Electric heating – Microwave heating – Cookware
Patent
1998-10-20
2000-09-05
Walberg, Teresa
Electric heating
Microwave heating
Cookware
219762, 422 21, H05B 680
Patent
active
061146803
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for processing samples in a sealable container which is transparent to electromagnetic radiation, in which method; container. electromagnetic radiation and which is filled with a nonpolar coolant which is transparent to electromagnetic radiation, and
A polar non-solid medium is understood as meaning a medium which is in the liquid state when it is used. It is therefore possible that the polar non-solid medium is in the solid state at fairly low temperatures, for example at room temperature, but the polar-non-solid medium becomes liquid at higher temperature.
DESCRIPTION OF THE RELATED ARTS
The French Patent Application 2,674,146 discloses a device which comprises a cylindrical outer container and a cylindrical inner container. The outer container comprises a vessel and a lid which are detachably joined to one another. The lid of the vessel is provided with a plunger which, when the lid and the vessel of the outer container are joined to one another and the inner container is placed in the outer container, seals the inner container. Both the inner container and the outer container are essentially transparent to microwaves and the outer container is resistant to high pressure. Furthermore, a space is present between the outer container and the inner container into which a coolant can be introduced. The coolant is preferably air, but can also be another gaseous or liquid substance, provided that said substance absorb has little or no microwave absorption. The device according to the French Patent Application 2,674,146 is said to be suitable, in particular, for heating substances under high pressure using microwaves. A disadvantage of said device is, however, that, if a coolant is used which is at a low temperature, for example solid carbon dioxide or liquid nitrogen, condensation of water vapour on the outside of the outer container will occur. This condensed water vapour will absorb microwave radiation during the heating, as a result of which the heating of the substances which are present in the inner container cannot be adequately effected.
It is known that samples, for example soil samples, often have to undergo a processing before the samples are suitable for chemical and physical analyses. Thus, soil samples, for example, are treated with a mixture of concentrated nitric acid and concentrated hydrochloric acid (aqua regia) to dissolve heavy metals present in the sample. Aqua regia is added to such samples and the mixture obtained in this way is heated for a certain time. The treatment is carried out by introducing the sample and the aqua regia into a sealable container which is transparent to microwave radiation. The mixture of the sample and the aqua regia is then heated by exposing the container to microwave radiation. Then the container has to be cooled and the sample has to be subjected to further treatment, such as weighing, decanting, filtering, centrifuging and diluting, after which the contents of heavy metals dissolved in the aqua regia are determined. A disadvantage is that the container has to be made of Teflon. It has been found that such containers have to be vigorously and thoroughly cleaned before re-use, in particular if the containers contain chemically aggressive substances, such as aqua regia.
SUMMARY OF THE INVENTION
The present invention has the intention of providing a solution to the problems and disadvantages cited above. The object of the invention is to provide a method for treating samples, in which method the container no longer has to be cooled after the small vessel has been exposed to microwave radiation. Another object of the present invention is to provide a method in which the further processing steps, such as weighing, diluting and the like, are no longer necessary. A further object of the present invention is to provide a method which can also be carried out on a small scale, as a result of which less chemical waste is produced. Still another object of the invention is that the method can be carried
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Bank Petrus Cornelis
Snijders Adriaan Gerardus
Fuqua Shawntina
Perkin Elmer LLC
Walberg Teresa
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