Filtration of the precipitate from supernatant solution used to be a common laboratory practice in earlier days. The operation was simple to carry out as it involved only pouring the solution gently over a tilted glass rod held against folded filter paper fixed inside a glass funnel .However, the process was time-consuming and took your precious laboratory time.
Today a centrifuge has become a widely accepted laboratory commodity just like a hot plate, pH meter or a thermometer. It affords rapid separation of the precipitate from the supernatant liquid and its separation power is based on the principle of centrifugal force. The solution is spun in circular motion at high speeds and the centrifugal force leads to a collection of suspended particles at the bottom of the centrifuge tube. After a fixed time the centrifuge is stopped and the supernatant liquid is separated. The biggest advantage is rapid separation of the precipitate in more than one tube.
The centrifuge offers substantial time saving but carelessness in use can result in damage to the system as well as injuries to you and others present in the lab.
First of all the potential hazards arising from use of centrifuge are summarized below:
- Breakage of tubes at higher operating speeds
- Spillage of contents of tubes which can damage the tube bowls and other interior parts
- Escape of aerosols of toxic or corrosive liquids into the laboratory environment
- Risk of flying debris of broken tubes
- Risk of contamination by leakage of biologically active or radioactive materials
Minimization of Operational Risks
As in any other laboratory operation safety should be your prime concern. Wear your lab coat and in addition wear safety glasses to protect your eyes. Use of a face shield is recommended if you are centrifuging corrosive, bio-hazardous or radioactive materials. Face shield will additionally provide protection against flying objects.
A lot of problems can be avoided if a few minutes are spent on initial inspection of the system before use :
- Ensure that the centrifuge bowls and tubes are free of any spillages or broken tube debris.
- Inspect the centrifuge tubes. These should be free of any cracks and are provided with sealing caps to prevent leakages during centrifugation
- The rotor is properly seated and is fitting security to the central drive hub
Care During Operation
- Use preferably unbreakable plastic centrifuge tubes
- Avoid overfilling the tubes as it can result in spillages during runs. Centrifugal force can push the solution upwards along the tube walls during high-speed runs
- Ensure that filled tubes are properly seated in the buckets before the start of run
- The opposite tube pairs should be properly balanced in terms of weight before the start of centrifugation
- Operate only within manufacturer prescribed run speeds
- Properly close tubes before running .Covering with an aluminium foil is of little help as it can fly off or rupture during the process.
- Always close the top cover before operating the system
- Allow the centrifuge to come to rest before opening the top cover. In case hazardous materials are being handled allow at least 10 – 15 minutes before opening the cover
- Do not attempt to move the centrifuge position when it is operating
- Keep a spill kit ready in proximity to handle spills in case of emergencies
- Use bio-safety cabinet for opening centrifuge tubes containing bio- hazardous samples
Post Operation Care
Post operation inspection before leaving the centrifuge is of equal importance as pre operation inspection.
- Make required entries in the user log book on using the centrifuge
- Open the centrifuge carefully after waiting and make sure it is free of any spills
- In case of minor spills inside clean with a mild detergent using a soft brush and rinse with de-ionized water and finally dry with clean tissue
- Inspect for any damage to the rotor or wells and report it to laboratory in- charge for timely rectification or replacement
In summary it can be said that a centrifuge is a useful laboratory appliance but requires adherence to essential safety guidelines during use.