Hobbies And Interests
Pipette Function
Most of the pipettes used in laboratories are the air-displacement pipettes, which operate through measuring and transferring solution. The mechanism used is a piston that is activated by the users' thumb. A vacuum is created in the open space. The tip on the pipette is placed in the solution and filled with the indicated volume of solution.
Calibration
Calibration is necessary before adjusting or using a pipette. Pipettes are usually calibrated using gravimetric analysis. Gravimetric analysis dispenses samples of distilled water into a receiving vessel in a precision analytical balance. The density of water, temperature, pressure and humidity are noted. The mass of the dispensed sample of water results in the accurate indication of the volume dispensed.
Air Displacement Pipette Adjustment
In order to adjust an air displacement pipette, the piston on the pipette needs to be placed in the appropriate position. The piston will move to the appropriate position when the volume needed is set. As the operating button is pressed, the piston expels the same volume of air as the set volume. The pipette tip is placed in the solution and the operating button is released allowing the solution to enter the pipette tip. In order to pipette different volumes, the volume indicator is adjusted.
Positive-Displacement Pipette
A positive-displacement pipette use disposable pipette tips in order to avoid sample contamination. The pipette is adjusted to the volume needed. As in the air displacement pipette, the piston moves to the right position as the volume is sets. The operating button is pressed to the stop and the piston moves to the tip opening. The tip is then immersed in the solution and the operating button is released. The solution enters the tip. The operating button is pressed again to release the solution. In order to re-adjust the amount of solution needed, the volume needs to be re-set and a new pipette tip needs to be placed on the tip of the pipette.