Most molecular biology experiments include procedures that require extremely small and precise volumes of solutions and reagents. the adjustable micropipette is the tool to measure these quantities accuratel.

• Never use the micropipette or rotate its volume adjuster beyond its maximum or minimum range.
  
• Never use the micropipette without a clean tip in place.
  
• Always hold a filled micropipette vertically, and never lay a filled micropipette down -- the fluid can flow back into the miston mechanism and ruin its ability to measure quantities accurately.
  
• Never allow any part of micropipette to be immersed in any fluid.
  
• Never allow the plunger to snap back after withdrawing or ejecting a sample -- any extreme actions can damage the delicate piston inside.
  

1. First, check that you are using the correct size of micropipette for the volume desired. the micropipettes in our labe can handle three ranges.
   
2. Dial the desired volume -- if you are not sure how, ask for help now!.
   
3. Gently press the end of the micropipette into a sterile pipette tip of the proper size. Be sure that this tip is seated firmly and securely.
   
4. Always replace the cover over the box of pipette tips afterwards to keep them sterile.
   

1. Check that the solutions to be sampled has been thoroughy mixed -- if necessary, vortex or pulse it before proceeding (see below).
   
2. While holding the micropipette away from the solution, depress the micropipette plunger with your thumb down to only the first stop (not the second stop), and keep it pressed down at this position.
   
3. Now, plunge the pipette tip into the solution to be sampled. Remember to hold the micropipette vertically and the tube close to eye level.
   
4. release your thumb steadily from the plunger to slowly draw the fluid into the pipette tip -- check that you are not aspirating any air bubbles.
   
5. Now lift out the micropipette from the tube by gently dragging the filled tip against the inside wall of the tube.
   

1. While still holding the micropipette in an upright position, use your free hand to hold your destination tube at eye level.
   
2. Touch the filled pipette tip lightly against the inside wall of the tube. (The resulting capillary action will later help to draw all of the fluid out of the pipette tip.)
   
3. Steadily depress the plunger beyond the first stop and down to the second stop (to push out every last bit of the sample) but do not let go of the plunger! Keep your thumb pressed on the plunger.
   
4. Now, with your thumb still pressing on the plunger at the second stop, slowly lift the micropipette out while dragging its tip against the inside wall of the tube with a rotational motion of your wrist. All of the fluid within the tip should now be expelled and left withing the receptor tube.
   
5. Dispose of the used pipette tip by pressing the eject button on the micropipette. Always use a fresh pipette tip when changing and dealing with a different solution. (You may reuse a tip for the same solution, provided youhave not contaminated the tip by touching any solution which may have already been in the receptor tube.) Be sure not to contaminate solutions with used tips!
   
6. When combinng reagents together in the single tube, it is a good idea to position each one at a different location midway along the inside wall of the tube. This will help you keep track of which solutions have already been dispensed and will prevent contaminating the pipette tips.
   

1. Close the caps to all of your tubes before placing them into the microfuge.
   
2. Do not attempt to open the microfuge while the rotor is still spinning.
   
3. Always arrange your tubes around opposite sides of the rotor in a balanced configuration. Never spin a single tube by itself; balance it with an empty tube if necessary.
   
4. Position all of your tubes with their hinges pointing outward.
5. Close the lid of the microfuge gently and firmly.
6. Pulse your tubes by manually running the microfuge for 2 - 3 seconds.
   
   

For larger amounts of fluid a variety of glass and plastic disposable and reusable pipettes are available. Common sizes are 1 ml, 5 ml, 10, ml, & 25 ml. These pipettes will frequently have a tuff of cotton located in the neck. These pipettes are usually operated with a dropper bulp or a mechanical pipetter. A dropper bulb may be fitted to the top. The bulb is squeezed, the pipette placed into a liquid, and the requisite amount withdrawn. Graduations on the sides of the pipettes allow you to measure the amount of material withdrawn or pipetted. Our mechanical pipetters consist of a linear apparatus, with a central plunger, and a thumb wheel. The pipette is placed on the top of the pipette with the plunger down. Once in the liquid to be pipetted, the thumb wheel is rotated and the plunger moves up. the resultant vacuum sucks up the liquid. The material is pipetted by reverse operation of the thumb wheel.

Because these units rely upon human observation of the readings and graduations on the side of the pipette, they are not as accurate/repeatable as the micropipetters.

Use a 10 ml pipette to deliver 10 aliquotes of 1 ml each. Use a 1 ml pipette to measure each aliquote. Record the results in you lab notebook. Use a P100 micropipette to measure each aliquote. Record the results in you lab notebook.

Use the P1000 micro pipetter to deliver 10 1 ml aliquotes, use the 1 ml pipette to measure each of these amounts. Record the results in you lab notebook.

• Which instrument was easiest to use?
• Which was the most accurate?
• Which was the most repeatable?
• Which was easiest to use to measure odd amounts?