A pipette, also known as a pipette gun, is a device used to quantitatively transfer liquids. When conducting research in analytical testing, pipettes are generally used to remove small or trace amounts of liquids. Pipettes can be divided into gas piston pipettes and external piston pipettes according to the principle. Gas piston pipettes are mainly used for standard pipetting, and external piston pipettes are mainly used to handle special liquids such as volatile, corrosive and viscous.
How to choose a pipette
1. Short movement distance of the thumb to complete a pipetting cycle means higher comfort;
Compare the thumb force required for a pipette of the same volume to complete a single discharge (must be pressed to the end). This is the key to affecting comfort. The less force means the less risk of finger damage caused by long-term use;
2. When loading and unloading the suction head, the more labor-saving the better;
3. The weight of the pipette is moderate, too heavy will increase the burden on the hand, but too light also often means that the material may be slightly poor;
4. Other auxiliary designs, such as the frosted design of the shell and the design of finger hooks, help to further improve the comfort.
How to use the pipette
Before pipetting, ensure that the pipette, tip and liquid are at the same temperature.
When aspirating the liquid, keep the pipette upright and insert the pipette tip 2-3 mm below the liquid surface.
Before suctioning, you can pump and release the liquid a few times to wet the nozzle. There are two pipetting methods available at this time.
One is forward pipetting. Press the button with your thumb to the first stop, then slowly release the button to return to the origin. Then press the button to the first stop point to discharge the liquid, stop for a while and continue to press the button to the second stop point to blow out the remaining liquid. Finally release the button.
The second is the reverse pipetting method. This method is generally used to transfer high-viscosity liquids, biologically active liquids, easily foaming liquids or very small liquids. First, suck in more liquid than the set range, and do not blow out the residual liquid when transferring the liquid.
First press the button to the second stop, and slowly release the button to the origin. Then press the button to the first stop point to discharge the liquid with the set range, continue to hold the button at the first stop point, remove the pipette tip with residual liquid, and discard it.
How a pipette works
The basic principle of the pipette's work is that the piston realizes the suction and discharge of liquid through the telescopic movement of the spring.
Pushed by the piston, part of the air is removed, and the liquid is sucked in under the action of atmospheric pressure, and then the air is pushed by the piston to discharge the liquid.
Due to the elasticity of the spring, the speed and force of the pipetting can be well controlled if the pipette is operated with this feature of the spring.
The ordinary micropipette type adopts a built-in gas piston. The piston is designed inside the pipette and relies on pushing air to perform suction and discharge. The piston does not directly contact the liquid.
Another type of pipette uses an external piston. The piston is designed inside the tip and is in direct contact with the liquid. It is suitable for the operation of liquids with relatively high viscosity or easy generation of air bubbles.
Common sense of the use of pipettes
1. Select a medium-range tip.
2. Use appropriate force when installing the suction head.
3. The depth and angle of the tip contacting the liquid surface are the same.
4. For samples at room temperature, the tip is pre-rinsed to improve the sampling accuracy.
5. Maintain a reasonable suction speed.
Recommendations for the use of pipettes
1. Maintain the correct posture when pipetting.
2. Regularly check the sealing condition of the pipette. Once the seal is aging or leaking, the sealing ring must be replaced in time.
3. Correct the pipette 1-2 times a year (depending on the frequency of use).
4. For most pipettes, before use and after using for a period of time, apply a layer of lubricating oil to the piston to maintain tightness.
