Air Displacement Pipette

When using positive displacement pipettes there is no elastic air space to expand or contract so the aspiration force remains constant unaffected by the physical properties of the sample.

Air displacement pipette.

In air displacement pipettes a certain volume of air remains between the piston and the liquid. Positive displacement pipettes are a type of pipette that operates via piston driven displacement. In an air displacement pipette an air cushion separates the liquid in the plastic tip from the piston inside the pipette. No air cushion therefore no problem.

Laboratory pipettes can function either via air displacement or by positive displacement principles. When enabled the pressure is monitored in the tip. As with any gas the air cushion varies according to the characteristics of liquids as well as in part by lab or. Both pipette types have a piston that moves in a cylinder or capillary.

Getting down to the basics an air displacement pipette is a common laboratory tool used to handle a measured volume of liquid between 1 µl to 1000 µl 1 ml. Adjust pipette to liquid becomes fixed volume pipette for adjusted volume. Too low too high volume is pipetted. These pipettes operate by piston driven air displacement.

A vacuum is generated by the vertical travel of a metal or ceramic piston within an airtight sleeve. Acids bases and solvents are the worst enemies of any air displacement pipette. These liquids tend to vaporize in the tip which raises the air pressure resulting in liquid dripping from the tip. The liquid s density influences the size of air cushion e g.

However conditions such as temperature atmospheric pressure as well as the specific gravity and viscosity of the solution may have an effect on the performance of air displacement pipettes. In positive displacement pipetting the piston is in direct contact with the liquid. As the piston moves upward driven by the depression of the plunger a vacuum is created in the space left vacant by the piston. Air displacement pipette used for standard pipetting applications is highly accurate.

Unlike an air displacement pipette which dispenses liquid using an air cushion in the pipette tip the piston in a positive displacement pipette makes direct contact with the sample allowing the aspiration force to remain constant.