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A graduated pipette is a pipette with its volume, in increments, marked along the tube. It is used to accurately measure and transfer a volume of liquid from one container to another. [ 1 ] It is made from plastic or glass tubes and has a tapered tip.
A volumetric pipette, bulb pipette, or belly pipette [1] allows extremely accurate measurement (to four significant figures) of the volume of a solution. [2] It is calibrated to deliver accurately a fixed volume of liquid.
Pipettes come in several designs for various purposes with differing levels of accuracy and precision, from single piece glass pipettes to more complex adjustable or electronic pipettes. Many pipette types work by creating a partial vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid.
When the pipette knob is pressed on an air displacement pipette, the piston inside the instrument moves down to let air out. Air is displaced by the piston. The volume of air displaced is equivalent to the volume of liquid aspirated. These pipettes are capable of being very precise and accurate.
Since the piston makes direct contact with the sample, the aspiration force in a positive displacement pipette is unaffected by the sample's physical properties. [3] Several liquid handling companies suggest that positive displacement pipettes can be used to accurately pipette very viscous, volatile, hot or cold, or corrosive samples. [4] [5 ...
These pipettes commonly have a label with their volume range like "10–100 μL". These limits are indeed the limits as overwinding these limits would result in damage of the pipetting system. The fixed volume pipette cannot be changed. As there are less moving parts, the mechanism is less complex, resulting in more accurate volume measurement.
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