gillson or Finn micropipetas are one of the most commonly used instruments in a molecular biology laboratory they're used in conjunction with plastic disposable pipet tips to measure or transfer small amounts of liquids usually from 0.2 microL to 1,000 microL or 1 milll different pipets work across different ranges of volumes and are named by the maximum volume they pipet the different pipets look very similar so they're labeled on the top of each push button with a capital P followed by a number which indicates the maximum volume for that particular pipet a P2 pipets between 0.2 and 2 microL a P20 pipets between 2 and 20 microL a P200 pipets between 20 and 200 microL and a P1000 pipets between 100 and 1,000 microL a pipet is an expensive precision instrument improper use will damage the pipet so correct use is essential you should never use a pipet to measure volumes outside of its range for example using a P200 to pipet too low volume such as 10 microL or too high a volume such as 250 microL will result in inaccurate volume measurements and will damage the internal mechanism of the pipet each pipet has a vertical row of three numbers visible in the body of the instrument to set the volume you can use either the thumb wheel or on newer models the push button this will cause the three number dials in the body of the pipet to rotate and change the volume of liquid that will be taken up however the dial numbers indicate different volumes depending on which pipet is used for example these three pipets have been set to read the same numbers on the dial 152 for the P2 this means that the pipette is set to a volume of 1.52 microL the bottom two dials are in red indicating 5/10 and 2000s of a microL for the P20 this means that the pipet is set to a volume of 15.2 two microL the red bottom dial shows 2/10 of a microL with the P200 the same visual setting means that the pipet is set to a volume of 152 microL this P1000 is set to 052 which indicates a volume of 520 microL a setting of 100 indicates the maximum volume for this pipette which is 1,000 microL the uppermost number is in red which for this pipette indicates the number of milliliters once you've set the volume you need attach the appropriate pipet tip to the end of the pipet p20 and P200 pipets use the same yellow tips p1000 pipets use larger blue tips another type of tip called a filter tip is often used in the laboratory the sterile filter within each tip can help to prevent contamination hold the pipet with one hand with the narrow side resting in the palm of the hand add the pipet tip by gently but firmly pushing the pipet into the pipet tip which is held in a tip box you may need a little practice to learn to apply the right amount of pressure to give a good airtight seal between the tip and the pipet liquid is drawn in and expelled using the pipet's push button gently apply pressure to the button with your thumb until you feel a natural stop this is called the first stop the distance you need to push the push button down will vary depending on the volume you require a P20 set to 2 microL will require less push button movement than a P20 set to 20 microL so to use the pipet push the button down to the first stop then keeping the push button at this level place the pipet tip about 2 mm into the liquid you wish to draw up release the push button by slowly allowing it to return to its original position pause for a second to make sure all the required volume of liquid has been taken up into the tip this is especially important when using more viscous liquids which take longer to draw up withdraw the pipet tip from the liquid and place it inside the recipient container slowly push down on the push button this will release the liquid in the pipet tip into the tube this time push beyond the first stop this ensures that any residual liquid is expelled from the pipet tip fully withdraw the pipet tip from the liquid before you release the push button so to recap push down the push button until you feel some resistance place the pipet into the liquid and slowly release the push button release the liquid from the pipet by pushing past the first stop to fully expel the liquid from the pipet tip into the recipient container withdraw the pipet from the container before you release the button for very small volumes the aspirated liquid can hang in a drop from the end of the tip and may not be transferred to the tube at all so you should touch the tip to the inside wall of the recipient container whilst expelling the liquid once you've aspirated the liquid release the pipet tip from the pipet by pressing down on the tip ejector this is the small white button at the top of the main body of the pipette be sure that the attached pipet tip is inside the appropriate waste container before pressing the tip ejector a new clean pipet tip should be used with each new liquid or if the tip touches any surface or any liquid other than the one you're pipetting if in doubt change the tip do not use a pipette without a tip attached liquid should never enter the body of the pipette it will cause the pipet to corrode and will be a major source of contamination between liquids and experiments do not use a pipet past its volume limits this causes pipetting inaccuracies and also damages the pipet if you're having trouble attaching a tip to your pipet don't repeatedly jam the pipet into a tip this can damage the pipet and if the tip doesn't stay on the end of the pipet simply repeat the procedure with a new tip when pushing down the push button to take up a set volume of liquid don't push past the first stop if you push past the first stop the volume you then take up will be too large when taking up liquids don't simply let go of the push button the liquid can be sprayed around the inside walls of the tip and up into the pipet body causing inaccurate volume dispensing and pipet contamination make sure you release the push button in a controlled manner if you don't pause after you release the push button there won't be enough time for the correct volume to be taken into the tip air will be taken in instead also when you're withdrawing a large volume from a narrow container make sure the tip stays below the surface whenever you have liquid in a pipet tip don't lay the pipet down liquid can get into the body of the pipette which causes crosscontamination pipet damage and inaccurate pipetting and finally remember when pipetting small volumes touch the pipet tip to the side of the tube to ensure the liquid is released into the recipient container