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Sterilization |
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Energy-saving sterilization of liquids
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DURAN® Square laboratory bottles
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In the laboratory there is often a requirement for very pure water, saline solutions and various buffers in sterile form. Sterilizing these liquids in an autoclave consumes a great deal of energy, so it is important to utilize the autoclave to its maximum capacity.
DURAN® square laboratory bottles guarantee that autoclaves are used safely and with minimum energy consumption.
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Autoclaving is a very safe and efficient way of sterilizing liquids if all the rules are observed and the correct programs are adhered to. In addition to the observance of these rules, the selection of the right containers is of great importance for safety and sterility.
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What does sterile mean?
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Sterilization means the elimination (removal, destruction) of all microorganisms and the inactivation of all viruses in or on a product or object.
For liquids, two different sterilization procedures are used. Sterile filtration of heat-sensitive liquids is carried out by passing them through a 0.2 µm membrane filter.
As the filtered liquid does not go directly into its final container in such cases, there is always the danger of cross-contamination.
For non-heat-sensitive liquids steam sterilization is still the safer procedure.
“Sterile” must be understood as an absolute term meaning “free from germs capable of reproduction (microorganisms)”.
When testing for sterility it is generally very difficult to prove this condition, since the individual reference methods are selective as a result of different nutrients, incubation temperatures and times.
Quite a few microorganisms are often missed by these test methods because of different properties.
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Glass - the ideal laboratory partner
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Many years of experience have shown that the many possible uses for glass make it an ideal partner in laboratories.
Where liquids are sterilized centrally and then distributed to different laboratory units it has been shown that DURAN® square laboratory bottles are ideal for this purpose.
Because of its high chemical resistance and low thermal expansion (α 20/300°C =3,3*10-6/K) this glass is virtually the only contender for work in the laboratory and it is, therefore, used to date almost exclusively as the glass for laboratory containers and apparatus.
DURAN® borosilicate glass is free from impurities because it is made from selected raw materials.
Even the contamination of analysis solutions is impossible.
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Conditions for safe sterilization
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Various requirements are imposed on the glass and the bottle design for sterilization by autoclaving (see below). The slightly convex curvature of the square surfaces permits good convection when sterilizing since the bottles are only in contact with each other along a line.
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- The glass must be inert to very pure water (i.e. it must not release any toxic substances).
- Sterilization at a temperature of at least 180 °C must be possible.
- Graduation of the possible contents.
- Ease of handling and low space requirement.
- Gas-tight closure.
- Robust for the purpose of reuse.
- Compatibility of various sizes with the same screw-on cap.
- Reprocessing (cleaning).
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Closure system
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Quite a number of requirements are also imposed on the closure system, whereby the screw caps used with these bottles have proven themselves in analytical work and biotechnology in particular:
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- Screw caps and gaskets must be easy to clean.
- Sterilization of the screw cap at 121 °C in the autoclave.
- Gas-tight closure.
- Inert to very pure water.
- Good handling when closing the bottles.
- Not too great a difference in coefficient of expansion between glass and screw cap. Otherwise there is a possibility of the screw cap slightly opening when stored in a refrigerator at +4 °C.
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