Intro: How to Pipette
Using a pipette is an essential part of working in a science laboratory. Pipettes, specifically micro-pipettes, are used for accurately measuring and transferring small amounts of solutions from on container to another. This is useful when creating a dilution series, plating cell samples. etc.
Although each pipette brand varies slightly, micro-pipettes generally come in three sizes; the P20 which can pipette from 2-20 uL, the P200 which can pipette volumes from 20-200, and the P1000, which - you guessed it - can pipette volumes ranging from 200-1000 uL or 1 mL.
Continue reading for step-by-step instructions on how to use a pipette.
Step 1: Materials
To pipette, you will need:
-A box of tips
-A container holding the solution you wish to pipette
-An empty container for the solution(s) to be transferred into
-A clean working space
-A waste bin
-Gloves if you don't like your hands getting dirty or you are working with potentially hazardous materials
Step 2: Setting the Volume
The first step when using a pipette is setting the pipette to your desired volume. To do this, locate the small window on your pipette that has three numbers in it. If your pipette has a lock/unlock switch, switch it to the unlock position. Then, turning the plunger clockwise or counter-clockwise until you reach the desired amount. For the picture above, the pipette being used is a P200 and it is set a 175 uL. It is very important to stay with in the volume limits of your pipette, which depend on it's size, because even though you may be able to get smaller or bigger amounts, the pipette is not designed to be used with those amounts and it could end up breaking your pipette.
Step 3: The First and Second Stops
Nearly all pipettes have two 'stops' on the plunger. Before you start using the pipette, it is a good idea to play with the plunger a bit to feel these two different stops. The first stop is the stop that changes; it is the amount that you set the pipette to in the previous step, and it is shown by the first picture. The second stop, shown in the second picture, is an extra 'push' that it sometimes needed to remove all of the liquid from the tip. When to use these two stops with be discussed in later steps.
Step 4: The Pipette Tip
First of all, make sure you have the correct pipette tip size and brand to match your pipette! If the tip doesn't fit on the end of your pipette, it is not the right size. To put a tip on your pipette, open the tip box and place the end of the pipette into one tip. Press down gently, but firmly, to ensure that the tip is firmly on the pipette. You may then take the pipette away from the box and the tip should come with it. Close the pipette tip box to help prevent contamination.
Step 5: Depressing the Plunger
Now that you have a tip on your pipette, you are ready to start pipetting! Press the plunger down until the first stop - be careful to not go past the first stop! Depress the plunger BEFORE you put your pipette into the solution - otherwise bubbles can be created, introducing air that can cause contamination and other problems.
Step 6: Withdrawal of Solution
After depressing the plunger, carefully place the tip of your pipette into the desired solution. Try not to touch the sides of the container as you do this. Once the tip is in the solution, slowly release the plunger and the set amount of solution will be pulled up into the tip, then remove the tip from the solution and close the container. If there are any air bubbles in the tip, start again as this could affect the amount of solution.
Step 7: Expulsion of Solution
Place the tip into the new container, again being careful to not touch the sides of the container to prevent contamination, and as far into the container you can go without touching the sides. Slowly push the plunger down all the way to the first stop, then the second stop to make sure all solution has been pushed out of the tip. Once done, remove the pipette from the container and close the lid.
Step 8: Discarding the Tip
Now that you've successfully measured and transferred your solution, it is time to get rid of the tip. To do this, press down on the tip ejector button, which is a small button usually next to the plunger, while holding the pipette over a waste bucket. This will move a metal or plastic arm down, forcing the tip off of the pipette. It is always a good idea to change tips when you are changing solutions, or if it touches any surface; these both reduce risks of contamination.
Congratulations, you made it! You have successfully learned how to pipette. Now that you know this essential science skill, a world of pipetting possibility awaits!