The centrifuge – process and safety

And with that the students proceed to observe Dr Smith as she demonstrates the correct use of the centrifuge:  

She points out that the procedure itself is straightforward and lists the steps for the students: 

1. Prepare your tubes with the correct volume of fluid, making sure each pair is balanced in weight. If you have an odd number of samples, create a dummy tube with water or buffer to match the heaviest sample.

2. Place the tubes in opposite slots on the rotor. Secure the lid.

3. Set your speed and time according to the protocol. The revolutions per minute (RPM) or ‘g-force’ values should be chosen based on what you’re trying to separate.

4. Start the run and stand close for a moment to listen for unusual noises. If you notice rattling or wobbling, stop the run immediately, rebalance, and try again. This is a common error so extra care should be taken.

5. After the timer runs out, wait for the rotor to halt fully before opening the lid. Pull out your tubes gently—there may be a pellet at the bottom you don’t want to resuspend accidentally.

While the centrifuge is running, you and some of the other students are studying. Emma tries to open the lid while the rotor is still spinning. Dr Smith turns around and sees her. 

Dr Smith: ‘Emma, I noticed you tried to open the lid while the rotor was still spinning. We need to keep that lid locked until the machine has come to a complete stop—spinning rotors can be hazardous.’ 

Emma: ‘Sorry Doctor I was just so excited to see what happened to our sample!’

Dr Smith nodded and continued. ‘Since we are discussing safety, you also need to verify that the centrifuge is balanced each time you place tubes so we don’t get excessive vibration that might damage both the equipment and your samples. Does anyone know what balance means in this case?’

You: ‘Yes. We need to make sure that there is a tube opposite each tube in the centrifuge.’ 

Dr Smith: ‘Great job everyone! Let’s move on to final section of our basic laboratory equipment.’

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