2023-11-11 05:33:52
Introduction
Gilson pipette fitted with its tip
An automatic pipette or micropipette or automatic pipettor is a precision pipetting system used, among other things, in analytical chemistry and in molecular biology (Molecular biology (sometimes abbreviated bio mol or BM) is a discipline…). Brands include Pipetman® (registered trademark of Gilson®) and Finnpipet®.
Description
These are systems operating pistons. The modification of the length of the air column (Air is the mixture of gases constituting the Earth’s atmosphere. It is odorless and…) inside the device allows volumes of liquids to be sucked up or expelled with great precision.
A wheel allows the user to adjust the volume to be sampled, using a digit indicator.
There is generally a range of models depending on the volume to be pipetted and the precision of the sampling to be carried out:
P5000: allows pipetting up to 5 ml of solution; P1000: allows pipetting from 200 to 1000 µl of solution; P200: allows pipetting from 20 to 200 µl; P20: allows pipetting from 10 to 20 µl; P10: allows pipetting from 0.5 to 10 µl.
Pointes
It is necessary to have tips (or “tips” or “cones”) that are adapted to the micropipette used. These tips must be as tapered as possible, especially for small volumes, in order to better see the volume taken. They are generally placed in sterilizable boxes, provided with a perforated tray, where they are placed.
There are tips equipped with a cotton filter. They help avoid contamination that could come from the plastic of the pipette or the air column.
There are also boxes in sterile packages already filled with tips. These boxes are disposable.
A tip is collected simply by applying the tip of the micropipette into the neck of the tip. By pressing a little, the tip sinks in and can be removed from the box.
A tip ejector allows you to dispose of the soiled micropipette tip without using your hands.
Setting
A small wrench allows you to tighten or loosen a screw modifying the length of the air column and allows you to adjust the micropipette.
Automatic pipettes must be calibrated regularly to keep the volume they draw accurate.
Utilisation
We start by setting the volume to be sampled without exceeding the range of the pipette: that is to say the range of volumes for which it is designed.
For example, a “P20” (10 µl to 20 µl) should not be set less than 10 µl or more than 20 µl. It is also between these two values ​​that the precision is best.
To pipette, we hold the automatic pipette (An automatic pipette or micropipette or automatic pipettor is a pipetting system…) by the body with the four fingers of the hand (The hand is the prehensile effector organ located… ) right (if you are right-handed) and the thumb is used to operate the piston or the cone ejector.
Automatic pipettes have two notches depending on the force applied to the piston:
the first allows the liquid to be sucked in (The liquid phase is a state of matter. In this form, the matter is…) with the right pressure (Pressure is a fundamental physical concept. We can see it as a force reported…) corresponding to the chosen volume; the second allows the ejection of the collected liquid so that nothing remains in the cone. Indeed, a viscous liquid (loaded for example with proteins or nucleic acids) tends to adhere to the walls.
Care must be taken not to take with the second notch (i.e. go beyond the first notch and reach the second), because in this case too large a volume is sucked up, moreover the liquid is likely to enter the mechanics of the pipette and damage it.
When trying to take precise samples, it is important to immerse the cone as little as possible to prevent liquid from adhering to the outside of the cone.
The left hand is used to hold, open or close the microtubes.
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