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Author Topic: Using the autoclave device  (Read 7882 times)
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Francis Umeoguaju
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« on: April 10, 2010, 07:38:43 am »



Autoclave is an equipment used to sterilize materials to make them organism free. After autoclaving a particular sample or ware it is assumed that most, if not all, contaminating microorganisms are destroyed. 

The autoclave device is capable of raising the temperature of water to 121, at this temperature most organisms don’t survive. Usually the autoclave device maintains its internal temperature at 121 oc for 15 min.  It is mostly used in microbial based investigations to sterilize wares and culture media used in isolating and growing microorganisms.
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haque
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« Reply #1 on: June 16, 2010, 04:05:32 am »


Very important topic. Autoclave is the only sure way of sterilizing any material except those which are heat sensitive. The autoclave heats the water to 121C but it also retains the steam generated by heating the water. This steam builds up pressure to 15 pounds per square inch. Under this much pressure water does not boil and neither do the liquids being sterilized. The autoclave also has a pressure relief valve which opens up when the pressure reaches 15 pounds thus releasing the extra steam.
The autoclave also has two settings; one for slow release of steam after the autoclaving cycle (15 minutes) is completed. This setting is used for sterilizing liquids because if the steam is allowed to escape rapidly the temperature inside the autoclave will be higher than the boiling point of water thus making the liquids boil and spill out of their containers. The other setting is fast release. This is used for sterilizing glassware etc. This fast5 escape of steam prevents condensation of steam on the glassware.
Precautions: Never fill containers more than half for two reasons: One, such large amounts of liquid will require longer than 15 minutes of autoclaving. Two, Start the 15 minutes of timing only after the temperature within the chamber has reached to 121C and the pressure to 15 pounds. Three, when the cycle is complete, let the autoclave cool slowly. Do not open door or use the relief valve to release steam. Four, after the temperature has come down to lower than 100C or even lower and the pressure has come to zero, then open the door but carefully, standing on one side so any steam that may still escape from the door does not burn you. Five always use gloves when taking material out of the autoclave. Six, keep the autoclave clean; don't let water stagnate inside the chamber. Seven, the autoclave is no different than the simple pressure cooker used in home cooking which costs few dollars as compared to the autoclave which may run into thousands of dollars. When using the home pressure cooker, use fifteen pounds of weight and when the weight begins to shake, start timing and lower the heat. After fifteen minutes of sterilizing, remove the pressure cooker from heat and let it cool before opening carefully taking all safety precautions. The pressure cookers also have a safety plug which will pop out if the pressure inside the cooker builds up beyond the 15 pounds. This will happen if the escape nozzle of the cooker (where the weight sits) is plugged up. It is absolutely necessary to keep it clean. One way to know that this nozzle is plugged up is when after considerable amount of heating, the weight does not jiggle. Pressure cooker has one other advantage which the autoclave does not have unless it is the most expensive kind. Pressure cooker comes with different size weights ranging from 5 pounds to 15 pounds. Some liquids such as milk cannot be sterilized at 15 pounds but can be sterilized at 10 pounds of pressure provided we do not put too much milk in the tubes; generally 3 to 5 ml per tube is the best. For this amount of milk you can use 10 pounds of pressure for 10 minutes. After sterilizing let the milk stand at room temperature or put at 37C for a day to ensure that the milk is sterile. Non sterile milk will not stay liquid.

         
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Francis Umeoguaju
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« Reply #2 on: June 17, 2010, 08:03:29 am »


This is a really wholistic contribution. can you suggest reasons why the autoclave pressure valve need not be released immediately after autoclaving, am in the habit of releasing the valve.
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