measure liquids with a volume in the range of between 3.4 and 33.8 ounces (100 and 1,000 milliliters).
A micropipette's volume adjustment dial helps ensure accurate measurement. This component is used to adjust the volume of liquid entering the pipette's tip. As this dial is adjusted, the digital readout on the volume indicator will change to reflect the adjustment.