How to Use Refrigerated Centrifuges

Principle of procedure

• A centrifuge separates particles in a liquid by sedimentation. Dense particles sediment first, followed by lighter particles
• To obtain a high sedimentation efficiency of 95%, it is necessary to centrifuge the TB specimens at 3,000 g for 15-20 minutes
• The high speed and time used to achieve effective sedimentation efficiency lead to heat build-up in the centrifuge and the specimens.  To prevent cell death due to overheating, the use of a refrigerated centrifuge is recommended

How to use refrigerated centrifuges?

Select type of tube, based on:

• G force used for swing-out bucket
• Time of centrifugation 
• Temperature
• Compatibility with specimen 
• Chemically inert

Visually inspect tubes  

Do not use if tubes have:

• Cracks
• Scratches
• Chipped rims

Fill tubes only to the recommended volume

• Do not overfill tubes
• High g forces can drive liquid up to the cap and cause overflowing

Before using centrifuge

• Inspect the interior of the bowl for stains
• Inspect rotors and buckets for cracks and signs of corrosion
• Always check the silicon O ring for any wear & tear of the aerosol lid
• Check log book to ensure centrifuge is in good working condition
• Pre-cool centrifuge prior to use

Use of safety centrifuge

• Centrifuge load MUST always be balanced to avoid the risk of damage
• Add a balance tube with the same volume of water if processing an odd number of specimens
• Select the required time and g force or RCF 
• Stop centrifuge immediately if any abnormal noise and/or shaking is noticed
• Never use the brake to stop a normal operating centrifuge for TB specimen processing
• ALWAYS open the sealed buckets inside the biosafety cabinet (BSC)

Microcentrifuge

• Always balance the rotor 
• Use high-quality screw-capped tubes, which will not leak or break during centrifugation 
• When using a microcentrifuge for DNA extraction, the microcentrifuge should be loaded and unloaded inside the BSC
• Remove and replace the rotor carefully

Resources

• World Health Organization laboratory biosafety manual 3rd edition, pgs 72-73 
• Manufacturer's instructions
• Global Laboratory Initiative LC training module on Equipment slides 32-34.

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