How to Autoclave Centrifuge Tubes
WHAT IS AUTOCLAVING?
Autoclaves sterilise laboratory equipment by using pressurised high temperature steam to kill all microorganisms within the autoclave chamber. The pressurisation of the steam allows the steam to reach the high temperature that is required for sterilisation.
The CDC (Centres for Disease Control) said that “pressurized steam is the most widely used and dependable method of sterilization”.
HOW DOES AUTOCLAVING WORK?
The autoclave works by removing all of the air in the autoclave chamber, which allows the high pressure and high temperature steam to penetrate all of the surfaces of the object that you are autoclaving.
There are two main ways in how an autoclave removes the air and forces in the steam:
- Gravity autoclaves work by using the basic physics principal of gravity, which is that more dense substances which therefore have more mass will have a greater gravitational pull to the centre of the earth than substances, which are less dense and therefore have less mass. How this works in the autoclaving context is that steam is less dense than air, so when you inject the steam it displaces the air and forces it to leave the chamber through the drain vent at the bottom.
- Prevacuum autoclaves uses a vacuum pump to extract the air from the chamber before the steam is injected. This means that the steam penetrates the object you are autoclaving almost instantaneously (even porous objects).
WHAT CAN YOU AUTOCLAVE?
Although this guide is how to autoclave centrifuge tubes, we’ve included a list of all the laboratory items that are autoclave compatible, and those that are autoclave incompatible. The first most important thing to consider is the melting point of what you are wanting to autoclave, if you are autoclaving laboratory plasticware. For example, you wouldn’t autoclave any low-density polyethylene (LDPE) plastics, as the melting point (according to the University of Texas at Austin) is around 110 °C, which is below the autoclaving temperature of 121 °C. There are also a number of other items that are autoclave incompatible.
AUTOCLAVE COMPATIBLE LABORATORY ITEMS
- Glassware
- Stainless Steel
- Surgical Instruments
- Water
- Biomedical waste
AUTOCLAVE INCOMPATIBLE LABORATORY ITEMS
- Flammable, corrosive, toxic, radioactive or reactive materials
- Any liquid in a sealed container
- Non-stainless Steel
- Acids
- Chlorine based products
WHICH CENTRIFUGE TUBES ARE AUTOCLAVABLE?
You can autoclave centrifuge tubes made from High Density Polyethylene (HDPE) that have a melting point higher than the autoclaving temperature, and those made from stainless steel. Although you can autoclave polycarbonate centrifuge tubes, their life will be significantly reduced. You cannot autoclave any centrifuge tubes made from polyethylene or cellulose propionate.
HOW TO AUTOCLAVE CENTRIFUGE TUBES
Sterilab centrifuge tubes that are autoclave compatible should be autoclaved for 20 minutes at 121 °C. For more help on how to use an autoclave, read this helpful guide created by the University of Washington.
OTHER HELPFUL AUTOCLAVING TIPS
- To avoid deformation of your centrifuge tubes, then autoclave the centrifuge tubes or bottles upside in a tube rack. Autoclave for no longer than 20 minutes at 15 psi, and only remove from the rack once the centrifuge tubes have been able to cool.
- Make sure that you do not autoclave capped or sealed tubes or bottles.
- Never leave any items in the autoclave overnight!
- Always remember to check that the plasticware you are autoclaving is autoclave compatible – not all plasticware is.
- Always wear PPE when operating an autoclave. You’ll need a lab coat, heat resistant gloves and safety glasses.