Leydon, 19th April 1994
The EMS 820 is a user friendly microwave oven for the pathology and histology laboratory, receiving praise from the people using it. It is much easier to program than the H2500, currently made by EBS, and mentioned in the Microwave Cookbook for Microscopists (Kok and Boon). When we wrote the mentioned cookbook, the EMS 820 was not yet available, therefore we could not give a judgement of its practicality for the histology laboratory.
Reasons for using laboratory microwave ovens:
Literally hundreds of laboratory procedures using microwave ovens have now been published including procedures such as heating, fixation, staining, polymerization, decalcification and immunology. Microwaves allow for accelerated procedures in almost each and every step of sample preparation. Not only does microwave technology speed up reaction times (even more important is that it improves the retention of soluble antigens and preserves antigen immunoreactivity better than conventional fixation methods).
KITCHEN VERSUS LABORATORY:
In short, microwaves have now become a standard piece of equipment found in most microscopy labs. Many people feel a standard kitchen oven is good enough and heck if it cooks popcorn just think what it can do to my precious tissue... This is not the case.
Commercially available units, better known as kitchen ovens, were not designed to offer any type of consistency, which is necessary in the lab. The electronics are variable at best, there are numerous hot and cold spots in the oven but most problematic is the function and how the unit operates changes as the electronics and samples warm up. Hence these commercially available units offer inconsistent results and grave disappointment with results when one tries to duplicate the results of fellow scientists using a different commercial oven then his fellow scientists- This is why laboratory microwave ovens were developed - to eliminate the guesswork and offer consistent results from use to use and scientist to scientist.
Laboratory ovens, such as the EMS 820 meet strict clinical standards. They offer reproducible results. They do not damage the sample and they promote the safest handling of dangerous chemicals and infectious agents.
THE MICROWAVE ADVANTAGE:
- Faster fixation
- Higher quality preservation
- Faster staining
- Faster polymerization
- Antigen retrieval
- Faster decalcification
- Rapid drying, etc
Microwaves are electromagnetic waves similar to radiowaves. They have relatively low energy so the myths of "glowing in the dark" are ridiculous. To set the record straight:
- Use a leak detector
- Inspect and clean door seals, frames and hinges
- Disinfect top surfaces
- Oven should be vented to a fume hood
- Use microwave transparent containers
- Use open containers
- Operate the oven with minimum liquid volume
- Use mitts when handling hot containers
- No food in the oven which is used for lab
- No entry of wires or metals
- Do not use caustic agents
- Do not use flammable solvents
- Do not use containers with metal parts
- Do not irradiate closed containers
Microwave ovens rarely leak but monitoring them regularly is advisable for precaution. For protection from leakage these points should be stressed:
- Test the unit frequently
- Increase your distance from the running unit
- Minimise your exposure time, use shortest procedures possible
WHAT NOT TO DO:
- Never operate an empty oven longer than one minute
- Rapid on/off: do not cycle the magnetron on and off by rabidly opening and closing the door
- Do not use auto on programming whereby your unit turns on automatically when the door is closed
- Do not place or run away wires in the oven
- Do not use flammable chemicals (greater than 50% concentration)