The centrifuge is a biotechnology laboratory tool that has been used for hundreds of years. The first centrifuges were powered by a hand crank which was used to spin the holding compartment or compartments quickly around an axis in the center of the machine. Spinning these materials at high speeds applies a pressure to the materials in the centrifuge equal to many times the force of gravity. With this amount of pressure placed on the materials, the less dense materials quickly “float” to the center of the centrifuge while the denser materials “sink” to the outside of the machine. Currently, digital centrifuges are used for many applications and are commonly found in biotechnology laboratories to separate sample components and during purification techniques.
The purpose of this lesson is to explore the concepts behind centrifugal force, perform centrifugation with assistance and determine the accuracy of data collected during an investigation requiring the use of a centrifuge. The following video as well as instructor notes and student notes can be helpful when preparing for the proper use of a laboratory centrifuge.
1. Gather the liquids and mixtures being investigated.
2. Add an equal volume of each liquid to each centrifuge tube and record the location of each sample using the numbers found on the rotor of the centrifuge.
3. Place the centrifuge tubes in either a table top or microcentrifuge being certain arrange the tubes so that the equipment is balanced.
4. Centrifuge the tubes for 2-5 minutes on high speed. Allow the centrifuge to come to rest and gently remove the tubes without disturbing the contents.
5. Record the results on a data table or chart such as the example provided.
6. Repeat using the same liquid samples and centrifuging for 1-2 minutes on low speed.
Centrifuges are one of the most misunderstood and misused tools in the biotechnology lab. Here are a few tips to ensure the successful and proper use of this potentially dangerous laboratory tool:
1. There may be more than one model of centrifuge in your lab. Be certain to become familiar with each model and the subtle yet important differences in each.
2. Make sure to close the caps on all the tubes to be placed in the microcentrifuge. There are some exceptions to this rule however for the most part you will need to seal the containers.
3. The microcentrifuge rotor must always be balanced - for example, you cannot insert only one tube into a microcentrifuge. Spinning in an unbalanced arrangement of tubes can damage the motor of the instrument and potentially cause serious harm to the operator of the centrifuge.
4. After the lid and/or metal top (some centrifuges only) is secured, give the tubes a 1-2 second pulse to be certain the centrifuge is properly balanced. You will be able to hear and possibly hear a loud shaking noise if the rotor is unbalanced. This will also mix and pool all the reagents to the bottom of each tube.
5. Do not EVER open the lid until the centrifuge comes to a complete stop and "BEEPS" or other indicator such as the turning off of a light on the centrifuge.
To conclude this skill building lesson, students have an opportunity to repeat and rehearse the centrifuge technique executed in the hands-on lab they have completed in a virtual lab setting. The NC BioNetwork virtual centrifuge lab affords students a unique way to experience the principles of centrifugation and gained an official certification in proper biotechnology lab tool.